th 350 tranny leaks no matter what

[big red money p]

So here is the problem, stock pan was too small so went with an aftermarket deep pan(chrome) leaks after proper torque patternwas done. Now I thought ok I would get a deep aluminum, with all flat mating surfaces, new gasket(thick cork) torqued to specs, still leaks. I know sealer is a no no so what do i do next?

[TT Boy]

try getting rid of the cork completely and use just black RTV silicone. make extra sure the mating surfaces are completely clean before you start.

[campaug86]

spend the big bucks on a rubber gasket with torque washers inside it so you cant squish it. also check your seals.

[bwright]

spend the big bucks on a rubber gasket with torque washers inside it so you cant squish it. also check your seals.

That's what worked for my leaky TH350.

[NovaMan]

Permatex Ultra Black should work - it's formulated for great oil resistance. I've never tried RTV alone, but I have had good results from coating the gaskets. Also, the rubber gasket with torque-limiters should work nicely.

Now if only I could get my TH350 to stop leaking where the dipstick tube goes in. :banghead:

[Bigdrumma22]

My trans has been leaking too for at least the last 2 1/2 years I've owned it. Is this a common TH-350 problem? Changed the pan gasket and fluid when I got it with RTV and black rubber gasket that came in the kit, but it still leaks from somewhere. We thought the new gasket would fix it, but it didn't. Possible crack in the case? Don't mean to hijack, but mines got issues too.

[NovaMan]

Have you checked the trans cooler lines/fittings and where the dipstick tube goes into the case?

[diehrd]

Also check the servo on the passenger side as they leak and make it look like a pan leak, so does the dip stick tube,

The guy with the dip stick tube make sure there s not a hair line crack in the tube it self , then get the boot seal that replaced the o-ring seal from a local tranny shop and toss it on.

When I had the Tranny shop we always used cork on out pan's as my mechanics just preferred them and we never had any sealing issues. Check to be sure the pan surface is level there are times we had to straighten the flanges.

The biggest mistake in a pan gasket install usually is the bolts are put on to tight,the fasteners correct tightness is snug plus 1 turn if I remember correctly.And why my guys preferred cork is they where able to see gasket compression and knew when enough was enough.

[NovaMan]

The guy with the dip stick tube make sure there s not a hair line crack in the tube it self , then get the boot seal that replaced the o-ring seal from a local tranny shop and toss it on. Please tell me about the boot seal.

[diehrd]

Please tell me about the boot seal.


Tell ya about it ?

Call a tranny shop ask for a dip stick seal that looks like a top hat not an o-ring :)

[Bigdrumma22]

Have you checked the trans cooler lines/fittings and where the dipstick tube goes into the case?
I'm pretty sure it's not the cooler lines as I replaced them not too long ago, had problems at first, but then got them aligned right with no leaks. Problem was existing when we bought the truck, but I hadn't thought of the dipstick seal... might have to check that this weekend. Where is the servo... by the modulator? Pic if you can. Thanks.

[NovaMan]

The servo is on the passenger side of the trans just above the pan rail. There will be a round, semi-bulbous cover on it held on with a bail. If you take it off, be careful because some ATF will spill out.

http://www.tciauto.com/Products/GM/Hydramatic/311000.gif

[Bigdrumma22]

The servo is on the passenger side of the trans just above the pan rail. There will be a round, semi-bulbous cover on it held on with a bail. If you take it off, be careful because some ATF will spill out.

http://www.tciauto.com/Products/GM/Hydramatic/311000.gif
That's the black spot right?

[NovaMan]

Yes.