I have a muncie still installed in a old truck and would like some help identifing it without pulling from the vehicle, any quick help would be appreciated.

First, get ALL the numbers you can find, and post them here. Try to get the number on the top center section of the trans. Are the shift plates held on by a nut, or a bolt? Does it have a drain plug (2 plugs..one kind of in the middle of the main case, and one near the bottom.)
Do the RPMs drop way off from 3rd to 4th gear?

Forget the numbers. That's too much like work.

Look at the clutch gear, where the clutch slides on. If it's got 10 splines and 2 grooves cut around its circumference, it's a M-20. If it has 10 splines and 1 or no grooves, it's a M-21. If it has 26 splines, it's a M-22.

A quote from http://www.5speeds.com/muncie2.htm

Please note that there are 7 different Muncie input shafts. All 26 spline inputs came with 32 spline output shafts and all 10 spline inputs came with 27 spline output shafts. A common mistake is thinking that all "fine spline" 26 spline input shafts are M22 heavy duty types. This is not true. An M22 gearbox has a 20 degree helix angle on the gearset as opposed to a 45 degree angle. Also M22 gear sets were of a higher nickel alloy. The straighter angle was designed to produce less end loading of the gear train and less heat but created more noise, thus the nickname "rockcrusher". The higher nickel alloy allowed for more impact of the gears. Another misconception is if you have a drain plug you have an M22. Again this was only true when the first M22 boxes were created. But all 3925661 castings had drain plugs.

I hope they didn't keep the truck bellhousing. I just went through one that that had happened. Some rather badly worn input related parts.

Right, the truck BH has a hole about .4" diameter larger than a car transmission's clutch gear bearing retainer. Don't know the exact dimensions off the top of my head; but I had a machinist friend make me a spacer ring one time, so that I could use a truck BH I had on hand.

All of that about the 26-spline shafts is interesting.... personally, I've never seen with my own eyes, a 26-spline Muncie clutch gear, that had anything other than the straighter-cut gears. Not to say that they don't exist; but still....

I had a large input shaft on an M21 that I put in a 64 Chevelle road racer.

RB69SS, I have a '72 Buick Stage 1 G.S. thats muncie has the big 26 spline input shaft with no ring but is a M-21 and not an M-22. I looked at the gears once.

Originally posted by RB69SS396Conv:
Forget the numbers. That's too much like work.

Look at the clutch gear, where the clutch slides on. If it's got 10 splines and 2 grooves cut around its circumference, it's a M-20. If it has 10 splines and 1 or no grooves, it's a M-21. If it has 26 splines, it's a M-22. The original post said "without pulling it from the vehicle" Thus the request for any/all numbers on the trans to Help identify it. After 35 yrs, anything could have happened to these tranys.
The numbers would help determine what it was originally...whether or not it is still original is anyones guess.
ALL Original 661 (late 70-74 ) cases have 26 spline input regardless of ratio.
M-22s were made with both 10, and 26 spline input shafts. graemlins/beers.gif

I know m22's came with the coarse spline inputs,I have one.It has the C at the end of the # on it.They do exist.