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RH Variator bearing issues or:learning to cuss in swedish

Cidertom

Cidertom

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Well since the ST is getting a new engine, I decided to fix a few other things since it was out of the way. The first was a "few" wiring issues, wound up doing a 100% rewire. Next was the fact that the drive chains were unequal. OK wound up replacing both. next...

When looking at the manual, the RH (pass side) variator was supposed to have TWO grease hoses. uh oh...
(I also referenced http://www.forumsforums.com/3_9/showthread.php?t=4487&highlight=ST7792 )
Reaching up under the sheave the place that the grease hose sholud be was a hole.. Broken metal. Then removing the assembly revealed the damage to the ST 7792 (index part #47). It's pretty obvious that in the past the bearing didn't. The bearing holder is scored, and the shaft on the lower variator sheave is medium to heavily scored as well. Some one replaced the bearing assembly recently as they are nice looking.

Input from the group please: I'm leaning to JB-welding a hose nipple into the break and building it up with same. The alternative is machining a new part from steel as I see it. Doesn't look like this should be a high stress part. What I think happened: bearing froze causing this part to spin, the nipple smacked against the variator arms and that was that. The shaft is more problematic as the whole thing can shift side to side almost 0.010". Unlike the above reference post my sheave is intact on the bearing plane. so the issue is will it spin concentric or, as it goes around will it have lateral motion as well, which will wear or stress the splines Also troubling is the wear?? on the side of the bearing holder (7792sid.jpg) but the seal isn't worn so either it was that way from start, or it happened before the seal was replaced last.
 

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Is there any chance you could have the shaft welded up and then returned for a tight fit? I have done this before, but not for a Snow Trac variator. This would be the aproach I would take first, since the shaft is not easy to make. Care should be taken to see that you do not warp the shaft while welding. I would use a mig and machineable wire and argon gas. Short welds, on opposing sides with cooling time between welds. The bearing holder I would fix as you discribe. (On mine that greese tube is torn free. To grease it I can rotate the holder around and push the hose on. While holding it there I shoot grease in it.) Then off to the lathe and some cutting tools. Good luck, keep us posted....

Regards, Kirk
 
Another alternative might be Caterpillar bearing set. This green liquid is what they use to set a loose bearing. I think it is probalbly a locktite product. Not sure if it is enough for the loose fit you have. Might be worth checking with a Cat dealership, to find out. BTW they love Snow Tracs at the shop I work with here. I took the mechanics and shop foreman for a ride! Downside its it takes heat remove the bearing. You only have a short time to get it right as this material sets up quickly.

Regards, Kirk
 
I've used the bearing lock a lot (yes it is a locktite product) it works wonders if you are filling concentric gaps. I'm not sure as to it's ability to hold the races in shear.

I may have misled about the shaft: I am referring to the turned section of the cast ST-16B sheave. which fits down in the bearing. From my perspective, the #47,48,49 assembly shouldn't have a radial load at all, just a thrust load as the variator does its thing. But if that's so, why the deep rings in the variator sheave?
 

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I think the rings are there because some of the radial load is on the sheeves. I also think the torrington bearing balls and cage went to pieces and cut the bearing seat area. I would pursue a fix by using brazing to fill the groves with bronze and then turn back to size. If nothing is riding on this area, run it as is. Hard to tell from here. I don't remember just what the fit of this is, but I have had mine apart there before.

Regards, Kirk
 
you may want to get good parts and put the correct bearing in it. looks to me like you have a seal that I don't have.
is the bearing a 3 piece?
jim
 
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JimVT said:
looks to me like you have a seal that I don't have.
is the bearing a 3 piece?
jim
Click to expand...

Yes the bearing is a three piece. The existing seal NTK NE1684 doesn't cross to anything I can find. Going to take a trip to the bearings store tomorrow. The guys there start laughing when they see me pull in. I maintain so much old equipment for the university that I'm there frequently with odd-ball item requests.

The parts breakdown for mine (1978) shows a seal, but that part number didn't cross either.
 
I was kinda thinking that Lyndon once said the late ST's had this seal, but the earlier machines do not. It doesn't show a seal in the exploded view in Cidertom's post above. Would help with the mess a properly geased variator makes for sure!

Regards, Kirk
 
300 H and H said:
It doesn't show a seal in the exploded view in Cidertom's post above. Regards, Kirk
Click to expand...

My Bad, I cut and pasted from a JPEG I found on the site. It was for an older model. I put the drawing more so everyone knew which parts I was referring to. I couldn't get the computer to steal a jeg from the pdf manual for my model year.
 
Not bad at all! We are all learners when it comes to these old machines. I want to soak up all the info I can, the better to be able to service and repair my own! Must have been a small number of machines with the seal update from the factory. Now I am wondering If I might be able to get a seal into my holder to keep the grease mess down.

Regards, Kirk
 
Yes but Jim if you read page two of the links above it will even give the part number for the grease seal as well as the bearings. And better pictures of this set up as well. I suggest you read it then decide what is more to this particular machines issues.

Regards, Krk
 
Cidertom said:
. But if that's so, why the deep rings in the variator sheave?
Click to expand...

