My Tractor Forum banner

Replacing the lower drive belt on an MTD 660 series tractor

7K views 100 replies 6 participants last post by  ab1jx 
#1 ·
For a year or so this tractor will hesitate when going forward, but if you back up then go forward that works. I was looking in the space by the gear shift lever last summer and noticed the belts down there are in rough shape so I ordered replacements. But that belt from the bottom of the crankshaft to the variable speed pulley near the transaxle is a dealer-replace item I think. Parts list: http://manuals.mtdproducts.com/manuals/769-00642b.pdf

The main problem is that there are belt keepers. The pulley on the crankshaft has a bolt holding it on, but take that out and nothing happens because that double pulley goes onto a keyed shaft. And there are keepers on 3 sides of that deck under the engine holding the belt on that upper pulley. At least one more on the back end. I suppose I could bend them out of the way but the right approach would seem to be to cob together a puller and take that double pulley off the bottom of the crankshaft. Anybody done this?
 

Attachments

See less See more
4
#2 ·
Welcome to the forum.
Ideally the pulley will slide off the crankshaft when the bolt is removed. I would try a puller first before bending the belt keepers.
 
#3 ·
I'm not sure what I've got for pullers, never had one that worked very well.

No, taking the bolt out did nothing, or some careful tapping around in there with a 1 lb hammer. Impact wrench zipped that bolt right out pretty slick. I could almost cut a pair of wooden wedges and drive them between the big pulley and the deck under the engine. I worry about bending that big pulley trying to get it off. I'll squirt some WD-40 or whatever I can find at that space between the shaft and pulley, let it soak in.
 
#4 ·
Tapping side of shaft part can help. Maybe even heat the shaft. I suggest a real penetrating oil like pb blaster or fluid film rather than wd40. Heat and then spray at top. Those belt guides #34 shoulds screw out. Ends are 1/4 hex usually. But your issue is the guide pieces that are part of the chassis. That is why pulley needs dropped. I have once just bent them way back. Have known people who have lifted engine up to get the clearance from those guides to remove the belt. Not sure why backing up makes a difference. Belts always go in same direction. Transaxle is single speed. Either forward or reverse. Maybe issue is the FNR shifter.
 
#5 ·
I'm going tomorrow to the store to buy a 7/16-20 x 3 bolt (if that's the size). My puller can't deal with a dished pulley so I'll screw in a long bolt to have the bolt in the puller push against, maybe center-drill it in my lathe so they don't sip.

There's at least 1 keeper in the back by the transaxle , I'll probably bend that out of the way. Yes, the screw-in keepers are out, I used to have the snowblower attachment so every year the mower deck came off and the snowblower went on, those keepers always got unscrewed and screwed back in twice a year. The hex is stripped on one, had to use Vise-Grips to turn it this time.

Backing up, I haven't tried to work out the math, but one time I looked in there it seemed like big chunks had come off the inside of the belts, leaving just the backing. They're 17 years old, both original. So by backing up you get onto a different part of the belt. Sometimes shifting up will do it, but you can't always do that.
 
#7 ·
In your case that would not be a dealer replace item. Probably dealer would charge more than your mower is worth to flog that one.

It's quite common for that pulley to become seized/rusted and stuck to the shaft. (not a fun job when that happens) The Keyway is built into the pulley shaft. Sometimes you can lock the engine and take a pipe wrench and wiggle the shaft because if the deck ever hit something hard the keyway jammed in the crank slot. I have had to just sacrifice the pulley and use a very large bearing puller, then get a used pulley from flea bay.

Now days when I find a rough contrary stuck pulley, I just drain the oil out of the motor. drain the gas, remove the battery and turn the tractor upside down, add penetrating oil, let it soak, try pipe wrench, then pulley puller and torch. (you can get too all really easier with the tractor upside down. You can use some padding underneath if you want to keep from scratching up the hood, etc.

