Peerless/Tecumseh MST Transaxle Help

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2,107
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Appleton, WI
So, I'm now working on a 2004 Toro Wheelhorse garden tractor. It has the Peerless MST 5 speed manual shift transmission, which I think has a few issues. It will work perfect in reverse every time, but it only works sporatically in all 5 forward gears. The only exception is in 5th gear, where it works most of the time but it jumps into gear and does a wheelie on pavement. I almost hit the wife's minivan with it once. I pulled the unit out of the tractor and dumped the gear oil inside in hopes that I'd find that there was little to no oil in it, but about half the capacity drained out. I refilled with 16 oz of 80W-90 and there was no improvement. One other thing it does is when shifting through the gears with the clutch/brake depressed it will randomly pop into a gear and buck forward a bit, which from my limited experience with tractors is what happens when the transaxle is shifted out of neutral. If I then quickly select any gear it will propel forward for a little or even more, but that will be really random as to how long it will continue to move. It even chugs forward sometimes, like it's in gear and moving and then pops out for a second and then pops back into gear again. I've checked all the adjustments and belts, and everything is in good working order. This is proven out in the fact that reverse works every time. Anyone that could provide a diagnosis would be appreciated. Thanks.
 
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1,615
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Watertown, New York
Does your transaxle use "shift keys"? A friend of mine had a John Deere with a transaxle that would jump and skip, and it was the shift keys that were worn out. It was about a $20 fix parts wise, but required a complete dis assembly of the unit.
 

threeputtpar

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2,107
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Appleton, WI
Ugh, I guess not many have ever had to work on one of these 5-speed transaxles. Some extra information if it's any help. In all forward gears, I can pull the machine backwards with a little effort but pushing it forward it moves an inch and then the back wheels lock and slide. In reverse, the opposite happens where it will push forward with some effort and backwards it will lock the wheels and slide. And when I say some effort, that means that I can feel the gears in the trans moving and the axle is not free wheeling like I think it should when the clutch is disengaged. It also pulls backwards in neutral with some effort, but locks the wheels again when pushed forward. Might this just be a linkage out of adjustment? If so, anyone have any pointers on what to mess with?
 

threeputtpar

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Appleton, WI
The more I look into this, the more is appears that you guys might be right about the shift keys. If I mess around with the shifter enough, I can get it to pop into one gear for a little while which would make sense as the shift collar might be just catching enough of the keys to get them to move into at least one gear and then they pop out under load as the collar cannot hold them in properly. I'll see if my friend is interested in me pulling the thing apart and investigating, or if he'll just sell it as is. Thanks.
 
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1,680
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CT
i forget which website but there's a bunch of wacko's out there who race garden tractors and you can probably get a buck or two for that unit. i have a red lawn tractor i rescued out of the woods a while back and i think i posted in here about it. I have pulled the peerless axle apart and put in a set of locking spider gears so both axles were locked. they are pretty simple. I think that gear set cost me like $60, but you can get replacement keys for it pretty easy i think. the unit is easy to pull apart, and use grey rtv to seal the case halves back together.
 

threeputtpar

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2,107
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Appleton, WI
Thank you, yes I found several online options for new shift keys and plan on taking it apart and fixing it up for my friend. He was thrilled that it may only take $25 to get this thing operational and cutting grass again.
 
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1,680
Location
CT
if your are going to tear into it, look for the axle bearings or axle bushings which are an upgrade. the transaxle in stock form the axle just rides against the case. they sell a bushing/bearing to protect the axle and case. I bought my parts from Rom's reworks.
 
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JTK

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Buffalo, NY
As much as I think I can understand all that is mechanical, my brain locks up like a neglected PC when I see the inside of a gearbox. LOL.. Are the shift keys in the groove on the input shaft? I'm clueless on this obviously..
 
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1,680
Location
CT
if you go to tear into one of these, i recommend you make sure you can buy a new pulley that goes on the input shaft on top of the unit- the large one the belt goes around. because most likely it'll be rusted on the shaft and you'll have to beat it off and will bend/damage it. it is flimsy. if you google the peerless mst transaxle you can find and download some pretty good manuals with exploded views. having one in front of you obviously makes things easier to understand, the big pulley that's on top of the unit that the belt goes around is on what i would call the input shaft, not shown in pics. the unit is 5 speed, and has something like a 100:1 reduction ratio in first gear. in pic #3, that gear interfaces at a 90° angle to the gears in the center of the middle shaft. all gears 1..5 are in constant mesh on the middle and near shaft in pic 3. on the near shaft from left to right you can see the gears go from small to large, that's 1..5, with the large gear on other side of shifter being reverse. on that near shaft is the shifter, has the top part of it painted white where it sticks out of the case. when that rotates it moves the slider key in a groove on that shaft and locks one particular gear to that shaft, that's how power gets transmitted.
 