Compared the left ST16B to this one. I'm missing just over 3.5 mm of the diameter. at the top (reference to photo). Whether I get a replacement or not, I'm going to fix this one. Now that I know how much, it looks like turn this mess down to good metal and machine a sleeve to fit. At over 3.5mm a sleeve becomes the easiest fix.

The left one is in good shape, except for the bearing which is showing real rust pitting on the ball cage. So I'm going to replace both bearings, both seals and repair or replace the broken bearing holder.

Cidertom
 
Cidertom said:
The parts breakdown for mine (1978) shows a seal, but that part number didn't cross either.
Click to expand...

This was using my SKF reference I have at home. If anyone that has one of these knows a different part number, please share. The OEM part number and the NTK part number is all I have to go on right now. The Bearing is easy.
 
That is a hell of a mess! my read on the damage is the lower flange in the seal carrier cased the grooves when the flange was able to " lift" up into the bottom of the sheave,the angled wear on the carrier corispondes to the wear at the root of the radial webs... somebody got overzealous pumping grease and jacked the carrier up into the bottom of the sheave!
so two questions: what secures the grease flange in place? and if all that missing material made it past that lower bearing was it cleaned out properly when the seal and bearing were replaced or is it still in the lower unit and or transmission? because that repair is raising some doubts.
 
jask said:
so two questions: what secures the grease flange in place? and if all that missing material made it past that lower bearing was it cleaned out properly when the seal and bearing were replaced or is it still in the lower unit and or transmission? because that repair is raising some doubts.
Click to expand...

The bearing carrier with the grease port just sort of floats. It is free to turn, as the arms the push agains it are not attached. On my machine that grease hose is torn off the nipple it is supposed to be attached to. When I grease it, I simply reach up under the left sheeve and turn the bearing holder to where the hose can reach it. Then I put the hose on and hold it while pumping in 10 shots of grease.

The debri from the damage on Thomas's machine could not make it past the tower bearing, and could not end up in the transaxle. Probably spit out the pieces into the belly pan. The sleeve he will turn will be pressed on the root of the sheeve after the damaged section is turned down to cut out the damage. It will be a permanent fix.

Regards, Kirk
 
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did you check the steering shaft ? Is this old damage?
I couldn't get away with ten shots(pumps) of grease.when I did 4 my belt got greasy. Two every season is what I do.
 
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JimVT said:
did you check the steering shaft ? Is this old damage?
.
Click to expand...

The shaft coming out of the tower looks to be intact. It spins easy with no issues I can find. I suspect this damage was before the new bearings went in. But, at that point the damage was done to the 16B variator part. I can easily machine a new bearing housing, but the variator sheave is another story. That is why I'm hoping Don can find a donor one from a st only driven on Sundays to church. I will be repairing the current ST16B but want to have it as the spare if I can.
 
If you spin the shaft your track will move.I am thinking the 3 bolts on the variator or the nut came loose sometime. But you never know.
I added a little locktite and new lockwashers to those 3 when I rebuilt mine.
wait on the bearing maybe your newer one will showup with it.
 
JimVT said:
did you check the steering shaft ? Is this old damage?
I couldn't get away with ten shots(pumps) of grease.when I did 4 my belt got greasy. Two every season is what I do.
Click to expand...


My grease gun is rechargeable and may not put out as much grease as a hand pump gun. I let it cycle 10 times, and never any grease on the belt. There is some grease that gets flung out of the bearing holder, but with no seal, what can we expect? My worry is that with not enough grease you end up with what Tom has with his machine, damaged parts. I can clean up a mess made by a little extra grease, easier than finding or machining new parts. Only two pumps with a hand pump gun per season would not make me very confident that by the end of the season the bearing wouldn't be dry. You should grease it at 50 hours, along with an engine oil change and valve clearance adjustment.

Grease is cheap and effective. If you do not believe, go with out it and you will pay a price.

Regards, Kirk
 
Bell housing mount, I don't think it is supposed to look like this. I thought it was bent metal, but the carrier is straight. I turned a new spacer to match the OEM one last night and will work to find out why the shift. Some one in the past had welded on top of the nuts, but did not weld the bolts. The bolts had been tightened enough that they broke the weld, and or the nut.
 

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this is mine. But I have the orginal style stale air heater for the early snow tracks.
The mount should be the same.
DSC02041.jpg
 
you have a bad motor mount let me look if I have one I will drop it into the box I sand blasted the st-16 b this weekend and painted it it's in the box waiting on my wife to pick it up now. if I have the extra mount I will drop it in too
 
sorry my trans is too deep in the snow just broke an st -11 trying to free it I believe it is just a bug motor mount try averys air cooled there I believe they are in Portland
 
New mounts are in stock at my shop. I saw the rubber earlier and ordered them just in case. I just can't figure out the why of the almost 3/4" displacement. The transaxle looks to be in alignment of the 2x2 cross tube on the chassis. But it's pretty obvious that the mount has shifted.

thanks all,
Tom
 
I would guess that you may have some to adjust the long axle shaft support bolts. AKTIV suggests to adjust those tight enough only to support the outer transaxle tubes the mounting plate looks bent or deformed to.
 
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