Muncie leaking worse than ever

Hello again. For people who replied to my last post I want to start with thanks for everyone being so quick to try and help.

I ended up trying to replace all the seals. Front bearing retainer, the shifter shafts, etc. I used very light amounts of anaerobic gasket maker around the seals because that’s what the Muncie tapes guy said he used. It now leaks very very bad. So most likely something I messed with.

I came back to it after letting it sit for maybe a week and the puddle under the transmission was huge instead of the normal tiny puddle. My question is should I just give up with this transmission? I have enough for a tkx 5 speed and the swap kit. I know that’s insanely overkill for a stock 350 but I’m also tired of this transmission causing me so much grief.

The other option I’m thinking about it have a professional shop rebuild it if I can find one that’s willing to work on one that old. I’m not really willing to try again myself because I’m scared of just breaking it even more and then finding out later it won’t hold oil, again.

I really really want this car to work so I have a reason to not get rid of it. Thanks for any thoughts.

Edit: if it matters I also found that transmission is most likely from a 1965 chevelle. Probably but not 100%

Can you tell where the leak is from? I don’t think I’d give up on it unless the shafts seemed to have a lot of play and were ruining the seals. Might price rebuilds vs the 5 speed and whatever else might be needed for the swap (new driveshaft, adapter, trans mount relocation, etc). If the car isn’t stock, you might just rather have the 5 speed, with OD, though…,

No experience with that transmission myself, but it is a common topic in hot rod magazines. Maybe you can get some tips here

I’m guessing you just don’t know all the tricks to get it to stop leaking is all. Suggest to not yield to defeat quite so soon.

I can’t tell and didn’t look that hard because a friend is borrowing my jack but it looks like the biggest area of the leak is under the front

Have you considered the possibility of a cracked case?

You aren’t storing this with the tailshaft low, are you? The oil will run right out the output ahaft end if there is no driveshaft yoke or a plug in it.


I took it that the trans was completely installed back in the car and ready to go with everything bolted up, but maybe not.

It’s all bolted up. I’ve driven it once and it was leaking but it was leaking about the same amount as before. Then once I left it for the week it puked.

All back together to the best of my ability

Just a few possibilities. Looks like you need to check some things.
Wrong seal somewhere.
Worn sealing surface on shafts.
Worn bearing causing shafts to wobble.
Poor installation.


Some food for thought but since you say the leak is up front I assume that means at the bell housing juncture.
Any chance that is not transmission oil leaking and that it may be motor oil getting past a rear main seal?

Speaking for myself, any time an engine or trans is out for whatever reason the rear main seals, converter seals, manual trans seals if possible, get replaced.

Another lesser possibility is a worn pilot bushing which might allow the trans mainshaft to flop around a bit and beat up a new mainshaft seal.


If this is your ‘87 Firebird have you checked with your local auto-recycler (or what ever the current term for junkyard is) about finding a replacement transmission, and associated parts, for that generation Camaro/Firebird?

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I thought he had a 1st gen Firebird, a '68. A Muncie, a Borg Warner T10 or a Saginaw would be appropriate…

But a Tremec Tkx would be a nice choice.

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Probably a bad install. The fact it was leaking decently bad before is just making me wonder if it’s worth trying to save. And to mustangman and purebred it is a 1968 first gen. The motor is an 87 sbc

He did not state in this post the year. In a different thread the OP asked about installing a rev limiter on his ‘87 Firebird, hence my question.

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Checking his threads,
Looks like it’s a 68 Firebird, 87 Chevy engine, 65 Muncie transmission

As a first generation FB, would cost much more, but I would be looking for a Pontiac 389, or larger (for some unknown reason, I like the 421) engine&transmission. For looks, with tri-power intake. But I am a dreamer.

67 up FBs got 400s and the tri power was dropped but the engines got big Rochester quadrajets.

I, too, would prefer to see a Pontiac engine in a Pontiac. 421s, 428s or 455s are a drop in as easily as a 400. With Edelbrock aluminum heads and manifold, the weight would be similar to a smallblock Chevy.

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Yeah it would be really cool to one day have a Pontiac engine in it. It’s just that it was the cheapest engine and since I’m just out of highschool I don’t exactly have the funds for all the fun stuff. One day though hopefully I’ll put a true Pontiac engine in it.
And it_s-me is dead on. At least I’m 90% sure on the transmission

I would suggest that you do not get discouraged and throw in the towel on it. I will reiterate; have you made sure that leak is gear oil and not engine oil from a leaking engine rear main seal? They do have different smells and the viscosity is far different.

Neat car so hang onto it. Friend back in the day had a 68 Firebird with 400/speed/Posi rear axle. That car was a beast.
I was with him one night when a guy pulled up and wanted to run them. The other guy was driving a Mercury Cyclone GT with 428, dual 4s, etc.
My friend whomped that guy so bad in a quarter it was downright embarassing.

The other driver (an off duty OHP trooper of all things) was beyond livid. He jumped out cursing and making excuses. “My throttle linkage is messing up…”.
Friend just said; “I know what you mean. The linkage on my QJ is messed up also. I don’t think the secondaries are opening”. That really set the guy off.

That is funny!

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