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post #1 of 3 (permalink) Old 12-28-2015, 08:33 PM Thread Starter
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4spd trans question

Currently, my LeMans has a Saginaw transmission that I believe came out of a late 70's early 80's Camaro or Firebird. I matched it up using a tail shaft chart I found on line.

This trans is extremely noisy and I am looking at replacing it with another 4 speed. I have a few options available at different price levels. Here's the question; other than the input spline and shifter, are there any differences in how the different transmissions used by GM would install? That is, are the rear mounts in the same location on all transmissions and/or are the different transmissions all the same lengths? I don't want to get into a major fabrication job here, I just want to swap out the noisy trans I have with another one.

I am leaning towards either a Muncie or a Borg Warner. Any opinions? Since I already have the wrong trans in the car anyway, originality is not my biggest concern.

Thanks in advance.
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post #2 of 3 (permalink) Old 12-28-2015, 09:31 PM
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Saginaw 4 speeds all had the coarse spline (10 spline) input shaft. They also accept the same small output shaft yoke same as used behind '64-70 Muncie 4 speeds, '64-68 Super Turbine 300 2speeds, and '69+ turbo 350's.
The same length driveshaft is used when one interchanges transmissions among the above four.

A '68-70 Muncie 4 speed GTO driveshaft will measure 56.00" center of u joint to center of u joint. For '71 models, the big output shaft Muncie was introduced. It uses the medium length Turbo 400 yoke. The driveshaft used in '71-72 Pontiac 2 door Abodys with factory Muncie 4 speed or with shorttail Turbo 400's measures 55.375" center to center on th ujoints with stock usage rearends (Pontiac 8.2 or McKinnon built 12 bolt). If the car has been upgraded to the 8.5 A body rearend, will have to shorten the factory driveshaft 7/8".

Borg Warner T10's from the early '70's are typically AMC usage and used a coarse spline input shaft. Many T10's were also sold through Speedshops (true Super T 10's) with high nickel gears in a variety of ratios, the majority of which can be bolted in place of a '64-70 Muncie 4 speed.

In the mid '74 model year, Borg Warner introduced the 2nd design T10, these were used in GM performance vehicles of that era. These 2nd Design T10's were often referred to by magazine writers as Super T 10's, but they are not the heavy duty true SuperT10's one could still buy during this time through Speedshops. This misusage of the term Super T10 continues to today, just like a bunch of yahoos refer to any big output Muncie 4 speed, not just factory M22's, as a "RockCrusher". Been very frustrating over the years dealing with ignorant sellers.

The latter 2nd Design T10 for GM applications also take the med length Turbo 400 yoke, also has 3 mounting bosses on the tail housing just like the '71-74 Muncie 4 speed. The crossmembeR trans mount also bolts in the same spot, and one can interchange same length driveshafts with the '71-74 big output shaft Muncie transmissions.

Last, though 4speed shifters can be interchanged between Saginaw transmissions and Muncies, the shifter rods (linkage) are different. Hope this helps.
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post #3 of 3 (permalink) Old 12-29-2015, 07:15 AM Thread Starter
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That helps a lot. Thanks!
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO Undercarriage, Frame, Transmission and Differential Discussions.

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