Th350 rebuild (lost drive gears)

[Davidj]

Made a thread a couple weeks ago about running dry on atf and losing all drive gears. Community said “yank it for overhaul” well, I’ve got it torn apart and I’m not sure where the issue was. I have a couple pictures to share and ask opinions on. One is of all the clutches. The ones up top seemed burnt looking but I’m not sure if that’s enough to have caused me to lose drive gears completely. Next is the valve body. When disassembling, one of the valves were pretty difficult to get out. Took quite a bit of turning and pulling when all the others slid out easily. I took a picture with the valve sticking out of the slot that was being a pain. Maybe this was the issue? I appreciate any and all input. Simply asking opinions on what could’ve been the culprit for no drive gears.

 

[Davidj]

If closer pictures of any other parts are needed, just let me know. May have to describe mentioned part in laymen’s terms though.

 

[Matt69olds]

The clutches have definitely seen some heat, but they aren’t burnt. What’s the pump look like?

 

[NickTransmissions]

Made a thread a couple weeks ago about running dry on atf and losing all drive gears. Community said “yank it for overhaul” well, I’ve got it torn apart and I’m not sure where the issue was. I have a couple pictures to share and ask opinions on. One is of all the clutches. The ones up top seemed burnt looking but I’m not sure if that’s enough to have caused me to lose drive gears completely. Next is the valve body. When disassembling, one of the valves were pretty difficult to get out. Took quite a bit of turning and pulling when all the others slid out easily. I took a picture with the valve sticking out of the slot that was being a pain. Maybe this was the issue? I appreciate any and all input. Simply asking opinions on what could’ve been the culprit for no drive gears.

Where's the forward clutch pack? Dont see it in any of the pics above - what kind of shape is it in?

How are the lip sealing surfaces on the forward clutch piston? Are they hardened, torn, etc?

Direct clutch looks smoked but could be the lighting making it look worse than it is. Intermediate and Low Rev clutch look to have normal wear to some stress.

Is the low roller clutch intact?

 

[Davidj]

Oh! I was assuming the smoked one was the forward pack. I’ll do some more looking around and check a diagram to see where I should be looking. Very new to all this. Bear with me. XD

 

[Davidj]

Uhmmm… spose this explains it. Was a long night when I got to tearing this apart and I guess I just tossed this aside. Wow. I’m assuming there shouldn’t be roughly 3/8” in between there?

 

[NickTransmissions]

Oh! I was assuming the smoked one was the forward pack. I’ll do some more looking around and check a diagram to see where I should be looking. Very new to all this. Bear with me. XD

Maybe it was - you should have four clutch packs on the bench but I only see three so post a picture of the one not already shown and we will go from there.

do you have the ATSG Manual for these transmissions? If not, that should be your very next move - DO NOT rebuild any auto trans without the manual for that unit handy! You'll find all the diagrams you need along with correct nomenclature for all of the parts...If we're to go back and forth in the thread, we all want to be speaking the same language using the correct terminology, part designations, etc.

You can purchase the ATSG manual on their website and download it once you submitted your payment. You can also look around to see if there's a free PDF version that someone uploaded to a file sharing site...I have several ATSG PDF files that I downloaded off the net for nothing...

 

[NickTransmissions]

Uhmmm… spose this explains it. Was a long night when I got to tearing this apart and I guess I just tossed this aside. Wow. I’m assuming there shouldn’t be roughly 3/8” in between there?

Yup! Now you need to find out why that clutch pack burned...Otherwise, you may repeat history w/it...The Direct clutch burns frequently but the forward clutch is always on unless you're not in a forward range position so it's not often burnt on failed TH350s...Check the lip sealing surfaces and let us know if they're hardened, torn, etc on the forward clutch piston/drum. See post #7 for my other responses...

 

[Davidj]

Yup! Now you need to find out why that clutch pack burned...Otherwise, you may repeat history w/it...The Direct clutch burns frequently but the forward clutch is always on unless you're not in a forward range position so it's not often burnt on failed TH350s...Check the lip sealing surfaces and let us know if they're hardened, torn, etc on the forward clutch piston/drum. See post #7 for my other responses...

Took a few pictures of what I THINK may be the parts you’re asking about. Please let me know if I’m barking up the wrong tree again. One is of the piston. And one I believe is the center support and the low roller clutch? The seals on the piston do still seem rubbery and not hardened or torn across. One small bit is missing just a tiny bit off the rim. I’ll try to take another picture showing that.

 

[Davidj]

I’ll be getting that manual the minute I sit at the pc! Thank you!

 

[NickTransmissions]

Took a few pictures of what I THINK may be the parts you’re asking about. Please let me know if I’m barking up the wrong tree again. One is of the piston. And one I believe is the center support and the low roller clutch? The seals on the piston do still seem rubbery and not hardened or torn across. One small bit is missing just a tiny bit off the rim. I’ll try to take another picture showing that.

That second pic does appear to show a cut forward piston lip seal. yea, take another picture but even a small laceration is sufficient to cause the damage sustained by that forward clutch. Also check the underside of the forward clutch pressure plate and see if there are no little indexing marks, one mark or two marks...That pressure plate is selective, meaning there's multiple versions of the same plate...if your clearance is not within spec (i.e. too loose or too tight) you may need to swap that plate for a different version to get your clearance...My video series on the transmissions discuss this among many other things.

Here's the playlist to help you prepare for the rebuild, in case you haven't seen it yet:

TH350

Share your videos with friends, family, and the world

www.youtube.com

 

[Davidj]

Here’s the forward drum after a little cleaning. There’s a gouge I’m not sure I should be concerned with. The rest looks great considering how the clutches look. Also a possible better angle on the piston and would this be the indexing mark on the pressure plate? I’ll be binging your series tonight sir!! And likely as I rebuild XD

 

[Davidj]

At least now I know there’s something here. Those first clutches didn’t seem so concerning but WOW these are bare bones. Thank you for pointing me in the right direction. Was worried I’d get this all torn apart and not find anything wrong to find out it was an issue in the steering column or something

 

[Davidj]

That second pic does appear to show a cut forward piston lip seal. yea, take another picture but even a small laceration is sufficient to cause the damage sustained by that forward clutch. Also check the underside of the forward clutch pressure plate and see if there are no little indexing marks, one mark or two marks...That pressure plate is selective, meaning there's multiple versions of the same plate...if your clearance is not within spec (i.e. too loose or too tight) you may need to swap that plate for a different version to get your clearance...My video series on the transmissions discuss this among many other things.

Here's the playlist to help you prepare for the rebuild, in case you haven't seen it yet:

TH350

Share your videos with friends, family, and the world

www.youtube.com

i've sttarted with your 2 hour teardown and inspection video. one thing of note so far, the governor cover did not have the wire bracket that holds it in place. the cover was still bottomed out to the case though and very secure. no dents, but i did find it odd when i saw the holes for this wire bracket to go in, but no wire.