350 TH pump lip seals - internal

[dennislbrooks]

My 350TH ( not presently in any vehicle) developed a cold start delay when putting in reverse or drive. Fluid level is fine, My research indicates it is the lip seals in the pump. Has anyone replaced just these 2 internal lip seals and did it cure the problem? My trans otherwise shifts and works fine.

[kwmech]

There are no "lip" seals in the pump. You have a gasket (case to pump) you have a square cut "O" ring around the outside, and you have the seal for the torque convertor. None of which have anything to do with a slow reverse engagement. If anything it will be the lip seals on the reverse drum in the bottom of the case, in which case the whole thing has to come apart and you may as well get a soft seal kit and do them all

[Bigdav160]

Does this only happen on a cold start? Perhaps only once a day? Then the seals are hard and it's time for a rebuild.

[dennislbrooks]

Yes cold start, perhaps once a day.

And I did find the 2 lip seals in the pump. I am not so sure that when the trans shop in Dallas rebuilt the 350, they just did not pull the pump apart to change the lip seals. Kinda a lazy overhaul back in 2003.

I do know that when I pulled it for a Monster 700R4, once it warmed up it found the gear and ran and shifted fine for the day.

You can see both lip seals on the intermediate apply piston in the pump.

I know other people that have had this situation on an otherwise fine running 350TH trans.

[clinebarger]

That's the Intermediate Clutch Piston, Wouldn't cause a slow engagement issue.

Half of the TH350 cores I take in are JUNK & hard part prices have skyrocketed!

[dennislbrooks]

Hmm, I guess I misunderstood Cliff Ruggles on his troubleshooting.

So then the problem is not the pump but the seals on the low/reverse apply piston which has 3 square cut seals near the tail end of the transmission?

[kwmech]

More than likely, they can get hard and cause the issue you are speaking of. Nice to see you back Cline

[cadillac_al]

My K20 has been doing that for about 8 years. I just wait 5-10 seconds and it's fine the rest of the day. I suppose it will need a rebuild someday.

[clinebarger]

Originally Posted by dennislbrooks

Hmm, I guess I misunderstood Cliff Ruggles on his troubleshooting.

So then the problem is not the pump but the seals on the low/reverse apply piston which has 3 square cut seals near the tail end of the transmission?

That wouldn't explain the delay in drive (D3), The Lo/Reverse Clutch is not "ON" in D3-First Gear. The only clutch that come "ON" is the Forward Clutch.
The Lo Roller Clutch holds the rear carrier.

Reverse relies on 2 Clutches.....The Lo/Reverse Clutch to hold the rear carrier & the Direct Clutch to drive the Sun Shell via the Forward Clutch Drum.

This could be a converter drain-back issue caused by worn Stator Support Bushings. Even in conjunction with hardened lip seals.....

[dennislbrooks]

Now we are talking.

The 2 lower bushings in the stator were somewhat grooved. The top not so bad. Input shaft looks fine. I have replaced all 3 bushings in the stator and test fitted it on the input shaft. And replaced the torque converter bushing and seal.

The torque converter was purchased new and I believe is a summit model -- been too long.

I am awaiting the lip seals for the intermediate apply piston. Pan fluid was clean. I still believe the trans was actually overhauled but not the pump.

I probably got what I paid for. Trying to make it better so I can use it in front of a NP208. It has been in front of one before.

The trans did not have this problem the first 12-14 years and has not been abused since I got it.

Old removed bushings then new bushings in stator.

[raceman6135]

Originally Posted by kwmech

Nice to see you back Cline

I second that! Cline's knowledge, and the ability to relay that to us 'common folk' has always been appreciated by many.

[clinebarger]

Didn't realize your're rebuilding it......Replace all the lip seals & the square cut seals on the Lo/Reverse Piston!

How's the case lugs where the Center Support rides?

[dennislbrooks]

This is the first time I have ever tried a rebuild on an automatic so it will be a somewhat slow process for me. I do have a Cliff Ruggles manual for reference. I will examine the case lugs.

Just a side note on another thread I saw. I do have a Monster 700R4 with lockup (3 years) with a np208 in my 67 behind a 402 BBC and have not had a problem with it. It does have a hard shift to second unless you come more off idle. I am not plugging any vendor but just sharing info. I also have a Raptor 700R4 without lockup (3 years) behind a 455 in my 70 Olds 442 and have not had any problems with it. I think they are out of business. The first second shift is smoother than the Monster but I figure that the shift kits differ.

Clinebarger, if I still lived in Flower Mound and if you are still in business, I would bring it over. My 67 came from Keller.

The brooks 350TH with np208 will be behind a 250 inline 6 and may be the worst of the lot. 8-)

OK, I need direction on removing the only snap ring I think I see for the planetary housing. It looks like the snap ring is near the top of the output shaft spline. Please show me the tool or tell me the method.

OK made it past the snap ring. Case support lugs show no damage, look like original casting unless you guys see something. Next I need to make a spring compressor tool for the low/reverse piston.

[kwmech]

Tool I have for that includes a 1/2'' bolt about 7-8'' long with a wing nut, a large plate that covers the bottom of the trans with said 1/2 hole centered and an internal piece that pushes the spring assy down to access the snap ring with either a pick or snap ring pliers. Replace that bushing also and stake it down so it doesn't walk in the case. Lugs in the case do not look too bad for wear

[dennislbrooks]

Ok, I got the last snap ring out and am down to just the low/reverse apply piston which Cliff Ruggles says to just lift out. Hmmmm, with 3 o-rings on it it does not just want to just lift out. I have found little to grab hold of to get it out.

I am still pondering.

Also...... I did not find what Cliff Ruggles calls a RETAINER SPRING supposedly near the center support assembly. I did not hear anything hit the floor. But will look some more. I do not think it was in it. It looks like 1/8" wire of sorts.

I did find the Retainer slug. It looks similar but different than the manual.

OK, missed a step on the low/reverse apply drum removal- it takes air pressure - case is now empty.

[clinebarger]

The case looks pretty good far as TH350 cases go (It does have a little wear). It also has a "Case Saver" installed in place of the factory "Anti- Clunk" Spring.

I usually recommend/install a 4L60/4L60E Center Support that utilizes a wider Roller Clutch, But you MUST watch the Lo/Reverse Clutch Clearance. I like .080" to .095"

I also like to use Late 4L60E/4L65E (Turbulated) Lo/Reverse Steels.......Here's some selectable thicknesses available from Raybestos..........
*.047" thick Part# 511594
*.069" thick Part# 511589
*.089" thick Part# 511591

The TH350 uses .099" thick Lo/Reverse Frictions & the 700R4/4L60/4L60E uses .087" thick Lo/Reverse Frictions......Either friction can be used to set the desired clearance.
Yes.....You can mix them together in the same stack!

[dennislbrooks]

Ok, I see a lot of choices on ebay. If I go the 4L60E parts route -- leaning that direction - you may see this thread pop up occasionally with a question. I need to educate myself on measuring these clearances and procuring the correct alternative parts.

Thanks all for you help.

[dennislbrooks]

Just a follow up. I have the rebuilt 350TH in the 59 GMC 4wd. A 250 I6 is in front of it with a NP208 behind it. Coolant lines, vacuum, and kickdown are all hooked up.

The trans seems to work fine with no hesitation on cold start. Firm shifts thru all gears and reverse works fine. Downshifts fine. No weird noises.

It held about 10 quarts or so. No apparent trans leaks. Transfer case has a slight leak.

[Bigdav160]

Where's my thumb's up icon? Good job.

[AussieinNC]

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