# HSS724 Drive Engagement Clunk



## maxcbrdriver (Apr 13, 2020)

Hi - I recently purchased a used HSS724A ATD, 2016 model year. Everything seems to be in great shape, but I did have a concern about the drive engagement. While the transmission selection is at Neutral and I engage the drive lever, I get a fairly noticeable clunk. I can avoid this if I engage the drive very very slowly, but it's otherwise there. Is this normal to the Honda hydrostatic transmissions? I have the shop manual, but unfortunately it doesn't show the internals to the transmission, so it's impossible for me to know if there is some dog clutch in there that would be expected to 'clunk' in. It sounds very similar to how my Honda motorcycle clicks into first gear when stopped and I know that has dog clutches. My only other experience with a hydrostatic transmission is my Honda lawnmower, but it makes no sounds at all. It also doesn't have a reverse, so I'm not sure if that added complication has something to do with it. Finally, I haven't had the opportunity to use it to actually blow snow yet, so these noises are from about a minute or so after starting it and are repeatable during that time. 

Any comments are appreciated. 

-Matt


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## orangputeh (Nov 24, 2016)

maxcbrdriver said:


> Hi - I recently purchased a used HSS724A ATD, 2016 model year. Everything seems to be in great shape, but I did have a concern about the drive engagement. While the transmission selection is at Neutral and I engage the drive lever, I get a fairly noticeable clunk. I can avoid this if I engage the drive very very slowly, but it's otherwise there. Is this normal to the Honda hydrostatic transmissions? I have the shop manual, but unfortunately it doesn't show the internals to the transmission, so it's impossible for me to know if there is some dog clutch in there that would be expected to 'clunk' in. It sounds very similar to how my Honda motorcycle clicks into first gear when stopped and I know that has dog clutches. My only other experience with a hydrostatic transmission is my Honda lawnmower, but it makes no sounds at all. It also doesn't have a reverse, so I'm not sure if that added complication has something to do with it. Finally, I haven't had the opportunity to use it to actually blow snow yet, so these noises are from about a minute or so after starting it and are repeatable during that time.
> 
> Any comments are appreciated.
> 
> -Matt


no this is not normal. is there anyway you can remove the belt cover and watch the belt engage ? can you locate the clunk area?


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## ST1100A (Feb 7, 2015)

There are "Dogs" on the gears for the steering clutch set-up.
They work like a motorcycle transmission with "Dove-Tails" built on them.
They do wear out and become rounded, causing them to "Jump Out" just like a motorcycle transmission when under a load.
The "Dogs" are on each side, that is what makes it steer by dis-engaging a drive axle.
Hydro-Gear does not show them on their service manuals because they do not offer repair parts for them. That part is "Non Serviceable" and must be replaced as a "Whole Unit".
The Hydro-Gear transmissions are no where near as good as the older transmissions that were built by Honda that were used on the "Non-Steerable" models like the older 624,828 and early 724,928 models.
The old Honda built transmissions were serviceable and much more expensive, but they were built so much more robust and stronger, they were built to last for generations, not "Weak" like the Hydro-Gear units.


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## tabora (Mar 1, 2017)

What's your serial number? Early HSS models had a couple of transmission service bulletins re: slowing due to aerated or low oil levels. May be related and you need the external reservoir fix?

https://www.snowblowerforum.com/forum/1439714-post1.html


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## orangputeh (Nov 24, 2016)

ST1100A said:


> There are "Dogs" on the gears for the steering clutch set-up.
> They work like a motorcycle transmission with "Dove-Tails" built on them.
> They do wear out and become rounded, causing them to "Jump Out" just like a motorcycle transmission when under a load.
> The "Dogs" are on each side, that is what makes it steer by dis-engaging a drive axle.
> ...


you have mentioned this several times. have you had experience with these having problems with so few hours on them? I think the OP said this was a 2016.

BTW I have yet to find an older hydrostatic tranny failure . ( i'm sure they are out there ). The only problem I have seen is blown out seals where the oil leaks out and then the tranny won't work.

