transmission leak

by pila Fri Apr 10, 2015 3:10 pm

I have the TH400 ready to come out of my Elco project. It's been leaking a while, but don't really know where the leak is yet, so, out it comes.
Luckily my exhaust system is band-clamped together & no U bolts on it. Comes apart very easy, and I had to remove the down pipes to get the cross member out.
Early on, I thought the OEM steel pan was leaking at the gasket flange, but after putting a cast aluminum pan on it, it still leaks the same way.. Head Bang

Maybe I'll have it out this weekend.......

by Joe73 Fri Apr 10, 2015 4:21 pm

Id like to run the ribbed rubber one with steel center. Theyre reuseable and cant overtightened.

by thatfnthing Fri Apr 10, 2015 4:37 pm

Leaks were the bane of my existence when I had the TH350, so I feel for you.

by pila Fri Apr 10, 2015 5:55 pm

Never had any leak problems with all the TH350s I rebuilt. I thought early on that the front seal was leaking, but that is kinda high-up to leak that much fluid. I'll get a better look when it's out & on the bench.
There's some oil in the bottom cover on the flex plate also, so it's hard to pin down while the trans is in the vehicle.....

by BBMALIBU Fri Apr 10, 2015 9:38 pm

Wait, you took the trans out to find a leak?

TH400 pan gaskets are known to leak.

If the pan is leaking, try a Fel-Pro TOS18621 gasket with a very very thin coat of that brown Permatex aviation sealant.
I know you are not suppose to use sealant on the gasket, but I don't think a very very thin coat, allow to dry before adding trans fluid, will hurt the trans. I did it, no leaks, trans still works.

Also, check the selector shaft seal, very common, can look like the pan gasket is leaking.

by pila Sat Apr 11, 2015 12:22 am

Yeah, I went through all that, and went to a cast pan for a better gasket surface etc, but I know what you mean.
Thanks for that gasket part number !! And I'm not against using a skin coat of sealant ! Smile

Bill

by bracketchev1221 Mon Apr 13, 2015 6:37 am

As a test, run a hose from the vent to a soda can tied up under the car. Take it out for a good drive and see how much fluid winds up in the can. You may be blowing fluid out the vent and it running down the trans. I chased leaks all over on my race trans. Started collecting the vent gases (and fluid)and the leak stopped.

by pila Tue Apr 14, 2015 12:26 am

Well, it's ready to drop out. And the vent thing crossed my mind too Ray !! It does kinda look like fluid is coming from up top someplace. I may find out tomorrow when I have it out.

by 77mali Tue Apr 14, 2015 6:02 pm

Darn leaks! Hope you find it Bill (I'm sure you will).

Going through some leak BS too w/ my truck. I think its the end seals on the front axles. UGH...I'm gonna have to drop it to replace them & the gasket too. Not fun.

by pila Tue Apr 14, 2015 6:42 pm

Today I have it off of the engine, sitting on the trans jack. I have to raise the body more in order to get it out from under it., or maybe slide it off of the jack & slide it out from under.....that kinda sucks also...
I will have to jack the engine along with the body if I raise it...

The transmissions get heavier as I get older !! Very Happy

by bracketchev1221 Tue Apr 14, 2015 6:52 pm

Yes a t-400 sucks. They are heavy as hell. I can't get mine high enough. I get it off the jack and slide it out. You have to see me get it back on the jack under the car when I put it back in.

by chevellelaguna Tue Apr 14, 2015 8:43 pm

That's never fun... I'd rather take the motor and trans out than just the trans. Done it in the middle of winter after I fragged a torque converter on my daily driver 75 four door. That was.....well....sucky.

by pila Wed Apr 15, 2015 1:03 am

I always slid the TH350s off & on , but this one ....... Head Bang

Just have to see how it goes...

And the little vent tube is dry, and I have the converter wired to the case yet, so it didn't fall off. Wednesday I'll pull that & get a better look at the front of the case.

by pila Sat Apr 18, 2015 7:22 pm

Today my son helped me remove the converter from the trans, while it was still under the car, so I could look for the leak source.
It was just as I first suspected, the big diameter O-ring on the pump, where it sits in the case.
So, we wrestled the trans off of the trans jack & out on the floor. I have to check & see if I can move the pump forward enough to replace the O ring, without tearing into the "guts" !
Time to dig into the books .....or maybe talk to a local trans shop that sold me parts occasionally They may know...

by ant7377 Sun Apr 19, 2015 7:53 am

I have the same leak on my 73. Its not that bad, and when I pull it im just going to get it rebuilt which Im not doing anytime soon I dont think. P.i.t.a....

by pila Sun Apr 19, 2015 8:30 pm

I rebuilt this one myself, but it was the first TH400 I've done. If the leak is the only thing wrong with it, I'll be happy Very Happy

by Sponsored content

transmission leak

transmission leak

Re: transmission leak

Re: transmission leak

Re: transmission leak

Re: transmission leak

Re: transmission leak

Re: transmission leak

Re: transmission leak

Re: transmission leak

Re: transmission leak

Re: transmission leak

Re: transmission leak

Re: transmission leak

Re: transmission leak

Re: transmission leak

Re: transmission leak

Re: transmission leak