Looking For "Truck Church" On Tranny (Transmission)

[magwakeenercew2jh]

I thought I had the leaks stopped.

Long sad story shortened: TH350 was part of the pile of parts I got from an honorable pal three years ago. He told me the trans shifted nicely but leaked.

So, I took it to a guy...new seals front and back, best pan gasket, new aluminum pan. Had a one piece drive shaft built, new cross member installed. Put the TH350 in early in the build.
When I filled it up to six of the 12 or whatever quarts, one came out on the floor. Because I'm dumb and forgot to put the drive shaft in first, it leaked the last quart out before I could stop!
Put the drive shaft in (Duh!). It leaked!

I thought it was coming from the shift shaft. New tool...new dime-sized gasket. Leaked.

Pulled the trans and took it to a local shop of good repute. He showed me something inside the bell housing and replaced a bushing or something. $85.

Filled it (to about three quarts low, I think) and no leaking. But we hadn't started the motor. Finally, after a few other leaks of coolant and replacing the freeze plugs
(Yup, pulled the motor again to do it), we started her up. No tranny leaks.

When I put the following three quarts of trans fluid in and drove 1/4 mile to the trucks new resting spot, leaks! Looking on the dipstick (while the truck was running, of course),
I couldn't see "red", altho it seemed "wet" up past full.

I had a Lokar-style braided stainless dipstick that was suspect because it was frayed on the trans end, altho the o-ring in the business part that went into the trans looked to be uncompromised.
So....I bought (a good one, I think) an aftermarket dipstick/filler. Leaked...from somewhere.... in seemingly the area of the dipstick/filler area (pass side above the pan/gasket/casting, in front of that big circular thing...
...and seemingly, behind where the trans cooler lines and kick-down cable are attached). The cooler lines are dry as a bone, as is the big round thing (I don't know what thios is..."regulator"?)...even down low.

So, after spending two days under the truck. Jacking it up, cleaning it off, going for a drive, jacking it upo. Looking with lights, cleaning, feeling, using a mirror, etc. I drained a quart off of what I was already worried
was not enough fluid, and there was less leaking.

Took it for a ride, no leaks.

That was yesterday. Tonight, I looked under her. Leaking.

First thing I did was come in and look on Craigslist for a 700r4. Then, after some sticker-shock, I looked for a "new" TH350...Then, I realized I was just too pissed to make a decent decision.

Here's the deal: I've sunk so much dough in this truck...I want it to be right...and I'd like to get some gas mileage....but a 700 is a lot of gas money....but if it wouldn't leak.....
And if it would fit in direct place of the TH350???? I don't know. New cross member? Re-do the drive shaft? I'm running 3:08's non-posi behind a very mild 350. Already have a bunch of dough
in the driveshaft and ....waah, wah, wah, waaaaah.......

When I get like this, I like to go to "Truck Church"....So, here I am. I'll take all suggestions. Please...

What would you all do?

[shawno72]

Rebuilt th350 should retail for around $650 and will bolt directly in. 700 will require driveshaft work and more $$$. I've been going back and forth as to which one to get. Right now I have the ole four on the floor and I just installed a 3.08 posi. I'm thinking th350 cause I can get a nicely rebuilt with warranty for about $400. I have modify the driveshaft with either trans. I really only want to take my truck to LA twice a year so the gas spent will still be less than the extra cost of the 700. And I can still roll at 70-75 no problem
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[magwakeenercew2jh]

If I pull her into the garage (on the gravel driveway right now), let her cool down, and it seems that the leak is coming from that dipstick area.....And then ff I pull the "new" dipstick, holder and all, out of the casting body and trans fluid gushes out of that hole,
does that mean the tranny's over filled?

Maybe with the (really nice) aftermarket finned aluminum pan the reading on both dipstick/filler is wrong....I just can't remember over all the $200 worth of fluid how many quarts are in there(an over-statement for drama! But not too much) .

I'd hate to dump a TH350 that shifts smoothly and works well other than this exasperating leak... for another TH350... for that kind of dough. I suppose if it came to that, I'd pull it out and take it in again. I'm just trying to make it right without
pulling it if I can. But if I pull it...then all bets have to be either off...or reconsidered. 'Cause if I pull it and have it "fixed", put it in and it leaks again, then I hope some of you would, from time-to-time give my wife a ride up to
The State Mental Asylum For The 67-72 Insane.

