Originally Posted by black69 (Post 1355482)

Another point of information is this car has a close ratio 4spd (few made?) and has the more desireable rear end ratio (3:42). This car would be in the 13 second range which was amazing for 1973. On the other hand, a 73 SD w/automatic with air conditioning would have a different rear end ratio (3:08) that would put it at a disadvantage. That version would be in the low 14s.

Not all 73 SD 455s Trans Ams were created equal. This is one of the fastest ones that put it into the performance range of 70 hemi cars, etc. which was just mind blowing for the times.

The more I learn about this car, the more I like it....

Originally Posted by njsteve (Post 1355501)

Sorry about that, my typing overtook my memory recall ability. The close ratio Borg Warner Super T-10 started in 74 and was used in the 74 SD455 cars. The SD455 still had Muncies in 1973 but if I recall correctly, it was the M20 wide ratio. The regular 455 got the close ratio M21, (the M22 got dropped after 1972).

BTW, all the transmissions used the "M" in front of the number regardless of who made them (not just Muncie) and what year.

There's some SD455 trivia on the trans question half way down the page here: http://www.angelfire.com/mi/jamos1/sdtrivia.html

Originally Posted by olredalert (Post 1355609)

----I'm sure that the wide ratio M-trans helped that 3.42 geared SD get those kind of quarter mile times......Bill S

Originally Posted by njsteve (Post 1355488)

3.42 was the rear end ratio for stick cars and 3.08 was for the automatic cars with or without A/C. (No A/C allowed in stick cars). All the four speed transmissions were the same internally and were no longer built by Muncie in 73.

You are quite correct- these cars are scary fast. And to think that they accomplished all this with 8.6 to 1 compression!

If there is one version to have of a SD455, it would be a stick car. (Unless you're old like me and need to be refrigerated and have the shifting done for you) :-)

Originally Posted by njsteve (Post 1355803)

That is correct. From personal experience I think the autos run better with the 3.08 rather than the 3.42.