[1973T/A]

I have a 73 trans am and it has an auto in it... the motor looks to be a numbers matching YC code 455. Stamp is very hard to read. But i have the dealer invoice and it shows its a 4 speed car with the performance axle.. I'm just confused.. any help would be awesome.

[Brewster]

YC code represents an automatic. Are the vins a match?

[1973T/A]

Yeah thats why I'm confused. Gonna get it over the pit in the shop and take a better look. Stamp is not very good. But it looks like it is numbers matching.

[johnta1]

Not sure it would show if it was a TH400 or 4 speed?
(4 speed was standard, auto was no cost upgrade I think?)

As was suggested, see if the partial VIN matches the car.

I'd say the car is an automatic and this is the original engine?

[1973T/A]

Could you get the performance axle with an auto tho..?

[GREGGDOG]

I think the dealer invoice shows just what was standard on the trans am. The left side lists this standard T/A package (notice how it reads "and more"). The right side of options are "your individual options." I thought Automatic was an option. Performance axle was available in auto as well I believe.

[Brewster]

Yes, you guys are correct regarding standard on the manual and my phs even said manual for my SD which is an XD car or automatic code. Well thats when I learned about paper work.
The axle was standard with the TA package along with some other upgrades.

[hada76]

later yrs had different gears for auto/stick cars

[1973T/A]

Originally Posted by GREGGDOG

I think the dealer invoice shows just what was standard on the trans am. The left side lists this standard T/A package (notice how it reads "and more"). The right side of options are "your individual options." I thought Automatic was an option. Performance axle was available in auto as well I believe.

So if was an option wouldn't it show it on the right side of the invoice? Also show show it on the PHS?

[1973T/A]

Since the car does not have air.. And it has the performance axle it has 3.42 gears correct?

[GREGGDOG]

If automatic was a "no-cost" option in 73, it would not show - much like honeycombs and rally II's? My 73 came with honeycombs, however it was not listed on the PHS. as rally II's were standard and honeycombs a "no-cost" option, or "choice."

Here's an old thread with a 73 owner showing auto as a no-cost option that doesn't appear on PHS...

http://forums.maxperformanceinc.com/...ans+PHS&page=3

[1973T/A]

Originally Posted by GREGGDOG

If automatic was a "no-cost" option in 73, it would not show - much like honeycombs and rally II's? My 73 came with honeycombs, however it was not listed on the PHS. as rally II's were standard and honeycombs a "no-cost" option, or "choice."

So there is no 100 positive way to prove it was a manual or auto without the buildsheet?

[GREGGDOG]

Originally Posted by 1973T/A

Since the car does not have air.. And it has the performance axle it has 3.42 gears correct?

It may in fact have a taller gear (3.73?) as 3.42 was standard for a 73 T/A
without air. Performance axle was an extra cost option.

[1973T/A]

Originally Posted by GREGGDOG

It may in fact have a taller gear (3.73?) as 3.42 was standard for a 73 T/A
without air. Performance axle was an extra cost option.

Far as i know 3.42s were the lowest gears you could get in 73. Then if you had air you got 3.08s because my other 73 has air, auto and 3.08s.

[GREGGDOG]

Originally Posted by 1973T/A

So there is no 100 positive way to prove it was a manual or auto without the buildsheet?

Your build sheet is gospel. Your block code is your "proof" now. A bit scary when you think about the 4 speed cars out there, even scarier when you think about how few 73's have build sheets.

[GREGGDOG]

Originally Posted by 1973T/A

Far as i know 3.42s were the lowest gears you could get in 73. Then if you had air you got 3.08s because my other 73 has air, auto and 3.08s.

It looks like 3.08 was the standard axle, a/c, or non. Performance would upgrade you to 3.42.

http://forums.maxperformanceinc.com/...ce+axle&page=2

[RicksGTO]

I would take some white-out or something similar and smear it into that partial VIN on your block, then wipe it down lightly and those numbers will be a lot easier to see. Also there should be a partial VIN on the transmission on the driver's side if it's like my '72.

[REEDRACER]

I didn't know about the no cost option for transmissions, until I asked PHS why the paperwork doesn't show my 4sp on it. My car is a ZZ motor, my 4 speed is long gone. It got stolen when the motor was rebuilt and the original owner stuck a auto in it, not sure why. So if 1973T/A's car is truly a 4 speed car, what Muncie would it have? I have know idea what Muncie my car originally had. Wish I had a build sheet for my car.

[Brewster]

The M20 would have been the standard transmission for 73 Trans Am's hoevever the M21 was optional. The gear ratio changed with (3.08) or without air (3.42) on the super duties. Not sure about the standard TA's??
ZZ is correct for a manual coded motor in 73

[hada76]

found this on another forum, good info about trannys


Muncie 4 speed transmissions were used in General Motors cars from 1963 to early 1975. These gear boxes were used when power levels exceeded the limits of the early Borg Warner T10 4 speed. It was actually based on the T-10 design and uses the same basic gear layout. The T10 made it's appearance in GM cars in 1957. From 1957 to 1963 many changes took place inside the gearbox to meet the increasing horsepower the new engines were putting out. It was replaced by the Muncie in late 1963. The Muncie 4 speed was used in production vehicles until power levels dropped in 1975. 1975 was the first year catalytic converters , smog pumps, and low horsepower were introduced. These new requirements led to the demise of the Muncie and the reintroduction of the improved T10 called the Super T10.
While General Motors was switching gearboxes around from 1963 to 1975 other companies such as Ford and AMC kept the T10 in production. So we got to see T10, and First Design Super T10 transmissions end up in these cars. It was also an opportunity for Borg Warner to design replacement Super T10's for the Muncie. These 4 speeds offered 9310 nickel gears, had a wide variety of gear ratios, and were available from any auto parts store carrying the Borg Warner parts line. A variation of this Super T10 ended up in GM cars from 1975 to 1983. Also as the 4 speed section of the 4+3 Corvette Overdrive in 1984 to 1988 Corvettes.