T20 Band adjustment all messed up - need help!

[tonyk72]

This is on a machine I just purchased, with 75 hrs. The trans is factory original and the previous owner said he had no issue with it before he stored it away 2 years ago due to health issues. I didn't have too much of an opprtunity to drive it...only a few feet forward and back, but did have some trouble trying to steer. This is why I started all this...

I'm following the 10 step procedue to adjust the bands and literally got stuck at step 4. Before I started, I measured the distance at the top plunger at .70 inches and bottom plunger at 1.28. Both were at the maximum extensions. I decided to tighten the bottom plunger and got it to 1.16 inches - what a PITA that was. I then noticed I had zero travel on either plunger!
I started to loosen up th top plunger, but that doesn't seem to have too much effect. The top plunger is also recessed in the bore by about .44 inches. I'm worried that if I loosen it some more the bolt will just come out.

Am I doing something wrong or is something wrong with the T20?

[Mike]

When you say you had zero travel with the plungers after you adjusted them, did you try putting the cotter pin back in and using the brake lever (U channel) to push and pull the plungers or were you doing it by hand? They can sometimes stick a little and be difficult to push in or out by hand.

[tonyk72]

Yes I did. I'm beginning to think that the pin that holds the top plunger in place has somehow got loose and now acts as a stop to prevent the plunger to travel through the bore. Would something like this cause the symptoms I'm seeing?
I've also seen a thread talking about how to be careful when reinstalling the pin because it can also cause similar issues. I've searched all over this site, can't find it...maybe I saw it somewhere else?

[racerone3]

IF someone had the T-20 apart, and IF they didn't get the band anchor pin back in correctly, then it could cause the plunger to lock in it's bore. I can't see how this could happen in a T-20 that has never been torn down, but lets not rule anything out. If the pin is out of place enough to lock up the plunger, the case half is probably toast as the steel pin will have destroyed the aluminum bore. This is typically only an issue when rebuilding one. If you don't get the pin seated correctly, or if you spread the tabs in the plunger that the pin rides in, it can cause a plunger to stick. what I suspect has happened, is that you've pushed a plunger in too far, and the O-ring is preventing it from coming back out

[tonyk72]

Unsure if the T-20 has ever been apart, but the nuts holding the back of it to the frame were not completely secure leading me to belive that the T-20 has at least been out of the machine. The pin on the diamond shifter (same side I'm having issues) looks to me like it has also been replaced.
What would be the best way to proceed? Should I just try to adjust the bands by cranking down on the top plunger bolt? I'm a little nervous about forcing anything not knowing why it seems to be stuck and I really don't want to have to do any kind of exploratory surgery on the T20 if I don't have to.

[whipper-ag]

[hydromike]

There aren't a whole lot of T-20-based machines that are more of a PITA to remove a transmission from than a Max IV, but I'm tending to lean towards everyone else's opinion that you need to yank it. It's a great chance to learn about it, and you could probably have it out in under an hour and fully apart on the bench in two if you're doing it for the first time.

[tonyk72]

Well if pulling the T20 out was the hard part, I guess the rest should be smooth sailing... I just took it out - it really wasn't all that hard. I'm just cleaning up my workbench now and making some space. I'll hopefully crack it open later tonight.

[hydromike]

Loving that dive-into-it attitude. Good luck, and let us know what you find...

[tonyk72]

OK, got it opened up. I stood the T20 upright so that it was standing on the clutch side. I tried pulling off what I guess is the right side straight up, but got my fingers stuck in the brake bands and it didn't come off as clean as I would have liked. But I didn't drop or lose any parts...no big deal. The biggest PITA was removing the C clip. After struggling for 30 mins with various tools and screwdrivers I used a pair of vice grips and clamped them down so that the edge of the vice grips was touching one edge of the C clip. Then with a flat head screwdriver and a slight tap of the hammer on the opposite side of the C clip it came right off.

So here is what I found...you guys were on the right track, it looked like the O-ring on the plunger was causing my issue, but it wasn't protruding all the way inside the case. The back end of the plunger was also touching the brake bands. You can see just the edge of the O-ring in this pic:


Here's another pic where I managed to pull on the plunger and now the O-ring is just inside the bore.


Last pic where I was able to pull the plunger to where it is about 1/4 inch away from being flush with the outside of the case.


Knowing what I know now, I probably could have just adjusted the top plunger by cranking down on the bolt. But at least I have peace of mind. I think I should be all set now? I just have to put everything back together.

[racerone3]

before you put it back together, pull the drums and bands out. remove the O-rings from the plungers and then push the plungers through the bores to make sure they slide freely. also check the bores for scratches, or groves (they can be cleaned up with a brake hone if need be). Stop by Lowes or a similar hardware store and pick up a pack of #30 O-rings from the plumbing section. When you put it back together, push the plungers all the way through the bore and install the new o-rings from OUTSIDE the case. lube the o-rings with some atf and slide the plungers back in a little. install the c channel tightening the adjuster bolts just enough that the plungers can't go in far enough to let the o-ring fall inside the case. then set your drums back in. (it can be a pita to get the sun gears, plate and thrust washers aligned properly... just take your time).

[tonyk72]

OK, I pulled the problem plunger through the front of the case, removed the o-rings (which looked fine - no nicks) and put the plunger back in. It moved freely in the cylinder bore with no issues. I didn't see any scoring either. I took it back out from the front and installed the new o-rings. I did the same for the other top plunger too. I also measured the thickness of the bands (just for the ones attached to top plungers) and they were both about .1 inches thickness. I tightened the bolt on my top plunger and noticed it still wouldn't come flush. But everything looked good - maybe the band is just a tad bit short or the drum itself is a tad bit thick? I decided to just put everything back together and something looked a bit wierd to me:


It was about 1AM when I did that, fortunatley I didn't struggle to get it like this. After laughing at myself and finally getting it back together the correct way, I adjusted the bands. My problem side is still at most 1/4" total travel - not 5/16". The other side is fine at 5/16".

Should I just run it? Any good way to do a dry run test to make sure nothing will explode?

[demo61x]

lol that sucks, done some dumb **** like that myself before. need sleep!!!!

[amphibious drew]

I have some decent bands I took out of my tomohawk because one band was longer than the others. I could sell you the longer one and an extra one if you want to try them out.

[tonyk72]

Almost done

The T20 is back in. I was spinning the sprockets in forward, neutral and reverse and noticed that my left side, in reverse, the sprocket has little to no resistance. Is this normal?