# Drive slipping?



## BTodd

I have an older Craftsman II 8/25 model 536.886800 in my garage this week. While going through all the controls, I noticed there wasn't much power to the wheels. I can engage the drive wheels, hold it back, and the usually the tires can turn, breaking traction even on bare pavement. Most other machines the tires will spin even on bare pavement if you hold the machine back with the drive engaged. I checked the friction disk. It had a bit of glazing so I held some sandpaper to the rubber and spun the wheels to get down to fresh rubber again. There was still plenty of rubber left on the disk. Then I took some steel wool to the friction plate and got that all shiny again. No oil or grease on the disk. The drive belt is tight and in decent shape. Idler pulley is keeping good tension on the belt. Is this common for some machines to not have the same amount of power to the ground as others?


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## micah68kj

Check your belts and drive disc.


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## bad69cat

Take a look at the driven gear (#57) and how it meshes with the axle gear......
MOTOR MOUNT ASSEMBLY REPAIR PARTS Diagram & Parts List for Model 536886800 Craftsman-Parts All-Products-Parts | SearsPartsDirect


Does it look in good shape? If so, then look at the bearings on the shaft ends of the driven gear and see if they are shot......


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## BTodd

Bearings are surprisingly good. The gears mesh well with nothing abnormal underneath. Everything actually turns rather smoothly. I did have to work on the speed selector mechanism to make it work freely, but that's working like a champ now. With the engine off and drive clutch engaged, the tires will not turn and there is no slippage. I'm starting to question the drive belt as its next most likely culprit.


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## Curtis328

I'm having the exact same issue with an older Craftsman; did you ever find a resolution?


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## HCBPH

Curtis328 said:


> I'm having the exact same issue with an older Craftsman; did you ever find a resolution?



Different model but similar issue. Check the obvious: belts for glazing and dimensions, tension, pulley build-up, friction wheel and disc. Now also check both bushings on the friction disc shaft. Seem them wear and the disc will move when drive is engaged and loses power to the wheels.


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## Curtis328

HCBPH said:


> Different model but similar issue. Check the obvious: belts for glazing and dimensions, tension, pulley build-up, friction wheel and disc. Now also check both bushings on the friction disc shaft. Seem them wear and the disc will move when drive is engaged and loses power to the wheels.


Thanks for your excellent input!

- Installed brand new drive belt (properly-sized) one week ago

- Belt has adequate tension, and does not slip when the wheels stop moving

- Drive engagement cable is adjusted as tight as possible

- Installed brand new friction wheel one week ago

- Friction disc has been cleaned with isopropyl alcohol, and does not have excessive play in its bearing

- Replaced both friction wheel shaft bushings today, as the one on the left (driver's) side was badly worn. Shaft is nice and tight now.

- Need to figure out a (safe) way to lock the axle shaft from rotating, with the machine on jack stands, to see exactly where the power is being lost


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## Curtis328

HCBPH said:


> Different model but similar issue. Check the obvious: belts for glazing and dimensions, tension, pulley build-up, friction wheel and disc. Now also check both bushings on the friction disc shaft. Seem them wear and the disc will move when drive is engaged and loses power to the wheels.


When you say "pulley build-up", are you referring to worn belt material bonded to the groove in the pulley?


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## Shaw351

I would remove the bottom belly pan, move the machine to the edge of a building or a fence post that will not move when forced upon, carefully Engage The Drive lever with engine running at low rpms and see where the power is being lost. From all the work that you've done so far... I'm guessing there's not enough tension on the friction wheel to the friction plate, or something else is worn on the friction wheel assembly allowing it to not have enough tension. Sometimes brand new friction discs have to be sanded or ground in the center because there is a high spot which allows slippage when it is engaged against the friction plate, even though it is brand new it still slips. Please let us know what you find.


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## HCBPH

Curtis328 said:


> When you say "pulley build-up", are you referring to worn belt material bonded to the groove in the pulley?



Yes. If the belt is not staying snug against the pulley and is slipping, belt material can be left on the inside of the pulley causing it to slip worse. Brake cleaner and a wire brush does well on removing that buildup, but be careful as brake cleaner can remove paint.