When going back use good smear of anti-sieze lube on the engine shaft. If new correct size belts don't make it go check the spring loaded clutch idler pulley area, it should swivel really easy. The center sheave on the variator drive pulley should move up and down freely with the belts off. Sometimes just little bit of oil will free it up and when it's free the belts are easier to install. You can see you tube videos of how it should operate.

When you first install new belts push the rig outside and get ready for a fast launch in high gear. Sometimes it won't even move until you place it in max speed usually #7 on the vari drive and don't try making any adjustments for the lower speeds until the belt have run in.

Replacing those belts is not a fun thing the first time, next time will be somewhat easier.
 
#8 · (Edited)
I had this idea but it took me a while to get around to go buy the bolt. And then it didn't work. I got a 7/16-20 x 3 bolt, made a little depression in the head with my lathe so the puller wouldn't slip off. But the puller is mostly just bending up the edge of the pulley. Looks like the pulley slid less than 1/4" on the shaft, but it's got a long way to go.

Yes, in 17 years the blades have hit things, I've replaced them maybe 4 times, so the key's jammed. I'm about out of time for this year, I need to get the tractor down off blocks and move it so a couple truckloads of wood can go there, then pile that. I've got the front wheels up on a pair of 12" wide John Deere rims. I can actually get under there. But I don't lay on the ground and get up again as easily as when I was younger. Auto part Wheel Vehicle brake Tire Automotive wheel system
 
#9 ·
If it moved a little, squirt with more penetrating oil and tap the pulley back up. Keep doing that until it comes off.
 
#10 ·
If it moved a little, squirt with more penetrating oil and tap the pulley back up. Keep doing that until it comes off.
For the tough ones like you are into I use a husky tough bearing separator puller that is about 4 1/2 inches between the spreader bolts and I have a yoke puller (cross T puller)


I made most of it myself with a cutting torch and welder but HF has a separator at this link.
https://www.harborfreight.com/bearing-separator-63662.html
Turn the bearing separator backwards )concave side up) so as it won't touch the curved bell part of the pulley to keep from damaging the lower pulley's bell shape.

Mine is so tough that I have pulled the lower pulley off of it's shaft collar and then had to weld a piece of metal pipe to the pulley shaft collar to get a bite with the puller and then heat the shaft and collar and hoss it off. If your pulley is already ruined, you can cut the lower pulley off and grind the pulley shaft collar so as to split the shaft collar. or weld a large nut onto the pulley shaft collar as a pusher for a threaded bolt.

If you apply any serious heat you will need to replace the lower sump seal, usually.

Too late now but sometimes you can remove the engine mounting bolts and move the engine just enough to replace the belt.
Best to not bend on the metal frame belt keepers, they will break off.
 
#11 ·
Shh, as far as I know I could still bolt the pulley back on and move the engine instead. This is all the damage I've done so far, bent one side of the pulley out a little. And I just looked back through my pictures, the amount of the inside of the pulley showing around the bolt is about the same as 16 pictures earlier when I'd just gotten the puller arrangement on there and I was showing that it worked. I don't think I actually moved the pulley on the shaft at all, now that I look at that. It looks like it's moved but it looked like that before I started, I just didn't notice.

A cheap new one on ebay at $40 (shipped)
https://www.ebay.com/itm/For-MTD-En...:MT8AAOSwuNNb7Ejy:sc:USPSPriority!01346!US!-1

or new at MTD
https://www.mtdparts.com/en_US/pulleys/engine-pulley---3.12inch-5.56inch-dia./956-04023.html
$78.71 (free shipping because it's over $50)

But to replace the pulley I've got to get it off, pullers and all. To just replace the belt I don't need to. That probably has its pitfalls too but it's uncharted territory.
 
#12 ·
If you have an impact air hammer there's a guy on YouTube who hammers that bolt you put in while holding pulley with pry bar or something to impede its upward movement. Sometimes the pulley just walks down. Principle is that he's driving crankshaft up it's endplay amount .
 
