My TH350 Rebuild

[crazy4offroad]

One of the hardest parts for me is that snapring but mine slid right off after coming off. You may have to persuade it with a brass drift and mallet then clean it up after you get them separated.

 

[adaml23]

Ok so I made some progress last night and got down to the low/reverse apply piston. Now I need to talk to my buddy's dad and borrow his compression tool to get the reverse piston apart as well as the clutch drums/packs.

I ended up using a pulley puller to remove the planetary gear set off the sun gear. Worked like a charm!

And I'm pretty sure I figured out the main failure with the tranny. Looks like the center support cracked. Also, the roller clutch bearing fell out when messing with it and I think it was bent before I removed it (had to "persuade" it and the center supports to come out as it seemed like they were bound up in the case...).

Any experts want to chime in on the failure reason/cause and let me know if there are any other parts I need to inspect due to this failure? I did a little googling last night before heading to bed and it looks like I may be able to swap in a 700R4/4l60e center support as an upgrade. Any thoughts on this and are there any other pieces I need to put in with it to make it work? Is it worth it or should I just replace with a stock support?

 

[Irishman999]

It looks like the outer race on your one way sprag clutch failed. Swapping a unit from a 4l60 is a direct upgrade for what you have. Might call around town and see if there is any transmission parts supply houses in the area that could hook you up. Another option is a bolt in unit that bolts together in the case, WAY stronger.

 

[adaml23]

I used that and a couple other places for ideas. I set mine up for internal dual feed of the direct drum, doubled up the sun gear bushings (be sure to re-drill the oil holes!) and I think those are the right ones, I'll check my receipt and let you know. Also the hardened intermediate sprag race and if you got the cash the 36 element sprag and hardened input shaft. You can also drill the 2nd and 3rd gear feed holes in the separator plate to 0.125" (1/8") and increase the line pressure just enough to firm up the shifts. Dropping out the check balls makes it hit much harder, which I did but may put them back. There's also a way to have the direct drum piston machined to accept an extra clutch friction and steel but I couldn't justify the cost of machine work vs the gain. I guess the higher the horsepower the payoff might be worth it though. Also use a 0.750" direct drum bushing instead of the stock 0.500" bushing for heavier duty use. Here are the two web pages I referred to a lot, besides the info we have here...
http://www.crankshaftcoalition.com/wiki/T-350_rebuild_tech
http://www.hotrodders.com/forum/t-350-rebuild-tech-145361.html

EDIT: this is the p/n and description of the sun gear bushings...
470-000047632 47632 TH350 Transmission sun gear & rear planet bushing 1969-86.
2 $0.67 $1.34

Re-Edit: I dont see that p/n on their site anymore, might want to call them and make sure.

This may be a dumb question but just wanted to make sure before I screw anything up:

When drilling the 2nd and 3rd gear feed holes, do you drill both the separator plate AND paper gasket? If so, how do you go about drilling out the gasket? Just drill it by itself, or under the separator plate while drilling it out? I just want to make sure before I try to drill the gasket and rip it and screw myself

FYI, everything else has been going good; got it all torn down and cleaned, bushings replaced, new (to me) 700r4/4l60e center assembly/sprag and race. Now just trying to eek out any time I can to work on this thing since we had a new boy about a month ago.

 

[crazy4offroad]

I just drilled the separator plate, the fluid pressure will take care of any difference (if any) with the gasket. Take your time and take pics as you go and post em up!

 

[adaml23]

Thanks for responding. I went down and looked at it tonight and the holes on the gasket are actually already bigger than .125 so I don't need to do anything with them... Probably should have looked into that before I posted last night.

 

[adaml23]

Just a little update. Been busy with the newborn so the rebuild has gone to a crawl as far as progress...

To catch everyone up though, I've got it put back together up to the point where I need to air check the drums/pump assembly. Actually, I tried to check the forward clutch today at lunch and had it hissing at me... I had to head back to work so I didn't have time to look into it more.

I really don't want to tear apart the drums again and already gave back the compression tool but know I could just borrow it again or use clamps if I need to. I'm internally dual feeding it, so would not having that seal on the drum cause it to leak air and negate this test? I didn't sound like a little leak; sounded quite "hollow", or like a big leak, if that makes sense. Also, I put trans jel on the pump sealing rings, obviously, but not sure if it was enough... Any other thoughts on it before I go tearing it apart again?

Everyone loves pics so here are a few of the process (not in order) and some of the different "tools" I've used. The one different picture was taken in my garage as I didn't want to stink up the house while cleaning everything so I moved all the parts out there to clean. Then brought everything back down into the basement.

 

[adaml23]

And more pics...

 

[adaml23]

Last one to show how nicely it was all laid out in order of disassembly after everything was cleaned

 

[frankenstien]

Just a little update. Been busy with the newborn so the rebuild has gone to a crawl as far as progress...