In most cases an easy fix pushing seal back in ( when the seals are not cracked ) and bleeding the system. Come across this 3-4 times a winter. Usually because the reservoir cap is on too tight and can not breathe.


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## maxcbrdriver (Apr 13, 2020)

So, the serial indicates it's affected by the TSB and looking underneath, I don't see any expansion tank. As mentioned, the TSB is for ground speed, so who knows whether my symptoms are related.

I have pulled the pulley cover off and as far as I can tell, the idler pulley that the drive engagement lever controls is working as intended. Is there something I should pay particular attention to? The sound seems to originate down low. 

I wasn't aware that Honda no longer made the transmissions for these. That's disappointing. I just checked the Hydro Gear site, do we have the SST?


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## tabora (Mar 1, 2017)

maxcbrdriver said:


> So, the serial indicates it's affected by the TSB and looking underneath, I don't see any expansion tank. As mentioned, the TSB is for ground speed, so who knows whether my symptoms are related.


My suspicion is that the oil level might be low so the actuation is causing the noise? Does it actually drive OK?



maxcbrdriver said:


> I have pulled the pulley cover off and as far as I can tell, the idler pulley that the drive engagement lever controls is working as intended. Is there something I should pay particular attention to? The sound seems to originate down low.


Down low is the SST transaxle...


maxcbrdriver said:


> I wasn't aware that Honda no longer made the transmissions for these. That's disappointing. I just checked the Hydro Gear site, do we have the SST?


Yup, that's it. Been used for years on pro lawn care equipment. The nice thing is that using it obviated the old Honda right-side transmission that is troublesome in old age.


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## maxcbrdriver (Apr 13, 2020)

How would the transmission go about losing oil in the first place though?


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## ST1100A (Feb 7, 2015)

orangputeh said:


> you have mentioned this several times. have you had experience with these having problems with so few hours on them? I think the OP said this was a 2016.
> 
> BTW I have yet to find an older hydrostatic tranny failure . ( i'm sure they are out there ). The only problem I have seen is blown out seals where the oil leaks out and then the tranny won't work.
> 
> In most cases an easy fix pushing seal back in ( when the seals are not cracked ) and bleeding the system. Come across this 3-4 times a winter. Usually because the reservoir cap is on too tight and can not breathe.


Hi O.P.
Yes we had a couple of Hydro-Gear failures with low hours on them.
Some were the pump and motor pistons and cylinder blocks wearing out prematurely, like we see on many many lawn trans-axles, and a couple of worn/broken gear "Dogs" on the steering axle assemblies.
The dove-tails were either broken off or worn to the point that they kept jumping out of engagement when under a load.
The gears looked like they were made of cheap sintered material, something you would never want to see a gear that had to endure a lot of pressure made from.
At least the Hydro-Gear transmissions are very cheap in price to replace, nowhere near the price of the good Honda made transmission.
The only older Honda made hydrostatic failure I saw was on a machine that fell off the back of a truck while it was going down the highway, so the whole machine was kind of destroyed after it was hit by a large truck following behind it when it fell off the truck carrying it.
I saw very few drive pin failures on the right side transmissions on the older models.
The new Hydro-Gear units can't take abuse, like when someone squeezes the steering triggers in and lets them fly out at full speed, like when someone tries to make the machine "Pop a Wheelie" or just running it hard and fast will break them very quickly, and also normal wear and tear will wear/break them rather quickly compared to the older Honda transmission that were built to take a lot of abuse.
Most times Honda covered the Hydro-Gear unit under warranty if the machine was still under it, other units, the customer just paid for the new hydro unit because they were not expensive, rather very cheap compared to the older Honda built units, so the customer did not complain and just paid for it.


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## ST1100A (Feb 7, 2015)

maxcbrdriver said:


> How would the transmission go about losing oil in the first place though?


There were a couple of ways on that transmission.
One was it was under-filled from the factory which has been known to happen from Hydro-Gear.
They used a low grade poor oil in them during manufacture.
The design was a bad design to begin with from not using a reservoir, so it couldn't be checked for proper level and became "Air bound" in many cases.
It did not have enough room in the case to expand when it was hot and forced it out of an oil seal causing a leak that went un-noticed for some time until the operator started having driving/slowing problems with the machine.
They finally figured that it needed a reservoir for expansion and oil level check, so they decided to build it with the reservoir and made improvement kits to re-fit ones on units that didn't come with them after they started to have a lot of problems with them.