#13 ·
Nope, no impact air hammer, used to use one at a job in the 70s though. No air compressor. I have a Hitachi cordless electric impact wrench but that doesn't seem useful for this. If I spent a year with a regular hammer that might come close. Some kind of slide hammer like for pulling dents maybe.

This is like a bent key in a flywheel in a lawnmower engine I think, and Briggs recommends a puller for those. The weak point seems to be pulling on the edge of the pulley. It's all flimsy.

I wonder what happens if I can make a punch (ground down sheetrock screw) and pound on the key itself. I could only move it towards the engine though. Oiling it from the top would be good, no way to get there. I do have a bottle of 3-in-1 oil with a spout about a foot long. I don't think I can even see the spot I'm aiming for though.
 

Attachments

#15 ·
Well, last night I got 4 bolts out that were holding the engine in, and this morning 2 cords of wood got dumped, the tractor got shoved out of the way by the wood guy, Maybe before snow flies I'll get back to it.

Having the key built into the pulley limits the options. Hack saw blade and cold chisel maybe, split the pulley off and throw it away. I got the bolts out but the engine still resisted moving. The screw-in belt keepers are out but there must be throttle linkage and all that, didn't look up top.
 
#16 ·
On a stack pulley like this one with a small diameter lower pulley sheave,you cant really drill two opposing holes near the hub to put bolts in,so a puller like a harmonic balancer or steering wheel puller could be used--pulling from as close to the shaft gives the most force,without ruining the sheave...in this case a bearing separator as suggested above would be the right tool for the job,IF there is room for it ..it can be tightened onto the hub and not put any pressure on the sheave..




I'd avoid using heat,that will likely ruin the crankshaft seal in the engine base--and hammering on the crank with a air hammer or a typical hammer could crack the crankcase under the flywheel,when the force tries pushing the crank upwards..some WD-40 or penetrating oil in a spray can with the "straw" can get some lube in the area from above..
 

Attachments

#17 · (Edited)
As mention in #10 post the bearing separator is what I use on the tough ones. You will also find that spraying a penetrating lube onto the top of the pulley shaft does not do any good. Briggs has a belled shaft adapter between the top of the pulley's shaft and the bottom of the engine and when the pulley's shaft is all the way up the bell adapter is snug against all.

That is another reason I just prepare the mower and engine for turning the whole rig completely upside down, as previously mentioned and then penetrating oil can then run down the shaft and rest in the key shaft slot. You can then flog the beast more user friendly, even jump up and down on it. I kinda thought maybe you would just make the wood pile on top of the mower until next spring.:tango_face_wink:

If that is a Briggs and you removed 4 engine bolts the engine should just flop around easily on the frame????????? Cables would not hold the engine, they flex.

Here is a link to info about a guy flogging one with issues. Some more info around with a search. You problem is not uncommon, but very disgusting when it happens.

Professional Power Equipment Technicians & Education Network (PPETEN) ? View topic - MTD / Briggs engine pulley problems
 
#18 ·
OK, I can't get to the area above, I can barely see the upper pulley between the sheet metal belt keepers that look like they're part of the tinwork around the engine or something the engine sits on. So I couldn't use the bearing separator either, there's no way to get one in if I had one.

Assuming I haven't ruined the pulley all I'm trying to do is replace the belt to the transaxle. If I can move the engine back 1/2" that should do it.

I've never owned anything fancier than a propane torch which is mostly good for soldering. Pinpoint heat it isn't. I've never accomplished anything using it around engines. Works nice for melting off nylon rope so it doesn't fray. Does a lot of damage usually: fires, burnt paint, etc. Acetylene or mapp gas maybe.

The wood pile, well, it was 2 1-cord loads dumped with a dump truck. I can still get to the front of the tractor but the pile's up against the back. And I'd need to back it out of where it is so it can't go anywhere. It's like a message that I need to move the wood first. Then I need the tractor running to haul the ash barrel off and spread it. I don't want to let the tractor sit apart all winter because parts will get scattered and I'll forget how it goes together.
 
