TH350 fluid leaks

[Kliegl]

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[montefrazer]

Several other things to check are the vacuum modulater, left rear of trans with hose connected to it, drain plug if you have one, and pan gasket. These leaks are hard to find since air movement under the car forces the fluid toward the back of the car while driving. When you stop, it drips from where it ended up. I just replaced the O ring on the dip stick tube on a Turbo 350. It leaked there and ran down the case to the pan and dripped off the back of the pan. You may have to get under the car and clean off the trans and then follow the fresh wet areas to their source. Good luck.

[superstk]

Remove the cover from the front of the tranny and check if it's not from your front seal. That one is a PITA to do. Have to remove the tranny to replace it.

 

Fred

[Kliegl]

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[Guest]

I am leaking ATF as well;

it seems like it gathers around the bottom pan

but it seem to come from the front. Could it be the front seal? Could it be the pan gasket? I have access to a hoist, will it still be a ruff job to do the front gasket seal?

[stangeba]

Just to put one more thought out there, my 71 THM350 started to leak a bit after hitting 90,000+ miles, no big deal BUT!

Pulled it at 114,000 for a reseal, still leaked

pulled it and resealed again plus a new ft pump, still leaked.

Pulled it again and found a crack in the converter weld, replaced it and no more leak. (Over a four year span)

now at 148,000 it got a bit of a leak again plus the ft engine seal and rear main seal a bit also. (Cardboard on the floor)

 

Bruce

[wallaby]

Get it clened up under there and find where the leak really comes from. You'd be surprised how far the fluid will travel from the source. I had a bad seal in my steering box, and I swear everything under the car had fluid dripping from it EXCEPT the steering box...even the floorboards and trans were wet.

So step one is to clean up the mess as best you can and then try to find where the oil comes from. Sometimes the fluid is hard to spot when it's seeping out onto clean aluminum; I dust the suspected area with baby powder and any fluid shows up pretty good.

[Mo's70MCs]

Let's not forget the xmsn lines, those should be checked closely as well! i.e. loose fittings, but I'll agree a worn torque convertor, where the seal does not seat well (worn groove in it) will allow fld seepage and or crack in it.

 

Rod

 

[Big Jim]

I had mine rebuilt by what I thought was a good shop because it was leaking.

I didn't know if it had been rebuilt before. I still have leaks.

One is at the tailshaft and I think the other is at the speedo gear. It was supposedly replaced later by the same shop. A few months later that shop was closed. There goes my warranty.

It cost over $600.00 to rebuild.

It's a good thing it's not a daily driver.

I gues we live and learn.

[Bob Hansen]

One common item is that the driveshaft yoke can get wore down and gouged and will still leak with a new seal.

Overfilling the trans will cause fluid to come out the vent on top of the case when the fluid heats up and expands.

 

Remember a 1st Gen Monte does not leak!, It is just marking it's territory!

[kc8oye]

check the dipstick and kickdown cables.

 

there are two different designs for seals for these.. early designs (pre 82 i think) used o-rings.. late designs used lip seals.

 

they are not compatible.

 

if you have an 80-somthing TH.. and someone put 70-somthing parts in it.. anything is possible.

 

I make a 72 kick down fit my '89 case with a healthy glob of RTV

[Big Jim]

I was talking to a fellow Monte owner at the cruise in at Hardee's in Stanley NC.

He has the same persistent problem on a Nova with the TH350 Tranny.

The speedometer hookup leaks.

I have had the transmission rebuilt.

Put new speedo gear & O ring and it still leaks.

When I took it back the transmission guy, He apparently put silicone in there to stop the leak.

It didn't work.

Another mechanic took it out, cleaned out the silicone and stretched the O ring.

It still leaks.

He said the next thing to do is to change the speedo gear case.

The fellow Monte owner said he changed case on Nova and still leaks.

Is there a miracle cure out there?

We would both appreciatte the magical cure.

[Kliegl]

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[Big Jim]

I have one of those metal drip pans (WalMart Special) on the floor and it usually catches any drips. Oil or Transmission Fluid. Just have to clean it every so often.

[Guest]

big jim

i had the same problem with my speedo gear. repaced the gear, a couple of o rings and yes somebody got me with the silicon, but then i replaced the "bullet" that holds the gear and used the o ring it came with (went to local gm parts counter, in stock)and haven't lost a drop since. the gear actually worn the bullet over the years so it was leaking not the o ring.

[Big Jim]

Did you get a new bullett or a used one and where did you get it?

[Big Jim]

Well I got One on Ebay. It's a new steel one. Hope it does the trick. the seller said it will work. I guess we will see.

[motoradot]

Mine is doing the same thing, leaking at the bullet on the tailhousing.My driven gear even had wear like a harmonic ballencer get where the seal rides on the gear...Replaced the gear and seals and it was a tighter fit but when you would move the speedo cable you could still see that it wasnt a tight fit. I have a parts tranny and the bullet is tight on it,so it looks like I,m gonna have to try it.It loooked a little different so I may have to change the tailhousing too

[Big Jim]

Check it out.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1,1&item=7998774742&sspagename=STRK%3AMEWN%3AIT

 

This is what I ordered on Ebay. I should get it tomorrow. Keep your fingers crossed and maybe this will do the trick.

Jim

[Big Jim]

Hi Guys,

I'm almost embarresed to tell it but I got the Speedo housing in. Jacked up the car, Took out the old housing. I tried to put the gear back in and somehow pushed it to the left into the case and can't reach it now. The Speedo Housing fits good though. I did not realize you have to put the gear into the speedo housing. It was in plain sight until I tried to fit it back into the transmission. Dumb Dumb Dumb.

 

What am I going to have to do to retrieve the speedo gear from the case?

Take it to the transmission shop?

Will it be safe to drive with the gear loose in there?

[kc8oye]

hrrm, I'm going to have to explore this.. I'm certain it's my speedo cable or the housing, or somthing related to the speedo leaking, I can't get in there with channel locks to do the cable up (using a 60-somthing impala crossmember in the monte for a bolt-in mount) and it's definately leaking there. perhaps next time I have access to a hoist I'll pull the whole unit and just clean/inspect it and see what comes of it.

 

btw.. if you need to.. just pull the 4 bolts out holding the tail housing on.. whole thing should slide off then, and give you access to your part.

[Big Jim]

I talked to a guy at the transmission shop and he said when he rebuilds a turbo 350 he never reuses the speedo bullett. he always replaces it. Said the aluminum bullett is a piece of crap. He also said you can get it at a transmissoin parts store for about $4.00.

[Big Jim]

I am Leak Free except for gas tank lines.