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## orangputeh (Nov 24, 2016)

ST1100A said:


> Hi O.P.
> Yes we had a couple of Hydro-Gear failures with low hours on them.
> Some were the pump and motor pistons and cylinder blocks wearing out prematurely, like we see on many many lawn trans-axles, and a couple of worn/broken gear "Dogs" on the steering axle assemblies.
> The dove-tails were either broken off or worn to the point that they kept jumping out of engagement when under a load.
> ...


This does not bode well for experienced Honda owners that were used to working out their machines so hard on berms thinking they were bulletproof.

That pin on drive axle breaks because of the speedshifting owners do at full speed both F/R and because over time the grease gets contaminated due to water entering the case. I have only run into this about 8 times in the last 3 years and hundreds of machines though.

It is my routine now , when doing a service , to install a grease fitting ,andpumping that case full of new grease. And of course trying the educate the owner about what I call "power shifting"


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## ST1100A (Feb 7, 2015)

O.P.
You are correct about the "Power Shifting". That is what normally breaks the pin.
I always tell my customers to start out slow or in neutral, then while the drive is engaged, move the speed control lever to a higher speed position while it is already moving, that saves on the pin.
Honda used a "Bentonite" grease in the right side gear box and there wasn't much in them from the factory in certain years. The Bentonite grease is a good grease, and you are correct about getting moisture into it.
Bentonite was a "Clay" based type grease, most other greases are a "Soap" type base.
Also you are correct about installing the grease fitting to add more grease to them.
Bentonite grease doesn't mix well with other types of grease and should be removed before adding a Lithium based grease to do it right, but most people just pump it in and let it go the way it is without any problems.
If I remember, that pin was a 10mm diameter hardened pin that would break the end off of, and in some cases the shaft would break right at the pin hole, and that was rare but it did happen.
On the new Hydro-Gear transmission, most of the gear "Dog" problems occurred from using the steering clutches engaging and dis-engaging at speed, and the pistons and cylinder blocks wearing in normal use.
You have a good "Routine" by adding the grease fitting to the right gearbox and keeping it full of grease.
This past winter most people's machines didn't get to see much use so we were lucky with not as many break-downs.
You are very right about "This does not bode well for experienced Honda owners that were used to working out their machines so hard on berms thinking they were bulletproof."
Those people who had the older machines were used to the ruggedness of the old machine, and when they got a new Honda, they thought it was just as strong as the old one and they ran it hard, only to break them much quicker, and got very upset by that.


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## tabora (Mar 1, 2017)

maxcbrdriver said:


> So, the serial indicates it's affected by the TSB and looking underneath, I don't see any expansion tank. As mentioned, the TSB is for ground speed, so who knows whether my symptoms are related... I wasn't aware that Honda no longer made the transmissions for these. That's disappointing. I just checked the Hydro Gear site, do we have the SST?


I'd start by checking the hydro oil level and then making sure the linkage to the SST Control Arm is secure... Here's the link to the Hydro-Gear SST Service Manual: https://www.hydro-gear.com/f2ced427ff_sites/hydro-gear.com/files/BLN-0034_P2.pdf


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## maxcbrdriver (Apr 13, 2020)

Assuming it's a fluid level issue, how difficult is it to measure? Am I right in understanding that the transmission needs to be removed? That seems like a non-trivial job. Also, since my unit doesn't appear to have had the expansion tank added per the TSB, are those parts a dealer would have available? I don't see them in the online parts diagrams.


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## tabora (Mar 1, 2017)

maxcbrdriver said:


> Assuming it's a fluid level issue, how difficult is it to measure? Am I right in understanding that the transmission needs to be removed? That seems like a non-trivial job.


