Never, and I mean NEVER attempt to put a long shaft Muncie (M20) into a 61 to 64 Bonneville.  These cars were built with a long shaft Borg-Warner T-10. Although the transmissions are close to the same length, they are totally different in two major ways.  #1:  The transmission mount is 10″ too far forward on the Muncie verses the T-10 and will not line up anywhere near your cross member.  #2:  The shifter comes up 1.5″ too far forward and 1″ closer to the center of the transmission hump.  The regular 63-64 Bonneville shifter porch (which we reproduce) will not line up or work with the Muncie.  The long shaft Muncie was used in 65 to 68 full size Pontiacs and Buicks.  BTW, I have now found long shaft T-10’s with one or two mounting blocks on the tailshaft (Bonnies use the rear one) and Muncie long shafts with different mounting block locations as well.  When in doubt, use the original equipment to the car.  Saginaw transmissions have the same basic problem in 61 to 64 Pontiacs as the Muncies.  Therefore, I recommend that you only use the original transmissions to your car.  61 to 64 Catalina and 62 to 64 Grand Prix:  Short shaft T-10.  61 to 64 Bonneville:  Long shaft T-10.  65 to 68 All Full Size Models:  Long shaft Muncie M-20.  These are all somewhat easy to find.

Also, never put a Muncie into a 61-64 Catalina or Grand Prix….same problems as above.  Always use a T-10 in these car for 61 to 64.  The Bonneville T-10 is a real bitch to find.  It is 2″ longer than a regular T-10.  Pontiacs T-10’s always had cast iron cases and aluminum tail shafts.  If your T-10 has a Chevy bowtie, it’s not right! The somewhat good news is that the Hurst Competition Plus shifter is the same between the Muncie and the T-10.  I order mine from Jegs.  The shifter is #391-7308 and the installation kit is either 373-3163 for a Muncie (65 to 68) or 373-4734 for your T-10 Bonnie, Catalina and Grand Prix 61 to 64).  Remember, if you have to move your cross member, your parking brake is SERIOUSLY affected.

Some people think that just because GM stopped using T-10’s in big cars in 1965, that there was some dark reason.  No, GM built and owned Muncie and the decision was made to enter into the 4 speed business in 1964 starting with A body and full size Chevys.  In 65, the Muncie 4 speeds found  themselves in full size Pontiacs and Buicks.  Ford used T-10’s well into the 80’s.  GM also returned to Borg-Warner using Super T-10’s in Camaros and Firebirds.  BTW, here’s a little known fact….Saginaw, which made all of the Pontiac 3 speeds, burned to ground in 1964.  If you had a 65 thru 67 A body or big Pontiac with a 3 speed, it was a Ford Top Loader with a Pontiac bolt pattern at the bellhousing!  Saginaw did not start doing 3 speeds again for Pontiac until 1967!  Great transmissions with a full syncro and a 2:70 first gear!  Many a Pontiac was drag raced using these 3 speeds.

Last but not least is which transmission do you have?  And furthermore, which transmission should you put in your car?  This is based on your rear end.  You need to determine what rear end gears you have.  Here is how to find out:  Jack your car up with the rear wheels off the ground.  Put your car in neutral.  Using chalk, mark your driveshaft and the rear yoke in the same line.  Then mark your right rear tire on the inside spin the tire and count how many times the driveshaft goes around.  2.7 times = 2.69, a little over 3 = 3:08, almost 3.5 times would be 3:42’s…etc.  Rule of thumb…..if you have 3:55 or higher gears (3:23, 3:08…etc), you will want to use a wide ratio 4 speed.  If you have steeper gears (3:70, 3:90’s …etc), you will want to use a close ratio 4 speed.  OK, how do I tell what transmission you have?  Click it into first gear.  First gear is the rear lever on the side cover. You will click the post to the rear to get into 1st gear.  Use a Cresent wrench. Then, spin the rear shaft over one complete time counting how many times the front shaft turns Chalk is go here too.  2:20 times is a close ratio.  2:54 times is a wide ratio.  Same for either T-10’s or Muncies.  If you use a close ratio with highway gears, your car will fall flat on its face when you let the clutch out.  Same way in reverse using a wide ratio with steep gears.  It will be like driving grandpa’s old pickup starting out in granny 1st gear.

In closing, there are a lot of issues to address when converting your 61 to 68 full size Pontiac to a stick.  I am still learning more everyday. Hope this helps!  LK  9-22-2018

PS:  I am still working on the stick conversion papers I spoke of earlier this past year.  Please hang in there!

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