To catch everyone up though, I've got it put back together up to the point where I need to air check the drums/pump assembly. Actually, I tried to check the forward clutch today at lunch and had it hissing at me... I had to head back to work so I didn't have time to look into it more.

I really don't want to tear apart the drums again and already gave back the compression tool but know I could just borrow it again or use clamps if I need to. I'm internally dual feeding it, so would not having that seal on the drum cause it to leak air and negate this test? I didn't sound like a little leak; sounded quite "hollow", or like a big leak, if that makes sense. Also, I put trans jel on the pump sealing rings, obviously, but not sure if it was enough... Any other thoughts on it before I go tearing it apart again?

Everyone loves pics so here are a few of the process (not in order) and some of the different "tools" I've used. The one different picture was taken in my garage as I didn't want to stink up the house while cleaning everything so I moved all the parts out there to clean. Then brought everything back down into the basement.

for the hissing from your fwd clutches, is it the lip seal or coming out of the center of the assembly, ive found that some always seems to leak by the sealing rings. and also make sure your only putting 20-30psi of air to the clutches when testing.

as for the low/reverse support from a 4l60, you should be able to fit in there no problem, i JUST got mine all back together, local shop sold me a used 4l60 support for liek 25$, its thicker than the stock th350 one. i checked clearance with some dimes, mic them, put themin, see if the snap ring fits, gives you an idea on clearance, the spec is pretty large, the diems sound dumb, but thats what the ron sessions book says

 

[crazy4offroad]

Steel ring seals on the pump seal better than the teflon seals, did you use teflon on the pump? If so coat em with trans gel and try again. It sounds like you got everything right. Only thing it might be other than that, it is a real bitch to get those seals tucked in right on the forward & direct drums. If one folded back, or if you were using a fine feeler gauge to tuck it and ripped/sliced it. But if you're 100% with them and you put teflon seals on the pump I would start there. I used steel and mine air checked perfectly, and mine is set up for dual feed.

 

[adaml23]

Well it turns out I just didn't have enough lube on the stator teflon rings and they weren't sealing to the forward drum... I tried putting the metal ones in but ended up breaking the hooks on 2 of them so they're trashed... So I just put the teflon ones back in and called it good.

Moral of the story: Just to be safe, always use plenty of lube!

But after I got that "problem" worked thru, I tried to put everything in the case and when I tried to tighten the pump bolts down, the input shaft won't turn/turns extremely tight! I replaced two different thrust washers and am wondering if they're slightly thicker than the original ones and are not giving me enough clearance and its binding up. I thought I miked them correctly but maybe not... Gonna tear it back down and put the originals back in (they didn't look bad, just figured I'd use the metal ones that came in the rebuild kit instead of the factory plastic ones). Anything else I should look at? FYI, I am positive it got all the drums indexed together as much as they can so I don't think it's that.

 

[HotRodPC]

You say you're certain all the drums and cluthces are indexed properly, but it sure sounds like that is your problem. Unless you replaced the drums or pump with different parts, there's really no reason for this problem other than indexing. If anything, using all the same parts, you'd be to loose on the end shaft play due to worn thrust washers. Just saying, I'd go over that again and make 100% positive all the clutches are properly indexed on their hubs.

 

[crazy4offroad]

But after I got that "problem" worked thru, I tried to put everything in the case and when I tried to tighten the pump bolts down, the input shaft won't turn/turns extremely tight! I replaced two different thrust washers and am wondering if they're slightly thicker than the original ones and are not giving me enough clearance and its binding up. I thought I miked them correctly but maybe not... Gonna tear it back down and put the originals back in (they didn't look bad, just figured I'd use the metal ones that came in the rebuild kit instead of the factory plastic ones). Anything else I should look at? FYI, I am positive it got all the drums indexed together as much as they can so I don't think it's that.

I had a similar problem with the input shaft not wanting to turn and after disassembling I noticed one of the bushings (forgive me but I can't remember which one, maybe one in the stator) was getting galled from the input shaft. I took a scotch-brite pad and scuffed the silver off the bushing to the copper and it assembled easier. It took a lot of time and test-fitting until it was right, and I still had good endplay measurement. It may have actually been the direct drum wider bushing, something was different and required a little clearancing. I had read somewhere that sometimes people will scrape it to clearance it. I wish I could remember which one but it was obvious when I inspected them and could see it galling from the input shaft. Don't know if this will help but it may be something to look for.

 

[frankenstien]

I had the same issue when building mine, bolted the pump doen to check end play, no go. The friction closest to the apply piston was not lined up, the direct clutch drum lugs were flush with the top of the sunshell, they should be 1/8-1/4 below(ish) the top of the sunshell, when i bolted it down, it bent the lugs on that friction.

As already said above, taake it apart and look at the indexing, and make sure.you didnt damage the friction