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1,680
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CT
the other thing that comes to mind is there's a detent ball thing on the shifter, and on the top of the case there's an allen head screw that you can tighten down. this forces the ball under spring pressure against the shifter, making it harder to rotate but is what keeps the shifter from rotating left/right on it's own and what keeps a particular gear locked. it's not the slider key that locks the gear.
 

threeputtpar

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Appleton, WI
Originally Posted By: 1 FMF
the other thing that comes to mind is there's a detent ball thing on the shifter, and on the top of the case there's an allen head screw that you can tighten down. this forces the ball under spring pressure against the shifter, making it harder to rotate but is what keeps the shifter from rotating left/right on it's own and what keeps a particular gear locked. it's not the slider key that locks the gear.
Thank you for the great pictures. When you say the slider key doesn't lock the gear, what exactly do you mean? I was assuming that the ends of the two shift keys meshed into the inner cutouts/cogs of the drive gears and locked the gear to the shaft and that transmitted power to the output shaft. The detent ball and spring are solely for the purpose of making sure the shift keys stopped in the appropriate part of the shaft so they would fully engage the drive gears and not pop out of gear. My issue is not the effort it takes to shift, but that nothing engages when I do shift. I can readily feel the detent ball in each of the 5 forward gear positions, so I think it's adjusted correctly.
 
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1,680
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CT
it's been a while since i had mine apart, so i'm going from memory. my biggest point is don't be afraid to tear thing apart, it's pretty simple and once you do you should immediately find the problem. i wasn't sure what your exact problem was, but from what i remember there is the spring and ball that makes the shifter click into each gear. without that you wouldn't know where/when your in a gear but if you loosened that so it didn't click at all you can just swing the shifter front and back moving the slider through each gear. in a given gear under load the slider would stay locked but any free wheeling on the trans where there is no load the slider would move freely- caused by gravity on the tractor shifter lever and vibration. that ball on the shifter lever under spring pressure is important. now if you have the spring set and it clicks and holds in each gear position then most likely the slider key is round off or broken or you have a worn out key way in the gear. going from memory- i think the key has 1 nub for all forward gear positions so if you have nothing forward then most likely it's the key. if you get some forward gears but not others then more likely a broken gear.
 
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threeputtpar

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Appleton, WI
Reviving my old thread with an update. I pulled the transaxle and cracked it open to see what was going on. Come to find out that the shift keys were in pretty good shape for being 10 years old and taking the abuse my friend gives his OPE. I found no chipped gears or shafts, and all of the collars, bushings and spacers were in good shape also. I found no definitive reason for the transaxle to not be putting power to the ground. So, I cleaned it out really well, carefully put everything back together and installed it back in the machine. It now moves forward and backward under its own power. I'm still stumped. One thing I could not figure out was why it will only move a foot or two forward and back when pushed by hand in neutral. It also takes some effort to get it to move those few feet, and then the back tires lock tight. When jacked up, I can spin one wheel forward with ease and the other one will turn backwards so the diff is fine. Any ideas on why it won't roll in neutral? I even pulled the parking brake off and tested it again with the same 1-2 foot results. I think something is binding inside possibly due to being a bit misaligned, but I don't want to pull it back apart again. It operates just fine when running, so will it be OK to run it as is? My friend is probably taking it to his cottage and it may get used 8 times per year to cut his lot there, so not many hours in its future. Thanks.
 
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1,680
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CT
Originally Posted By: threeputtpar
I think something is binding inside possibly due to being a bit misaligned, but I don't want to pull it back apart again.
i remember when putting in the spider locking gears which made the unit a spool... both axles locked, that i had to align those up to the correct gear tooth, otherwise rotating the thing by hand more than 90° it would bind. when you have it correct you can rotate the unit by hand with the case half off... just everything sitting there like in my pics and rotate it by hand forever without it binding. it sounds like you have those spider gears off a tooth, but with it being an open diff in your case i don't know. with it assembled in the tractor engine off belt disconnected, you should be able to rotate everything by hand every which way. lock one wheel spin the other with drive belt disconnected, then other wheel, then rotate input shaft by hand. if you feel it binding pull it apart before you wear it out.
 
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threeputtpar

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Appleton, WI
I was hoping that this wouldn't be the case. When it was apart, I did set all the gears and shafts in the bottom half of the case and spun the gear that meshes with the input shaft and gear and it would all move fine for about a 1/4 turn of the driveshafts and then the large gear on the middle shaft (in your last picture, it's the gear with the silver bushings on each side that have little wings on them to keep them from rotating) would start to lift out of the case half and stop rotating. I thought it was doing this because the other half of the case was not on and when it was bolted together that would hold the gear in place and allow it to continue to rotate. It sounds like the best bet is to pull it back apart and keep aligning the gears until I find the spot where it won't lift out of the case as I turn everything by hand. Thanks again.
 
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Messages
1,680
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CT
Originally Posted By: threeputtpar
When it was apart, I did set all the gears and shafts in the bottom half of the case and spun the gear that meshes with the input shaft and gear and it would all move fine for about a 1/4 turn of the driveshafts and then the large gear on the middle shaft (in your last picture, it's the gear with the silver bushings on each side that have little wings on them to keep them from rotating) would start to lift out of the case half and stop rotating.
that's what i experienced. not good. open it back up. get it so the large differential gear stays seated and rotates smoothly. with the case half off, you should be able to rotate everything easily and it should stay put.
 

threeputtpar

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2,107
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Appleton, WI
So I just need to keep clocking the diff gears until I hit the sweet spot and they all stay in place? Are there any markings on them to line up?
 
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1,680
Location
CT
yes, pay attention to the gear teeth clock one way. if it gets worse then clock other way. if i remember it was kinda hard when they are clocked right to get everything to settle into the case. it'll rotate on you as you drop it in, but once in correctly it'll rotate smooth. i don't remember any markings.
 
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