[chopped68]

the turbo 350 with converter will be about 10 quarts with the stock pan,deep aluminum pan 12 quarts.if it is overfilled,it is coming out of the vent in in the top of the case.also check the dipstick tube rubber grommet and the orings on the vacuum modulator(it is at the passenger side rear just above the pan).1 thing you could do for your t350 is get a low first gear kit.it is a 2.75-1 first gear so you could run a taller axle ratio.

[magwakeenercew2jh]

Originally Posted by chopped68

the turbo 350 with converter will be about 10 quarts with the stock pan,deep aluminum pan 12 quarts.if it is overfilled,it is coming out of the vent in in the top of the case.also check the dipstick tube rubber grommet and the orings on the vacuum modulator(it is at the passenger side rear just above the pan).1 thing you could do for your t350 is get a low first gear kit.it is a 2.75-1 first gear so you could run a taller axle ratio.

Thanks much for all of that. Where's the vent in the top of the case?

[chopped68]

the vent is on top above the transmission cooler fittings.

[BruthaMan]

I feel for you, am kind of going through the same thing. Trying to get the truck to a point where I don't have to put a maxipad down on the driveway every time I park the truck.

Transmission is finally sealed up. Did basically what you did, took the pan out, cleaned everything down, replaced filter, put on a new "top of the line" gasket (used gasket sealer), then replaced the seal on the shift link. Added in some Lucas transmission "conditioner" that has sealer as well. So far, not leaking.

Motor (GM crate with about 12k miles) had a small leak from front seal. Last oil change (mobil 1), added some motor leak stuff. So far, doing good.

Went out the other day and there was a big leak under the truck and about had heart failure. I knew it wasn't trans because of the clear color. Started checking around motor and oil pan, but nothing. Started thinking maybe someone came along and just dumped a cup of oil under my truck to mess with me!

Then as I was sliding out from front, I saw some moisture. It was the power steering box. I had loosened it and moved it when replacing belts last weekend. The hose going into the pump looks old and cracked. I tightened it down some, but plan to replace it when I have some free time.

Have you tried any transmission leak products? The Lucas product worked pretty well for me. Maybe it would be enough to stop the leaking for a while, and provide the opportunity to save up for the new transmission.

[SS Tim]

The trick I was taught years ago is if you don't know how much or if you suspected an overfill was to loosen the pan bolts with the vehicle running and hot, let it drain. When it stops it should be real close to the normal running fill level. Tighten everything up and clean. Also TH350 did have case porosity problems, how old is it? The dealers used to epoxy the outside of the cases. Had a bulletin at one time but.... its somewhere 'round here.
Now do you have a really big external cooler that might be draining back causing enough of an overfill to come out of the vent? You can always try a check valve in the cooler supply line or lowering the cooler.

[LockDoc]

-
If fluid is coming out of the fill tube hole in the case it has to be over full. If you can't trust your dipstick reading do what Tim suggested to get you in the ballpark. The only thing I'm not sure about is having it running when you do it. I can understand having it hot so the fluid is expanded. I am by no means an ATM guru, so I don't know.

If you decide to go with a 700r4 the 3.07 rear gear will be to high. It can cause the trans to overheat when it is in overdrive and blow fluid out of the front seal, and your mileage will actually go down. I just went through this with the Suburban... I'm changing over to a 3.73 rear gear in it.

LockDoc

[SS Tim]

Originally Posted by LockDoc

-...do what Tim suggested to get you in the ballpark. The only thing I'm not sure about is having it running when you do it. I can understand having it hot so the fluid is expanded...
LockDoc

The reason you have it hot and running is that trans fluid expands and that raises the fluid level over cold. The other is that an automatic transmission has a fair amount of fluid in action when the trans is spinning. The valve and lubrication passages, clutch packs and the torque converter all take from the pan during operation and drain back when the engine is off. Next time you are checking trans. fluid look at it cold engine off first then start it and run it there will be a noticable drop in level even with the fluid expansion.

[LockDoc]

Originally Posted by SS Tim

The reason you have it hot and running is that trans fluid expands and that raises the fluid level over cold. The other is that an automatic transmission has a fair amount of fluid in action when the trans is spinning. The valve and lubrication passages, clutch packs and the torque converter all take from the pan during operation and drain back when the engine is off. Next time you are checking trans. fluid look at it cold engine off first then start it and run it there will be a noticable drop in level even with the fluid expansion.

Thanks for the explanation. I didn't think about the pump sucking it out of the pan.

LockDoc