Did you look at the Service Manual I posted? Pages 8-9 show how to check the oil level. I don't think it requires SST removal.



maxcbrdriver said:


> Also, since my unit doesn't appear to have had the expansion tank added per the TSB, are those parts a dealer would have available? I don't see them in the online parts diagrams.


 Yes, the parts are readily available. They are right on the Honda Oil Tank parts diagram in the upper left corner: https://peparts.honda.com/powerequipment#/browse/sb/hss/hss724/HSS724A-ATD


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## ST1100A (Feb 7, 2015)

maxcbrdriver said:


> Assuming it's a fluid level issue, how difficult is it to measure? Am I right in understanding that the transmission needs to be removed? That seems like a non-trivial job. Also, since my unit doesn't appear to have had the expansion tank added per the TSB, are those parts a dealer would have available? I don't see them in the online parts diagrams.


Yes it would be difficult because of the location of the cap you have to remove to inspect the level.
You would be better off to remove the transmission to get to the cap and to be able to see down in the case to be able to get a measuring tool in there to measure it properly.
your best bet is to have the oil tank reservoir installed when you do that. That way you can just look at the oil tank and see the oil level.
Once the oil tank is installed, the unit will hold more oil capacity and help get rid of the aeration problems they were noted for.
Another big weak spot on the Hydro-Gear transmission is the drive pulley where it mounts to the pump shaft.
Those pulleys are known for becoming loose and stripping the splines off the inside of the cheap stamped steel sheet-metal pulley. Once that happens, it usually also wears the pump drive shaft along with the splines of the pulley, so you end up replacing both parts.
Normally when that happens you just replace the entire transmission as an assembly because chances are there are other worn out parts in it besides the stripped pulley and shaft.


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## orangputeh (Nov 24, 2016)

ST1100A said:


> Yes it would be difficult because of the location of the cap you have to remove to inspect the level.
> You would be better off to remove the transmission to get to the cap and to be able to see down in the case to be able to get a measuring tool in there to measure it properly.
> your best bet is to have the oil tank reservoir installed when you do that. That way you can just look at the oil tank and see the oil level.
> Once the oil tank is installed, the unit will hold more oil capacity and help get rid of the aeration problems they were noted for.
> ...



I thought Honda was installing these oil reservoirs as part of warranty?


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## ST1100A (Feb 7, 2015)

They would install it if there was a problem with a unit. They have a "Service Update" for it so it doesn't cost them as much to have to re-fit every snowblower that was made, so they don't do it to every unit, only ones that had the slowing troubles that were brought to the dealership.


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## maxcbrdriver (Apr 13, 2020)

Going through the service manual, accessing the top of the transmission requires pulling the engine. Not exactly what I was hoping for.

I may try to run the unit this weekend, run it over a longer distance and see if completely warning it up and putting load on it helps at all. I'll see if I can come up with some other tests to help isolate causes. Calling a dealership is my last resort at this stage.


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## orangputeh (Nov 24, 2016)

maxcbrdriver said:


> Going through the service manual, accessing the top of the transmission requires pulling the engine. Not exactly what I was hoping for.
> 
> I may try to run the unit this weekend, run it over a longer distance and see if completely warning it up and putting load on it helps at all. I'll see if I can come up with some other tests to help isolate causes. Calling a dealership is my last resort at this stage.


if still under warranty then take to dealer. This time of year may not be a long wait.

also . removing an engine is surprisingly easy. a lot easier than removing the hydro unit. It is worth having the Honda shop manual for this machine. less than 50 bucks. worth it's weight in gold.

the first time i removed an engine it took about 30 minutes. now I can do it in about 10. it's all in the shop manual.


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## maxcbrdriver (Apr 13, 2020)

orangputeh said:


> if still under warranty then take to dealer. This time of year may not be a long wait.
> 
> also . removing an engine is surprisingly easy. a lot easier than removing the hydro unit. It is worth having the Honda shop manual for this machine. less than 50 bucks. worth it's weight in gold.
> 
> the first time i removed an engine it took about 30 minutes. now I can do it in about 10. it's all in the shop manual.


Sadly the unit is out of warranty. Makes me wonder if seller knew something was up with it. That being said, I don't recall the noise when I was inspecting it prior to purchase, but perhaps it just didn't register. 

