[kenneth77]

hello,,i just recieved as rebuild kit for my 4spd muncie. after i had mounted the countergear shaft,it was not flush in the front end of the case.it was sticking out 0,035". the machined part in the other end was in place.either the shaft was to long,or my main case have been machined. DOES ANYBODY HAVE THE CORRECT LENGHT OF THE MAIN CASE ON A 4SPD MUNCIE,OR HAVE THE CORRECT LENGHT ON THE COUNTERGEAR SHAFT. i need to find out if the shaft is to long,or the case have been machined.
i will go and measure my main case and the shaft.

should the shaft somehow have a overlenght,to like get it "compressed" when you tighten the bolts? like thousands of an inch or something??

the trans is a originally muncie in my 1966 gto



thx

[Jurassicgto]

I just rebuilt mine. The shaft should not stick out the front at all, or else it will hit the bellhousing and the case will not sit flush. Do you have the stepped side of the shaft to the rear? Thats the side that should stick out the back to fit against the rear bearing plate.

[kenneth77]

the machined part or the stepped side is at the rear.
i was now at the shop and measured the parts.

main case : 9 7/8"
countergear shaft 9 29/32"

either the main case have been machined some time,or the shaft is to long..

[kenneth77]

Jurassicgto, do you have the measuremnts on the old countergear shaft?

[67FB400-4SPD]

Do you have those washers at each end with the crimps in them? If so then you are good. I had the same issue with my 69 m-20 and I just rang it good with a brass hammer and it flushed it right up nice and tight. No problems...just make sure before you set the shaft that the stepped end of the shaft is turned at the right angle as to not interfere with the bearing plate as JurassicGTO said above. Jason

[Jurassicgto]

I came up with 9 7/8" on the case also and 9 13/16" on the shaft. Your shaft is too long.

[Jurassicgto]

I measured the shaft on the shortest distance.

[67FB400-4SPD]

I would give these guys a call and make sure that everything is cool before you go any further...they can be a great help and should be able to help you out with this weird length issue...Jason.

Riverside Gear
Eaton Rapids, MI 48827
Tel – 1.517.663.4410
Fax – 1.517.663.4351
Toll Free - 1.877.614.4327

http://www.riversidegear.com/categor...eed/index.html

[kenneth77]

so what you say is that when the trans is assembled,i just take a brass hammer,and hit the countergear shaft thats sticking out at front of the case,and make it flush??

[kenneth77]

i looked at the riversidegear internet site. i see they sell different kits for 1964-1965 muncie,and 1966-1974 muncie. what is the difference between the trans?.
only thing i know of is the lenght of the pipe spacer inside the countergear.
my trans needs 4 0,050" washers in the countergear,some other models needs 6.

i belive since my car is a 66,the trans was made in 65,thats make it 65 model?

[67FB400-4SPD]

Originally Posted by kenneth77

so what you say is that when the trans is assembled,i just take a brass hammer,and hit the countergear shaft thats sticking out at front of the case,and make it flush??

That is what I did and it worked perfect, but as you said above it was only sticking out about .035" or so in the front. If I remember correctly, I also had an issue with those 'crimped' washer tabs on each end of the shaft. One of the washers was being stubborn for me and kept rotating. I dabbed a nice cold chunk of bearing grease on it to keep it in place and that seemed to do the trick, otherwise that little bent tab on the washer would make it sit crooked when it was not sitting in that indention where it belongs. As far as the year you have...you should be able to research the year you have by the part numbers on each piece. The main case, tail housing, and cover should all have the part numbers on them...especially the main case in your situation.
If you let me know what those numbers are I can probably help you look it up when I get a chance. Hope this is helpful for ya...Jason.

[67FB400-4SPD]

Check these maincase numbers to match yours:

Maincase Gear Ratios Input Grooves Cluster Output
RPO Years Casting 1st 2nd 3rd 4th Spline (Input) Pin Spline
-----------------------------------------------------------------------
Muncie
M20 63-65 3851325 2.56 1.91 1.48 1.00 10 None 7/8-inch 27
M20 66-67 3885010 2.52 1.88 1.46 1.00 10 2 1-inch 27
M20 68-69 3925660 2.52 1.88 1.46 1.00 10 2 1-inch 27
M20 70 3925661 2.52 1.88 1.46 1.00 10 2 1-inch 27
M20 71-74 3925661 2.52 1.88 1.46 1.00 26 2 1-inch 32

M21 63-65 3851325 2.20 1.64 1.28 1.00 10 1 7/8-inch 27
M21 66-67 3885010 2.20 1.64 1.28 1.00 10 1 1-inch 27
M21 68-69 3925660 2.20 1.64 1.28 1.00 10 1 1-inch 27
M21 70 3925661 2.20 1.64 1.28 1.00 10 1 1-inch 27
M21 71-74 3925661 2.20 1.64 1.28 1.00 26 1 1-inch 32

[kenneth77]

main case is 3885010
tailhousing is gm 3846429
cover is gm 3884685
midplate is 3831752
front bearing retainer 3851326

top of main case is also stamped with the last vin digits

[67FB400-4SPD]

66 main case is 3885010
65 tailhousing is gm 3846429
66 cover is gm 3884685
?? midplate is 3831752
66 front bearing retainer 3851326

I would say that you are good as far as years go...the midplate part number shows as M-20 and M-21 for many years including 66.

[kenneth77]

the company i bought the parts from will send me a new shaft,and gaskets for free.
i also have to shim out the front bearing to get the same clearaence on the 3rd and
4th gear syncronizer rings.

however they stated that the lenght of the countergear i got was the same as they had in stock.i dont understand how it will fit as long as it is 9 29/32" and the case is
9 7/8"... maybe i just have to grind off some of the shaft,or make a "hole" in the bellhousing for the shaft

[67FB400-4SPD]

Good deal but don't grind into the bellhousing...if the shaft being replaced will be the same length I would suggest using a light sanding disc like a flap wheel or something to knock it down a bit. If you already slid it through all those little bearings in the countershaft that kind of sucks to do it all again but I guess that is the nature of the beast. You could order just that shaft from another supplier as the one I mentioned above. I have had absolutely no problems with any of their parts. Good luck to you...I am sure it will work out fine for you in the end. Jason