TH400 Leaking

[Steve70Carlo]

Hey guys,

 

my TH400 wont stop leaking around the pan. I replaced the gasket twice and last time went with a quite expensive, Moroso blue, steel core gasket that is guaranteed not to leak. It's only leaking from the front "driver's side" corner of the pan, but it's still leaking and enough to make a mess out of the garage floor. Is there any way to stop this leak without silicone? I thought I have seen some sort of metal bracing that you can buy that you bolt to the corners that helps seal the gasket better.

 

Any help would be appreciated!

 

Steve

[bobsmc]

are you sure it coming from the pan?

often times the leak starts above and follows the pan in the area of the leak.

check the selector shaft seal.[shifter shaft]

[CrazyDavey]

what Bob said....400's are leaky sob's...also if it's too full when it gets hot it can come out of the vent on top of the case and run down the sides....

[Steve70Carlo]

Thanks Guys,

 

I'll check that tonight after I get home and let you know what I find.

 

 

Steve

[Sam (Bones)]

if the pan has been over-tightened and distorted the flange (gasket surface) it will leak

[geartech]

I just had this happen to me (replaced the gasket twice) in a Lemans I have with a TH400. It turned out to be the dipstick tube O-ring, not the pan gasket after all, although it looked like it to me at first. Also the modulator is right there too.

[Steve70Carlo]

So I haven't been able to locate the leak yet but thought I would ask what you guys thought about another idea involving the TH400 in my Monte.

 

I currently have a full manual valve body and a 3200 stall converter. When I originally built the car, I built it for drag racing purposes but kept the stock look.

 

After 12 years of the car being done, I want it to be more driver- friendly and to be able to cruise more with it.

 

Do you guys think I could just order a lower more street- friendly stall converter? Or do you think I should have the trans rebuilt and gone through totally?

 

I have had no issues and the manual valve body doesn't really bother me but I wasn't sure if I could put a lower stall converter in it or if I would need to have the entire trans redone.

 

I also currently run a 4:10 gear ratio in the rear and am switching out to a 3:73 ratio.

 

As a final note, I am not gifted in the areas of setting up rears or rebuilding transmissions. I could drop the trans and change the stall converter myself, but if the trans needs to be rebuilt, then that's something that I would have someone else do who knows their way around the inside of those things. I'm in Maryland, so, if any of you know who to point me to, that would be great.

 

As always, your input is greatly appreciated!

Thanks!

 

Steve

 

[Will]

If your willing to spend some time doing the research I did my first rebuild last summer. I got the B&m rebuild kit because it has the best instructions with detailed pictures of every step. Ron Sessions "How to work with and modify the Turbo 400 transmission" helped immensely as well (as was loaned to me by a fellow club member). But its a bit hard to come by these days. I layed out some moving blankets on the floor and went step by step in order. In the end she went back together and runs great. PLus I get to say I rebuilt it myself. Worst case scenario your out 170 for the experience.

[geartech]

Was anything unusual done when it was built, besides the manual VB and stall converter?

Generally speaking, its not a problem to change the converter without rebuilding it... as well as change the valve body back to a stock one, some other aftermarket one, or rework what was done to make that one manual. If the trans is generally working ok (no slipping, etc), you should be able to just change the valve body to a street/strip automatic one, or a stock one. If you buy a new one, I'd follow their instructions on the check balls to have in place and use the valve body plate supplied with the new valve body.