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## Curtis328

Shaw351 said:


> I would remove the bottom belly pan, move the machine to the edge of a building or a fence post that will not move when forced upon, carefully Engage The Drive lever with engine running at low rpms and see where the power is being lost. From all the work that you've done so far... I'm guessing there's not enough tension on the friction wheel to the friction plate, or something else is worn on the friction wheel assembly allowing it to not have enough tension. Sometimes brand new friction discs have to be sanded or ground in the center because there is a high spot which allows slippage when it is engaged against the friction plate, even though it is brand new it still slips. Please let us know what you find.


Well, I followed this to a tee...

It's the friction wheel that stops spinning. The friction disc continues to rotate, concentric with the traction drive pulley.

So clearly it's a friction issue between the friction wheel and the friction disc. I do believe that if I could apply more force with the disc against the wheel, it wouldn't slip, but as I mentioned, there's no more adjustment I can do. The traction clutch pivot mechanism (the triangular bracket with 3 holes, which attaches to the traction clutch bracket and the traction drive cable) reaches the extent of its travel, and is limited from further travel by the blower's frame itself. 

I believe that if the traction clutch spring had a greater spring-rate, it would compress less, thereby applying more force to the friction wheel.

Is it possible that I'm expecting too much from the drive mechanism? Should the traction drive assembly be able to slow down the engine's rotation before causing the friction wheel to slip, on a properly running craftsman machine of this era? (C950-52677-9, from the mid 80's)


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## nwcove

under normal circumstances, the wheels should spin . have you tried cleaning the disc and wheel with gasoline or acetone etc ?


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## Curtis328

nwcove said:


> under normal circumstances, the wheels should spin . have you tried cleaning the disc and wheel with gasoline or acetone etc ?


I've cleaned the metal friction disc with 99% isopropyl alcohol. Should I clean the rubber friction wheel as well? and use gasoline or acetone this time?

Also keep in mind I have tire chains. Would you still consider this normal circumstances, and think that the tires should spin, say on a surface like grass?


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## Shaw351

Im not to familiar with your particular drive as i do mostly ariens, but all drives are similar in function. Some move the friction wheels and others move the drive plate. Could you post up a few good pictures of the traction drive and the adjustments you speak of. Might help us with finding your problem. Im sure with the think tank we have here you will be up and running quickly. 
I had a similar issue with a friction plate that moved towards the friction wheel but acted like your problem, no matter how much adjustment i did. What i found to be the problem was even though the assembly was moving to the wheel, it was rusted internally and had soo much resistance after contacting the wheel the spring would just stretch and give no more tension to the wheel. I disassembled and cleaned all moving parts, lubed up and it's a tank now.


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## Curtis328

Ok, here is my 8/25:


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## Shaw351

Great pixx Curtis, 

I see one thing you can adjust, looks to be at least an inch of adjustment on the cable end attached to the spring on lever. I would also remove the cotter pin on the rod closest to the drive pulley, push rod out of arm bracket, then move that arm bracket towards the rear of machine to check three things...

First see that it moves freely & easily, ive had these assemblys rust up inside the bearing housing, They can move a little, but sometimes not enough. You can remove bolts on the friction wheel to allow the friction plate more movement for testing and also allow the lube you spray on that whole assembly to get worked in.

Second look to see if it moves enough but make sure it does not come into contact with the axle, from the pixx it looks like it is not hitting, which is good.

Thirdly check to see that the drive pulley or back of its hub is not bottoming out on the housing or a bolt head when it is being pulled rearward moving the drive plate rearward into the friction wheel. 

Everything looks good and to be in nice shape, hopefully its just the cable adjustment. Let us know what you find.
If all that checks out, only other thing I can see is that spring assembly on the arm, check its moving ok.