#19 ·
OK, I can't get to the area above, I can barely see the upper pulley between the sheet metal belt keepers that look like they're part of the tinwork around the engine or something the engine sits on. So I couldn't use the bearing separator either, there's no way to get one in if I had one.

Assuming I haven't ruined the pulley all I'm trying to do is replace the belt to the transaxle. If I can move the engine back 1/2" that should do it.

I've never owned anything fancier than a propane torch which is mostly good for soldering. Pinpoint heat it isn't. I've never accomplished anything using it around engines. Works nice for melting off nylon rope so it doesn't fray. Does a lot of damage usually: fires, burnt paint, etc. Acetylene or mapp gas maybe.

The wood pile, well, it was 2 1-cord loads dumped with a dump truck. I can still get to the front of the tractor but the pile's up against the back. And I'd need to back it out of where it is so it can't go anywhere. It's like a message that I need to move the wood first. Then I need the tractor running to haul the ash barrel off and spread it. I don't want to let the tractor sit apart all winter because parts will get scattered and I'll forget how it goes together.
Just so you know.
The LARGE bearing separator when used for such does not go above the upper pulley it clamps between the lower and upper pulley I've got into couple engines that were really rusted so tight that the separator would actually break the lowers pulleys weld loose from the shaft and pull the pulley off it's shaft collar. The pulley itself would still be ok and I could sometimes weld it back on it's shaft later. If the pulleys weld broke loose and the pulley came off I would then have to take a piece of pipe and make a collar to slide over the pulley shaft weld it in place, re-attach the bearing separator and go again. (and this was using penetrating oils and heat)

If you ruin the pulley with careful shopping I've found good used ones on flea bay for $20 including shipping. You have to keep and heads up and make sure that the replacement EXACTLY matches your old one. Slight differences in diameter, distance between grooves, etc. (some of the used ones listed are not by part number and sometimes you can see a MTD part number stamped into the metal on the pulleys. New pulleys and belts will sometimes cost more than the MTD/Craftsman machine is worth. (and you may need other parts on top of that):tango_face_wink:
 
#20 ·
I've been shopping only by part number, I can get a new one from MTD for $78. What the machine is worth is a good question. I bought it new at a Walmart for about $850 in 2002. I'm the only one that's ever used it or worked on it so no bad kludge jobs. I look up parts in the parts diagram PDF, order them from MTD. BUT it's 17 years old, the spindles in the mower deck have some slop. And it's lived outdoors for a few years so the paint's dull and I've had to replace the starter motor twice, maybe because water gets into it. A new one at Walmart is $1700 I think for something close, and I expect to only need it a few more years so I don't want to sink money into another new one. The engine's been good so far but everything else seems to be falling apart. Doesn't use oil.
 
#21 ·
In reference to you mentioning that the engine won't move around with the engine mounting bolts removed.

If you have the 4 bolts out of the engine mounts and the motor is not moveable sideways check the muffler exhaust pipe area. Will have to loosen the muffler mounting. Sometimes you can take out the frame mount muffler bolts and wiggle the muffler down off the slip fit pipe/pipes and not have to loosen the exhaust pipe's flange bolts at the motor. The muffler pipes usually are just a slip fit into the muffler and the muffler shield can be unbolted first and the muffler slid down off the pipes, so as to not fool around with old exhaust pipe flange bolts. Anything in and around old exhaust stuff will have a tendency to want to crumble causing more problems.:tango_face_surprise
 
#23 ·
38racing;12346441[B said:
]do you add any split bushing above lower pulley [/B]around shaft to make sure separator is pushing right in centre of the larger pulley to concentrate force at centre shaft and not pulley sheaves out from shaft? And maybe one could drill holes in lower pulley for the bolts to pass. I do that on stuck rims.
Just a general idea of using a bearing separator on the pulleys.

On a pulley like he is into his lower pulley is about 6 inches in diameter and has a belled top.The top of his pulley is not flat.

