I have a 1994 MTD 14/42. It has been a good friend for many years but is showing a new quirk which I have yet been able to correct. The lawn is hilly and I use wheel weights and chains. When going down a steep grade in first gear, the rear drive belt jumps off the transmission pulley bringing our mowing to an abrupt halt (and often precarious fix). It appears to have jumped off between the variable speed pulley and the trans pulley via the idler pulley. The belt gets jammed between the top of the trans pulley and frame (about 10:00 looking down from the rear on the trans pulley facing forward). I have replaced the belt. I have no problem mowing on the level, but that is the smallest part of my yards. I have also recently noticed that prior to the belt jump the mower seems to slightly surge faster and then slow, but it is not pronounced as it is only in first gear. Any help/direction/referral appreciated!

 

Check the tensioner pulley. Is it noisy when you spin it? If so, replace it. Also, it is on a somewhat long arm. Sometimes this arm tends to bend upward and be a bit out of alignment with the rest of the pullies. Bend it back to correct alignment if needed. One other possibility is because of the location of the battery, acid sometimes gets on the tranny pulley and it seems that the first place to deteriorate is the thin pulley edges that keep the belt on it. If this is the case, replace the tranny pulley.

 

belt still slips off going downhill. I noticed there were pully cuts from the trans pulley on the idler bracket. I then replaced the shoulder spacer on the bracket but there is still some vertical play. Well, the belt still slips off and I see new pully cuts on the new idler bracket. So now I assume it is the trans pully which is worn/loose (assuming the vertical play in the idler bracket is ok). If this keeps up, I will replace every part a belt touches! So, how do I get that trans pulley off? There does not appear to be a nut underneath so how do I immoblize the pully to get the top nut off?
Thanks for your assistance.

 

I'd be more inclined to say the variable pulley/arm is to blame insomuchas the alignment of such to the tensioner and the tranny pulleys. While it certainly is possible you have a worn tranny pulley, this is not usual.

 

however I replaced the idler pulley, idler bracket and shoulder spacer...but not the bolt. I tightened it well, but it still flexed vertically. I then assumed that was ok...
Am I missing something?

 

Is the belt aligned with the variable drive pulley? Have you driven the mower with the access plate removed so that you can watch what happens when the belt jumps off?

 

OK, this is what happens when I am going down hill, usually on a fairly steep bank, in first gear. It appears that when the speed of the mower is being held back by the lower gear (meaning that it would really go faster than the 1st gear allows if I were to go into neutral), the Idler pully moves all the way out (against the spring tension), vibrates, and then the belt jumps off. The belt jumping off is becominng much easier to accomplish. It even did it on level ground when I switched from 4th to 1st gear (this is a new symptom). Yet if I drive at a constant speed on level ground or up hill, I have no problem.

Hypothesis #5: It's the variable speed pulley!

Two years ago it froze up and finally was forced loose. I have since used anti seize grease on it. I wonder if it is worn and wobbles under load causing the belt to flex and exceed the ability of the idler pully and spring to compensate? I have had some surging in speed before the belt comes off in the past...back when there was some warning to what was to occur.

Thanks for your continued assistance.

 

The bearings in the varidrive pulley could be shot...you might be on the right track.

 

and see what happens. Is there a trick to getting that pulley shaft off? Last time I looked at it, there didn't seem to be much room to get to the nut under the bracket.
Thanks again.

 

I've only done a couple myself and by no means have ne of it commited to memory. Some reason E clips come to mind on part of it...
If you have the model and Serial # of the tractor you can prolly find manuals and IPL here http://manuals.mtdproducts.com/mtd/public/list.jsp

 

Most of these had a snap ring at the top of the pulley shaft. You remove the snap ring and pull the pulley off. If yours is this way, the bearings in it are replaceable. There are 2 needle bearings, I believe they run between 10 and 15 bucks each.

 

Yes, I can get the pulley off (lots of metal particles and pieces), but the shaft also has a flat spot near the truss bearing end and I wonder if it too has been damaged. I am thinking about replacing the shaft, but the nut is under the bracket. How do I remove the shaft, as there isn't much space to get to the nut?
OR, is that flat spot suppose to be there?
Thanks.

 

Without being able to refer to the IPL, which I need the model and s/n from the mower to find, I'm kinda pokin in the dark. I am pretty sure the vari speed pulley assy comes off as a unit and I am thinking it may be on a shaft and have a snap ring also much like the pulley.

 

Model: 134M679G092
Serial: 1D294B80123
That helps thx

Using the illustration on pages 20, 21 of the parts list from MTD, item 94 is a 3/8 bolt that holds the entire variable speed assy on the frame. If you have all the belts and springs removed the assy should come out.
Are there two flat spots on the shaft? Could and open end or adjustable wrench fit?
Things will be much easier with the assy removed and you not standing on your head

 

That's what I did. Removed the bracket assembly so I could get some torque on that nut. Have replaced shaft and pulley with a used unit I found in Ohio. Will install tomorrow provided I can get that spring back on (!) and determine if that is the cause of the belt problem.
Thanks.

UPDATE
That did not fix the drive belt coming off.
But I did find something new after watching the sparks fly when the trans pulley grinded into the idler bracket just before the belt came off. Assuming now it is the transaxle tilting forward when going downhill, I notice that a vertical bolt has unscrewed which holds the front of the transaxle to the frame. I also notice that there appears to be completely missing another bolt (right next to the vertical bolt) which would attach to the tranaxle from the frame horizontally. Unfortuantely, I can find neither of these bolts in my parts manual.
Does anyone know their correct dimensions?

More Info
After removing the vertical bolt, I discover that there are TWO horizontal missing bolts. I can see where the washers were and there are threads (going into the transaxle) but not very deep. At first, I did not see the second one as the vertical bolt was almost out and blocked the view. I can find no reference to these three bolts in my Parts Book.

 

Please see updates in 8-27-06 post. Thanks.

 

If you use the url in my 8-24 post and enter your model # less the last 3 digits and the serial # you can view the entire IPL.
The parts you are asking about are on page 20. There may also be two spacers and a transaxle support bracket. Specific hardware is determined by tire size and deck size. 5/16-18 x 3" or 3.5".

I don't recall any horizontal bolts going into the transaxle...?
I have seen the frame split at the edges of the spacers and allow the axle to rotate enuff to have belt issues

 

The problem with the belt coming off was due to the rotation of the transaxle when going down hill. There are three bolts which attach the transaxle to the frame in the center front. Apparently these bolts are not displayed in the Parts Book. The two horizontal bolts are 1/4-20x.5" while the vertical one is 1/4-20x2". A local mower used parts guy said the vertical bolts were an early version and the vertical came later and that either by themselves would work. As the horizontal bolt holes were mostly stripped, I reinstalled with red locktite (and hope for the best) and used a new vertical bolt. Anyway, it held as I cut the the hills yesterday.
So after replacing two pulleys, a pulley shaft, idler pulley bracket and spring, three bolts did the trick! But I learned a lot and the I needed most of these parts replaced anyway.

 

Dez, I know your post is about 8 years old but it still helped me fix my problem on my 1993 Lowes 14/42 mower. It has been giving me fits for about 3 years with the rear drive belt jumping off when going up or down steep grades or when trying to shift in to reverse. I tried pulleys, belts, you name it, but after seeing your post about the bolt(s) maybe loose or missing I did some checking and found 1 bolt completely gone!. I keep this old mower at a vacation home, so I went by Lowes and picked up the bolts you listed. put in the missing bolt and wow!! No more problems!! I can't MAKE the belt jump off and can't thank you enough. Thanks a million for posting what you found!!

Thanks, Tim C