Guys, I found a nice 72 M20 for my car and will plan to swap it out for the 68 M20 that is in there now ( unfortunately, the original trans is long gone, but the M20 is a much nicer trans I think). In any case, will the dimensions of the 1972 M20 be the same as the 1968? Hoping to avoid any driveshaft updating. Happy Thanksgiving to all!! Thanks , Steve
The 1968 M-20 will have 10 spline input/27 spline output and have 3/8" studs to attach shift levers... The 1972 M-20 will have 26 spline input/32 spline output and use 3/8" bolts to attach shift levers, and the tail housing is 3/4" longer... Hope this helps... Crash
I didn't realize the tailshaft was longer on the `72 trans. My mistake, but just for general information, Crash has been rebuilding these transmissions for as long as I can remember so you can take what he says as gospel. Good to know for anyone with questions about manual transmissions. Eric, welcome to V8Buick. Your expertise will be greatly appreciated here :TU:
Steve, if you use the 68 M-20, you will need to swap out for the correct shift shafts for your reverse lock out & linkage tabs to fit, as the 68 are threaded for bolts and the 70 have studs. Here are pics of 68 shift shafts: http://www.v8buick.com/attachment.php?attachmentid=169006&d=1275275967 I just went back and read your post again and see you have been running the '68 and looking at switching to the '72. The '72 should have the correct shift shafts in it already; you should check. If you have '70-'72 linkage in your car now, the '68 must have been swapped already. If not, you should check what set up is in there. MarkO
I am doing this same swap (almost, large OP, fine spline IP muncie) into a 70 skylark automatic car. I need to cut the hole in the floor and would like to position it in the correct spot. I have a factory 70 GS shifter and will be keeping my bench seat. I have noticed that the 71 transmission only has 3 mounting holes for the shifter bracket where the older transmissions had 5 or 6. I also have heard that the mounting position of the shifter bracket will be wrong for my car if I use the 3 holes present on the 71 transmission, which would result in me cutting the hole in the wrong spot. Anyone run into this problem, and if so, how did you overcome it? thanks Jess in ky
Jesse, Could you post a picture of the shifter mount you have... Crash Or E-mail the picture to: crash_enterprises@yahoo.com
Finally getting to repsonding to this post. Sorry it took so long. Thanks for the advice. I was hoping for a direct swap ( with a clutch change , of course), but looks like the extra tailshaft length will be an issue to consider. Also don;t have any idea if the 68 trans is set up with correct shift linkages. Need to look at that. Never simple.. Thanks again. Steve
Steve, my M-20 is a '68 that I swapped out the shift shafts to be compatible with my '70 linkage. The shift shafts are readily available and not too expensive. Mark
Mark, thanks. This may be a dumb question, but will the add'l tailshaft length neccesitate shortening of the drive shaft ( or getting another one)? Could I use the 68 tailshaft on the 72 M20 and avoid the dimension change? Thanks, Steve
Steve, You would have to swap out the main shaft with the tail housing to do what your thinking... Just have a new drive shaft made... Crash
