1968 Pontiac Firebird 4 Speed Muncie
Transmission Work Page 1

I got my 4 speed muncie out of my first 68 bird. It was hooked up to a small block chevy. The
previous owner said it worked well last time the car was used. What I should have done was
start the car and drive it it to make sure I knew what worked and what did not. But I didn't.
I pulled the transmission, drained the oil and then it has sat for the last 6 years waiting for
me to rebuild it. Well that time is finally here..


I likely had the experience many people have. The brief hope that it was an M22.

The identification sites I found (like this) describe what to look for. 1st the input shaft.
If it has no rings in it it is supposed to be an M22. I saw.

No rings.

There are several numbers to check:

Case casting number : 3925660 = 1968-70 1" bore also consistent with M22

excitement was building...

but when I opened up the side case I see..

That angle means they are m20 gear set. Oh well. Muncie are still Muncies. It should be fine.
good news is the teeth I see look to be in good shape.

Oct 17, 2009. FINALLY broke open the case on the transmission. I have a book called
"Camaro Owners Handbook" from HP Books. I know it's a Camaro book but my car
shares so many parts and chassis similarities with Camaros that the book is actually
quite good. And the market for "Firebird Owners Handbook" I guess is not worth the
effort for some enterprising author. Too bad. I would buy one.. Anyways the book has
a great, well-illustrated chapter on rebuilding a Muncie transmission. It has been my
main resource, as well as a Camaro factory service manual I have.

started with some pics of the case before dissassembly. The side cover bolts are out.

and the linkage removed.

another shot so I have the exact placement of the rods.

labelled the forks so I get them back in same position.

and the inside and outside of the side cover.

 

removed the tail housing 6 bolts and seperated the two main pieces.

shot of the end of the main output shaft. Book says speedo gear has a
retaining clip, but mine is pressed on.

and right away see what my damage is . The reverse Idler gear is pretty chewed up.
i found them on the net pretty easy. Think I will order one off ebay.

shot of reverse shift fork retaining ball. spring fits in housing.

to remove the mid plate off the mainshaft this snapring has to be removed.
I got it off, but I need to get a better set of snap ring pliers to put these back
on. pretty tough snap rings. One site described these as "gorilla-class" snap rings
and I think that was a good description.

starting to get a pile of parts. I took more photos so I remember where everything goes.

put some dots on mainshaft before I started disassembling it. a lot of gears here.

another couple of "gorilla class" snap rings on main shaft.

 

some shots of how the slider sleeves tensioning bars fit.

with one of the inner springs removed and sitting on top.

tailshaft seal removed. Also punched out the tail shaft bushing,
but forgot to get shot of that of course.

and scraped off all the gaskets and silicone.

and all the main housing and linkage parts after degreasing ready to be blasted.

and the parts after Blasting

 

 

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