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## Curtis328

Shaw351 said:


> Great pixx Curtis,
> 
> I see one thing you can adjust, looks to be at least an inch of adjustment on the cable end attached to the spring on lever. I would also remove the cotter pin on the rod closest to the drive pulley, push rod out of arm bracket, then move that arm bracket towards the rear of machine to check three things...
> 
> First see that it moves freely & easily, ive had these assemblys rust up inside the bearing housing, They can move a little, but sometimes not enough. You can remove bolts on the friction wheel to allow the friction plate more movement for testing and also allow the lube you spray on that whole assembly to get worked in.
> 
> Second look to see if it moves enough but make sure it does not come into contact with the axle, from the pixx it looks like it is not hitting, which is good.
> 
> Thirdly check to see that the drive pulley or back of its hub is not bottoming out on the housing or a bolt head when it is being pulled rearward moving the drive plate rearward into the friction wheel.
> 
> Everything looks good and to be in nice shape, hopefully its just the cable adjustment. Let us know what you find.
> If all that checks out, only other thing I can see is that spring assembly on the arm, check its moving ok.


Unfortunately, even if I further adjust that cable attached to the spring, the black metal pivot mechanism (shown front and center in my third picture) cannot travel any further, it hits the snowblower's frame when you press down the drive-engagement handle. So at this point, it would make no difference if I pulled on that cable with a crane, the pivot doesn't allow any further travel. The pivot that I'm referring to is the black piece that passes through the frame. The cable is attached to one end of it, and the other end is attached to the engagement arm with the spring and cotter pin on it.

I actually just had everything under there disassembled (for the purpose of troubleshooting this issue), and everything seems to function smoothly. Nothing binds or makes contact with other parts throughout its full range of motion.

It seems as though when you pull the handle to engage the friction wheel, the cable does its job and pulls the black pivot bracket (which passes through the frame) up to the extent of its range of motion, this pivot bracket pulls up on the engagement arm with the spring on it, which pulls the friction disc up against the friction wheel. The engagement arm with the spring on it compresses the spring in the process. If this spring were infinitely stiff, all of the linear motion of the arm would be transferred to the linear motion of the friction disc. On the other hand, if the spring were infinitely weak (zero spring-rate) none of the linear motion of the arm would be transferred to the linear motion of the friction disc, and the friction disc would not move. That spring seems to act as a sort of "clutch" mechanism, cushioning the friction disc's contact with the rubber friction wheel.

The way I see it, my only two options are this (and I don't like either of these options, because I don't like for things to be jerry-rigged):

1) Replace the heavy compression spring on the engagement arm (vertical spring in my fourth picture) with one of a higher spring-rate (stiffer spring). This would allow more of the linear motion of the engagement arm to be transferred to the linear movement of the friction disc

2) Enlarge the opening in the frame, to allow the pivot mechanism to extend further up when the handle is pressed down (The pivot mechanism can be seen clearly in my third picture).

Hopefully this all made sense.


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## Shaw351

If your willing to experiment..... You have more options !!!

There seems to be a big gap / space between plate and wheel, which is using up all your adjustment travel. 

Suggestions.....

Is that arm that moves the plate welded or bolted ??
If bolted it might of slightly moved which will cause your adjustment issue, loosen and tighten it closing up the big gap so there is only an air space. 

If welded it would have to be ' Tweaked '. 

Other option is to add a flat washer between the friction plate and the shaft it is threaded on to closing up the big gap. It is possibly a left hand thread as ariens are, but I've not worked on a craftsman like yours. 

See what you feel comfortable doing. Were here to help. 

Since you have not had it from new, somebody might of bent the friction plate arm, or had the plate assembly apart and had a leftover washer / spacer to hang on the wall. 

Let us know what you figure out.


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## Curtis328

Shaw351 said:


> If your willing to experiment.....
> 
> There seems to ba a big gap / space between plate and wheel, which is using up all your adjustment travel.
> Suggestions.....
> Is that arm that moves the plate welded oe bolted ??
> If bolted it might of slightly moved which will cause your adjustment issue, loosen and tighten it closing up the big gap so there is only an air space.
> If welded it woukd have to be ' Tweaked '.
> Other option is to add a flat washer between the friction plate and the shaft it is threaded on to closing up the big gap. It is possibly a left hand thread as ariens are, but I've not worked on a craftsman like yours.
> See what you feel comfortable doing.
> Since you have not had it from new, somebody might of bent the friction plate arm, or had the plate assembly apart and had a leftover washer / spacer to hang on the wall.
> Let us know what you figure out.