I do have the shop manual. Engine removal does seem pretty straightforward. Oddly, the oil tank is never mentioned.


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## maxcbrdriver (Apr 13, 2020)

How hard is it to remove the steering arms to measure the oil? The manual states that they are likely to break. Unfortunately, they are like $80!


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## ST1100A (Feb 7, 2015)

Max, the manual you probably have doesn't have the oil tank listed because when the manual was published, they did not have a tank in the machine then when the machine was new.
The tank was added later on as it became known that they had a problem with the transmission, and after they developed a "quick fix" for it, it was called a "Product Update".
They had special service bulletins that had the tank installation in it that was only available to the Authorized Dealership at that time. In later years Honda started to produce the machine with the tank installed from the factory, so the newer most current literature would have the tank shown.
An Authorized Honda Dealer would have the updated manual that would show the oil tank.
Years ago Honda used to have Paper Manuals, or service books. Honda does not do that anymore because of the cost of printing the manuals and the paper it uses. Honda is very environmental conscious and doesn't want to kill trees to print books so they have every manual on computer disc now, plus the service literature is constantly updated from Honda online to the Dealership. If they don't update the service literature constantly, the literature expires on their computers and they cannot access them to look at and read on their computers if they are not updated.
The Dealership has to pay a "Subscription Fee" for all the latest most current info, and it is expensive to keep the subscription current and active, which the dealer must do to keep their franchise.
The Dealer can print out the most current book, but it takes a lot of paper and ink, and they are not allowed to sell them to the general public because Honda might not get the money for it, that is in the contract with Honda to have the dealership. But if you know and are friends with the people at the dealership, they sometimes will print out the info you need and give it to the customer, but not too often because that takes work away from their service department.


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## tabora (Mar 1, 2017)

maxcbrdriver said:


> How hard is it to remove the steering arms to measure the oil? The manual states that they are likely to break. Unfortunately, they are like $80!


 You don't remove the steering arms to measure the oil level. Again, as shown in the SST service manual, you just remove the filler cap/breather port (which is replaced when the oil tank is retrofit) and measure the oil height as shown. The reservoir tank retrofit only takes about 1/2 hour, so the engine is certainly not removed; it is accessed from the rear.

https://www.snowblowerforum.com/for...rs/120641d1514330533-ground-speed-hss-res.jpg


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## ST1100A (Feb 7, 2015)

Use caution when working on your transmission. If you have the cheap plastic shift arms and drive pulley, you do not want to break them, which they can be easily broken if not using proper procedures.
Then you might possibly have a long wait for the boat to get here from China with the parts you will be replacing on the unit.
I have the special socket wrench to remove the fill/breather cap on that transmission.
While you are doing that, replace the original cap with the oil tank kit furnished one and install the oil tank.


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## ST1100A (Feb 7, 2015)

The best way to get at your oil fill plug to be able to see everything easily is to remove the engine bed plate from the top of the frame.
Disconnect the drive belts and throttle cables and wires from the engine, then remove the engine from its base plate first.
Then you remove the bolts from the transmission bracket bolts from under the engine base, then the base plate mounting bolts that attach it to the frame sides to remove the engine bed. That way you will be able to see everything and be able to get to the plug much easier, plus it will keep the transmission level to check the oil level.


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## maxcbrdriver (Apr 13, 2020)

I'm a little confused here. The Honda manual says that the oil level is filled and checked via the steering bosses and then goes to make clear that the part is likely to break. Is the breather at the same level as those bosses? Where can I get the special tool mentioned here to open it and then replace with the oil tank compatible one?


