ukgeza

I have a 71 Vette with a Muncie 4 speed transmission. I would like to replace the gear oil in the transmission but the fill plug appears to be seized. Any recommendations on how to get it out? Can I use heat under the car? Should I just drop the car off at Aamco Transmission Repair?
Thanks guys!

Gale Banks 80'

What is indicating that it is seized ? The Fill Plug should be Steel and the case Aluminum so they should not seize.

restoman1

I agree that they "should not", but boy, they sure do! I just went through this on a 68 Camaro M20 a few months ago. I used heat, PB Blaster and everything else I could think of and it just wouldn't budge! I ended up snapping the head off and thought I would have to drill it out, but I gave it one last shot by welding a nut onto the plug, and after using a 3 foot breaker bar, it FINALLY came loose, but screwed up the threads in the main case. So after all that, I ended up having to take it apart, weld up the chewed up threads and drill and re-tap it. A 10 minutes oil check turned into a 2 week nightmare!

Ed

F22

Try a can of the CRC Freeze Spray and spray the heck out of it, for at least a solid thirty seconds to a minute (because of the size of the plug). We use it in the shop all the time.

F4Gary

I can't get the drain plug out of my M21. I may have to try that Freeze Off stuff!

restoman1

Freeze Off. Sure. The one thing I DIDN'T try!!! Let me know if this works guys.

Ed

bondoboy

I thought the 2 different metals touching was the reason for seizing up.

ukgeza

Thanks, I will give Freeze off a try.
Question: The drain bolt/plug on my Muncie 4 speed transmission appears to have no head. Is this broken or is that how it comes from the factory? Here is a pic of a transmission case I found on E-bay that looks exactly how the case on my car looks.

http://www.ebay.com/itm/1968-Chevy-C...97b43f&vxp=mtr

restoman1

Starting in 1970, all Muncie 4 speeds had both the fill AND drain plugs, so if your transmission doesn't have the drain (only the fill), it's not the original main case. Before then, only the M22 had both the fill and drain plugs and the M20 and M21 drain plug boss wasn't drilled.

Ed

garygnu

would a little heat from a propane torch ,then the frezze off work better ?use a little anti-seize on the plug when you install it .

DUB

It takes a special 8 point socket to remove the plug. Using an open end wrench is a big mistake...or can be quite quickly.

DUB

7t9l82

propane torch , heat the plug , melt candle wax onto the threads, it worked for me. i agree 8 point socket.

Gale Banks 80'

Generally dissimilar metals are less likely to seize. Stainless to Stainless its very common the gall when the parts are new and its screwed in for the first time. Aluminum to Aluminum is not much better.
I work in the marine industry and we get parts that have been out in saltwater for 30 years or more we need to get apart. Nothing beats Heat, if You can heat a bolt till its red and let it cool back down it will just about fall out. Two reasons the heating breaks loose the rust, and when the bolt cools down it will be smaller in diameter than it was new.
Maybe a Trans case in the Car isn't the best place to be doing this, but the Freeze idea is doing the same thing, its just a lot more convenient in this situation.

ukgeza

Thanks for the advice. I wound up taking it to AAMCO. As it turned out the front and rear seals where bad as well as the side cover gaskets, all old and perished. They did a good job replacing all that lot. Car runs great now. Just gotta replace the distributor. ( posting new question related to distributor subject).

bashcraft

Muncie's don't have a front seal. Did they charge you for one?