Excellent ideas Joe!

I'm going to look into those possibilities tomorrow.

Again, thanks for all your input.


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## Shaw351

Curtis328 said:


> Excellent ideas Joe!
> 
> I'm going to look into those possibilities tomorrow.
> 
> Again, thanks for all your input.


No Worries :icon-cheers:


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## BeerGhost

I also notice the "shine" on the friction plate. ruff it up to break the glaze.
Will help with more grab for the disc.


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## Shaw351

Have we made any progress on this machine repair, im curious to see what the outcome is. I love the chase & challenge of broken things. It keeps us Tinkerers going !!


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## Curtis328

No progress yet.

I'm going to try roughing up the friction disc, but I still think that there isn't enough pressure being exerted on the friction wheel by the friction disc.

I find it strange that the old rubber friction wheel that I replaced had essentially no wear on it.

I think Shaw351 may be onto something; maybe a previous owner had the machine apart at some point, and forgot to install a washer or something that would have held the friction disc closer to the friction wheel when the handle is released.


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## guyl

If the control cable going to the drive mechanism has a large spring in line with it at the bottom end, you want to adjust the cable tension so that you can see the large spring start to stretch a bit when you fully depress the drive handle. Initially the drive handle is stretching a smaller spring inside the transmission until the plate contacts the wheel. You want the drive handle to have traveled about 3/4 of it's way when contact happens, and to be stretching that large spring for the last 1/4 of it's travel.


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## Curtis328

guyl said:


> If the control cable going to the drive mechanism has a large spring in line with it at the bottom end, you want to adjust the cable tension so that you can see the large spring start to stretch a bit when you fully depress the drive handle. Initially the drive handle is stretching a smaller spring inside the transmission until the plate contacts the wheel. You want the drive handle to have traveled about 3/4 of it's way when contact happens, and to be stretching that large spring for the last 1/4 of it's travel.


Yes, the cable tension is definitely high enough. Any more tension and the drive mechanism engages without even depressing the handle...


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## guyl

Ok, and is the friction wheel easy to turn by hand? Do the gears and the wheels turn freely or do you feel any resistance? If it's a chain drive instead, is there a lot of loose in the chain, allowing it to climb up on the sprockets and maybe jam?


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## merdody1

I had slippage at the wheel due to snow melt bringing moisture and oils down on the friction wheel. Only under heavy load and doing the heavy wet snow at the bottom of the driveway. I made a cap out of a vinyl stair tread and screwed it into the top of the shear pin storage compartment. It really helped my wheel slippage.


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## Curtis328

guyl said:


> Ok, and is the friction wheel easy to turn by hand? Do the gears and the wheels turn freely or do you feel any resistance? If it's a chain drive instead, is there a lot of loose in the chain, allowing it to climb up on the sprockets and maybe jam?


Yes the gears mesh very well, and turn smoothly.


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## Curtis328

merdody1 said:


> I had slippage at the wheel due to snow melt bringing moisture and oils down on the friction wheel. Only under heavy load and doing the heavy wet snow at the bottom of the driveway. I made a cap out of a vinyl stair tread and screwed it into the top of the shear pin storage compartment. It really helped my wheel slippage.


My testing is very controlled; heated garage, and therefore no water/snow on/in the snowblower.


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## Taurus04

From a recent thread on the same issue I think.

Check the trunion bearing under the friction plate as well. When it wears, the drive plate can wobble when pressure is placed on the friction wheel. My OPE repairman tells me that is what sends most of the Murray built Craftsman blower to the scrapyard. A sure symptom is when you hit a tough snow pile the blower will stop going forward and reverse itself.

If the drive plate moves down, that could be causing your lack of power.


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## Curtis328

Taurus04 said:


> From a recent thread on the same issue I think.
> 
> Check the trunion bearing under the friction plate as well. When it wears, the drive plate can wobble when pressure is placed on the friction wheel. My OPE repairman tells me that is what sends most of the Murray built Craftsman blower to the scrapyard. A sure symptom is when you hit a tough snow pile the blower will stop going forward and reverse itself.
> 
> If the drive plate moves down, that could be causing your lack of power.