When I've decided to get the pulleys off and I already know that I may have to sacrifice the lower pulley I just set the spreader that's pictured in post 16 above the lower pulley with the cupped portion towards the engine take couple of 3/8 inch bolts through the separator holes (not using the threads in the separator holes) using flat washers as backups on the bolts slide the two halves of the separator with the bolts installed as close to the side of the pulley as possible, connect the T puller and start pulling. You will need an assortment of different lengths of 3/8 bolts and handful of flat washers
On the really tough ones the lower pulley may pull off it's shaft and if so I weld on a pipe collar the the pulleys shaft then I can tighten the separator more forcefully and and it will come off then. I try heat/cool etc, but I still have to sacrifice some.

I always keep a crankshaft bolt installed with a concave center drilled head to protect the crankshaft thread and to keep the center bolt of the puller in place.

Some lower 5 1/2-6 inch MTD/Craftsman pulleys have a flat back and you can drill some holes close to the shaft on those to try to not bend the lower pulley and try a steering wheel type puller.

Best to not peck, hammer, hammer Impact or shock load the engines shaft and I do not use a Impact driver on a puller, I go by feel.
I do apply lots of heat sometimes and later replace the lower sump seal. A rule of thumb that I use is, I stop applying heating when I spit on the shaft and it spits back.
 
#24 ·
Well, it's back to wood season until about April. I don't think most people understand that working on a tractor is more interesting than sitting on it riding in circles. I usually sit there thinking of how to build a robot lawnmower, how to make it know where it is. Interferometry https://en.wikipedia.org/wiki/Interferometry is the key I think, use radio around a 6 inch wavelength, the computer in the mower keeps track of how many wavelengths away from at least 2 transmitters it is. Buried antennas, bumping into things, nah.

For the bearing puller I wouldn't have thought of using one that way. Why is that better than just clamping a u-bolt on there? My ultimate way of moving it would be to take a block of about 1/2" aluminum and bore a hole slightly smaller than the diameter of the area between the pulleys. Then a couple more holes to pull from, and turn it 90 degrees and drill 2 more so they go edgeways. Lay it flat again and saw through the center of the circle. Now bolt that hole around the pulley with bolts through the edgeways holes and pull from the pulling holes. Make it as much like a collet on a lathe as possible https://en.wikipedia.org/wiki/Collet with a large area holding to the shaft.
 

Attachments

#25 ·
By this ebay pulley picture there is a small flat place above the lower pulley near the shaft. Something lodged against that you could pull from. I don't have a bearing separator or a t-pulller but these give me ideas of how to rig something up. I didn't know what a t-puller was until I looked it up. There's a type of tap holder that comes apart in the middle. I've got my 3-jaw puller, I need to get something above the lower pulley it can pull on.
 

Attachments

#26 · (Edited)
OK, not very motivated but getting back to it. I got some Torx bits I can use on my battery impact wrench and loosened the exhaust bolts so I can move the engine around a little. Got the belt past those keepers that way.

But now what? The belt isn't going to come down the shaft over the big bottom pulley because there's not enough slack. And there's a crossmember in the way mostly. On the back end I can get the belt around one keeper but it needs to go up over the upper pulley and once again not enough slack.

The belt at left of the front picture is the deck belt, the belt that goes to the transaxle is between the upper and lower pulleys at the moment. The hole in the deck under the engine isn't big enough to get that lower pulley through. I might be able to block the engine up a little and move the belt around more but that probably means taking the throttle cable off it. There's just not enough slack belt to do much with.
2460338
2460339
 
#27 · (Edited)
What is the exact model number of the rig you are working on?