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## ST1100A (Feb 7, 2015)

You can make the tool from a socket and cut a groove in it to clear the elbow for the breather tube. It makes the job easier.
You check the oil level through the hole that the breather tube piece-oil fill cap is located at.
You remove that cap and measure down from there. The manual can be confusing to the ordinary/homeowner person on how to do everything. Service technicians understand it better because they work on them everyday.
That transmission was a bad/cheap design to start with. The older Honda transmission used a reservoir that you would fill it from, and could see your oil level at.
Honda started to get cheaper with everything and decided to build their machines cheaper to appeal to the big box store customers who did not want to spend the extra money for a quality built product, so Honda built them for a lower price to get their sales numbers up and they forgot about their old time customers who didn't mind spending the extra money for the higher quality product that Honda used to produce in the past.
Honda didn't care about the problem that was going to happen with the cheaper transmission as long as they got their sales numbers up, then when all the problems started to happen and it hurt Honda's reputation for quality, Honda decided they had to make some improvements to it and they came out with the improved kit that had the oil reservoir.
Honda in their quest to save money, laid off all of the good engineers that they used to employ, the ones who cared about quality and reputation, and that is what happened when they replaced the good engineers with the "Cost Cutting" marketing people who had no common sense, but that is happening everywhere now.
But once you get the engine bed off the frame, you can easily look down into the transmission case once the cap is removed and if you have to, use a thin wooden rod to reach down in to the oil and remove it, make index marks on the stick, and that will show you the oil level that use can use to measure it with.
If you get the oil tank kit, it is measured from the oil tank itself, and is visible from looking at the tank like in the picture Tabora posted.
But to fill the tank you either have to take the engine bed off or use a syringe type tool with a hose on it to get at the fill easier.
The only good thing about the newer Hydro-Gear transmission is the price of it when you have to replace it. You can get them new for around $150 U.S. dollars, where the old Honda transmissions could cost you over a thousand dollars, and chances of ever having to replace the old Honda transmission were slim to none because they were built to last quite a long time.
If you had problems with the right side gearbox, that part was easy to fix and not too many of them ever went bad, usually from severe abuse, and it took quite a lot of abuse before they went bad.


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## maxcbrdriver (Apr 13, 2020)

So, I started it up today, and drove it forward and reverse on driveway a few times to make sure transmission was warned up. At one point, it started going very slowly in reverse.

After all was said and done, I took the following video highlighting the drive engagement clunk I hear. The fist is at 0:02, the second is at the 0:10. On my third engagement, I engaged very very slowly and no sound was made. 

I'll still going to install the oil tank, but figured this was the easiest way for everyone to hear directly what I'm referring to.


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## tabora (Mar 1, 2017)

maxcbrdriver said:


> ...At one point, it started going very slowly in reverse...


If it's exhibiting the Service Bulletin symptoms, I'd approach Honda Customer Service directly and see if they will cover it. There's no mention of an expiration date or need to be under warranty in the Honda SBs. It's an engineering design / manufacturing defect that should be addressed under implied warranty (state laws) in any case.





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## ST1100A (Feb 7, 2015)

That noise does not sound abnormal, that is the belt engaging suddenly from a stop.
Imagine an airplane when it comes in for a landing when the tires hit the ground. From them not rotating to suddenly having to rotate at a high speed they will make a noise like a "squeal/screach" like a "skidding" sound, but much louder because they are larger. Your belt is much smaller so it wont make as much noise, but will make some sound.
That little bit of a "clunk" sound is just from engaging the belt at speed suddenly from a dead stop motion that the belt was in at a stop.


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## maxcbrdriver (Apr 13, 2020)

What's interesting is that the auger engagement does sound exactly as you'd expect, a chirp as the belt slips during engagement. The drive engagement is more like a clunk. Shouldn't they sound the same?


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## ST1100A (Feb 7, 2015)

maxcbrdriver said:


> What's interesting is that the auger engagement does sound exactly as you'd expect, a chirp as the belt slips during engagement. The drive engagement is more like a clunk. Shouldn't they sound the same?


They will sound a little bit different. The auger is much larger with larger parts to get spinning and more inertia to get them moving.
The transmission is much smaller so it will make a different sound than the larger auger, which also uses the auger housing to amplify the sound, like a speaker cone.
The transmission has a small pulley with less resistance to get moving than the auger would have, with larger parts like the impeller and auger tines that absorb some of the drive engagement shock.


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## orangputeh (Nov 24, 2016)

haven't read all the posts.

bottom line......never liked clunking sounds.


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