Friction disc trunion bearing has essentially no play; thanks for the insight though.


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## Curtis328

This is not an obvious one...

I've been chasing this problem for 3 years, since I inherited the blower from my uncle.

Being a mechanical engineer, as well as a certified mechanic in a past-life, I consider myself somewhat mechanically competent.

I'm guessing someone had this machine apart in the past, and failed to re-install a washer or spacer which would have allowed the friction disc to naturally rest in a closer position to the friction wheel (when the handle is released). As I've mentioned, the engagement arm (bracket that the drive cable is attached to) reaches the upper limit of its travel, and is prevented from further travel by the frame of the blower.

Unfortunately the parts manual for this machine (C950-52677-9) is apparently unobtainable in any form. I do have a manual for a close (albeit different) part number; but I can't be certain if this machine is missing any parts or not without the actual manual for this machine.


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## Taurus04

I have a Craftsman 8/25 Model C950-52677-7. If I aim it at a large snow bank - end of driveway, it will eventually stop moving forward. At that point I stop as I do not want to smoke the belts or chew up the friction wheel. I have done both in the past. I also have a 10/32 Craftsman made by MTD. If I aim it at the same bank and try to bog it down , it will stall. Maybe the difference is in the transmission/friction wheel design. The Murray built C950 is a lighter design.

There are a few other 8/25 owners on the forum. Maybe they can provide input.


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## Curtis328

Taurus04 said:


> I have a Craftsman 8/25 Model C950-52677-7. If I aim it at a large snow bank - end of driveway, it will eventually stop moving forward. At that point I stop as I do not want to smoke the belts or chew up the friction wheel. I have done both in the past. I also have a 10/32 Craftsman made by MTD. If I aim it at the same bank and try to bog it down , it will stall. Maybe the difference is in the transmission/friction wheel design. The Murray built C950 is a lighter design.
> 
> There are a few other 8/25 owners on the forum. Maybe they can provide input.


Thanks for that input! Helps when someone has a similar machine.

The strange thing is my friction wheels never wear. There's never any rubber adhered to the friction disc, and never any rubber shavings sitting on the access panel. I replaced the last friction wheel that had been on there for many years, thinking maybe the rubber had hardened, the new one had the same amount of rubber on it, and made no difference to the drive.

This is why I'm feeling that the friction disc isn't engaging the friction wheel hard enough.

Does your metal friction wheel have rubber from the friction disc adhered to its surface? Also, is your metal friction wheel smooth and shiny, or rough and dull?


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## Taurus04

My friction disc is not overly rough or smooth and shiny. It does have a bit of tooth to it. I had to replace the disc when the impeller iced up and I chewed the belt and disc. The problem with mine is that the drive shaft bearings were installed backwards by the previous owner because the wheels were seized on. It caused the friction disc to skate as the shaft moved from side to side due to free play. With the slop taken out of the shaft, the machine runs like new. I never had first or second gear when I first got it.

Are you trying to stall it in 1st or 2nd gear? Maybe the wheel is skating to neutral when this happens if there is a lot of free play.


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## Shaw351

Bump..... have we made progress on this drive issue ?? 
Very curious to get it resolved and up and running.


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## JayzAuto1

GEvening Curtis, I've been following this thread, waiting for the final chapter. Hard to 'See" what's really wrong here. But I have a few styles of that machine, in different configurations, sizes, style, colors and names. But, the one thing they all have in common, is the way the spring is installed on the actuator. This may or may not have an effect, IDK, but they all have great pulling power. If you look at the spring, where it attaches to the actuator, it appears to go BEHIND, the actuator pin, then curl around toward the operator an up and over. On the units I have here, the spring is reversed..... Meaning that it goes around the BACK of that pin, and curls up and forward, towards the front. Is it possible to just spin the spring 180*?? Would that give it more 'throw'? Just a suggestion. I'll go out in the yard at lunch and grab some pix in a little bit. GLuck, Jay


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