I see what appears to be a VARIATOR pulley in your second picture.
When a variator pulley is involved belt replacement requires tieing the rear idler pullely down with a stout wire so as to give the belt more slack (you can see it swivel as you move the clutch back and forth if the plate mentioned below is removed. and also removng a side mounted shift lever bracket bolts behind the left rear tire, etc. If this is the center FNR type shifter you need to remove the plate that the shifter lever comes up through so as to see the top of the variator, it's mounting bolt, etc..
Summary: Variator drives require getting the belt removed from the most rear pulley first then you have enough slack at the front pulley's without completely removing the drive pulley. (and some manu suggest removing the deck so as to gain easier access, but I've been into enough of them that I leave the deck on. When going back you start with the new belt on the front and just reverse the removal procedure. Sometimes if the center sliding sheave on the variator won't slide up/down rather easily the belts are not as easily installed.
If you cannot find the model number on your machine try searching some you tube videos of replacing the drive belt (front drive belt is called primary and rear drive belt is called secondary) on a 660 series mower that has a variator drive.
With a Model number we maybe can steer you to the EXACT manual for your mower that shows the belt replacement steps.
Them variator drive type belts replacements without any how to's are a pain in the Axe the first time or two. (and both drive belts have to be replaced at the same time even if the other belt looks ok. they have to wear in together or she won't drive and shift properly.

Good luck. (with that old dog) I've walked several miles in your shoes and also Forest Gump's working on them old rusty dogs. Stay calm and safe.

Here is some of Taryls video of belt replacements.
 
#28 ·
Model is 13AM660G752. I've only heard the term variator on this board so there must be some other name for it. On the top of the transaxle there's a pulley maybe 9 inches in diameter, there's a little belt from that to the upper pulley above. I've got that off, got a new one for when I put it back together. The belt from front to back isn't tight with that upper pulley and belt off, but there's only an inch or two of slack. I don't do online videos, my connection isn't fast enough. Maybe I'm back to trying to get that double pulley off the front, I thought being able to slide the engine a little was an alternative. Sliding got the belt clear of the keepers that are bent up (down) from the deck under the engine, that's about it.
 
#29 ·
Here is links to get the owners manual for that rig that has instructions for replacing the belts and adjustments, etc.
This link will allow you to download owners and IPL (parts lists)
file:///C:/Users/owner/Downloads/769-00533b%20(1).pdf



This one is for downloading the actual adjustments owners manual.

file:///C:/Users/owner/Downloads/769-00533b%20(1).pdf

You also have the option of calling or emailing MTD and ask that they mail you the manuals.
Usually takes couple weeks. They are slow at first but will speed up after they answer your email or fone them.
You can find their contact info at the above links.

If you fone/computer is slow you might try going to a library and using their computer and print off the download instructions.????

Summary: Info is readily available and the Servicing info has a lengthy step by step instructions which you are going to need.
It mentions to be careful and not loose the xmission pulley spacer and do not get it upside down when re-installing. (and don't mutilate the yellow wire under the shift lever panel when it;s removed.
 
#32 ·
It's a pain also having to loosen guide pins near the variator pulley. That variator pulley is held on with a c or e clip. Not sure if trying to lift it off will give you the slack you need. I would think that with rear upper belt off that pressing clutch brake forward would give you enough slack. Why not just cut the old belt off. You are replacing it. Then start new one by putting it over lower section of engine double pulley up onto top groove and with engine back on chassis but moved back an inch if possible should give slack to go over the variator pulley
 
#33 ·
I've had 769-00533B.PDF and 769-00642B.PDF around for years, so far everything I've needed to replace I can just look up and order. But the tractor is 18 years old, that probably won't happen forever. I bought it new about 2002. I don't look at the owner's manual much, the parts manual is good. I had the snow thrower attachment with its manuals but it was awful, finally sold it and bought a Simplicity.

I didn't think of pushing the clutch, there's an option to lock it down too. Yes, I could cut the old belt off, but if I can't get it off without cutting it, how am I going to get the new one on? This has 6 forward speeds supposedly but it's all done by changing the thickness of a variable speed pulley. There's no fluid or hydrostatic drive. Sometimes it won't move in the lower speeds but the fix is to put the transaxle in neutral, then move the shifter to the highest speed and let the clutch out. Then put everything back to normal. It's printed on the cover the shift lever sticks through. It usually works, but I'm wondering if this is the hesitation I'm trying to cure by replacing belts.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top