OK!
Get your specs on and get ready to read!
I've put this run down together with information I gather from several reliable sources.
I hope it helps.
The BORG Warner T10 transmission was manufactured from 1957 to 1987.
Cast aluminum units are Super-T10 models, introduced in 1966 and manufactured until 1987.
There are many different variations of the Borg Warner T10 four-speed manual transmission,
because from 1957 to 1987, every American vehicle manufacturer has used the T10.
The two major classes of the T10 are the early cast-iron unit and the cast aluminum Super-T10.
Late '50s and early '60s Corvettes used an aluminum case, while the full-size GM units from '57-'60 used a cast-iron case.
GM used all aluminum-cased units after 1960, and all manufacturers used aluminum cases up until 1974.
All of which can have different gear ratios.
Basic identification is simple.
However, determining the different gear ratios of the T10 requires the transmission to be off the vehicle.
To determine the gear ratio, count the cross-grooves on the input shaft.
Since there are many gear-ratio variations of the T10, there are identifying grooves cut across the clutch spine of the input shaft.
The groove count of the four common T10 first gear ratios are as follows:
the 2.43 first gear ratio has two grooves,
the 2.64 first gear has three grooves,
the 3.42 first gear has five grooves,
the 2.88 first gear has six grooves.
The gear ratios ultimately identify the T10 in question.
If the input shaft has 26 splines, it's a Power Brute Super 10, if the input shaft has less spline and an aluminum case, it's a Super 10.
Cars that used this transmission as an original equipment unit, were:
1957-'63 Corvette
1957-'63 Chevrolet full-size sedan
1961-'63 Pontiac, Olds F85, Buick Specials
1960-'65 Ford and Mercury full-size, except station wagon
1960-'65 Ford Fairlane, Falcon, Mustang, Mercury Comet
1963 Dodge and Plymouth V-8, except Hemi
1968-'70 AMC Rambler, Rebel, Ambassador, Marlin, and American
1971 AMC Hornet and Matador
1968-'74 AMC Javelin and AMX
Original Manufacturers specified different shift ratios for their own cars; and there were several for each manufacturer available.
Ford used a 2.73 first gear in the Falcon, Comet and Mustang models, and a 2.36 first gear in their larger cars and the Shelbys.
Chrysler used both a 2.54 and a 2.20 first gear in the 1963 production year, depending on engine size and rearend ratios.
GM also used a 2.54:1 ratio and a 2.20:1 in the Corvettes, initially, and added the 2.64:1 and 2.43:1 ratio in both their aluminum and cast-iron cased versions.
AMC used a 2.23:1 ratio as well as the 2.64:1 and 2.43:1 ratios.
The most popular version of the T-10 among enthusiasts is the Power Brute Super T-10, which was used on the 1974-'82 GM A-Body (Chevelle/Nova) and F-body (Camaro/Firebird) cars.
The Super T-10s used a 26-spline input shaft and were built to withstand the higher rpm requirements for the larger muscle car engines.
These can be easily identified on 1974 and up GM data tags as an M-18, M-21 or M-24 transmission designation.
