GM Musclecar Transmission Mounts Energy Suspension 3-1108G & 3-1158G Applications

If you spend time researching GM Transmission Mounts Online with Various Forum Posts there is alot of Confusion what exact GM Used for Transmission Mounts Musclecars made from 1963-1974 & into the Disco Years to 1981 with the Firebird & Camaro.

The Early 1970-1/2 -1974 Pontiac Firebird Trans Ams & Camaro Z-28 all had the Turbo 400 Automatic Transmission or the Muncie 4-speed M20, M21, & M22 Manual Transmissions.

I own a 1970-1/2 Pontiac Trans Am RAIV  Muncie 4-speed Musclecar. The Transmission Crossmember has the 2-bolt pattern TH400 style transmission Mount Pad.  Used all GM Musclecars 1965-1974 with the Turbo 400. It takes the Shorter GM Trans Mount.

Energy Suspension # for the 1970-74 Pontiac Firebird & Trans Am Line with a Pontiac V8 is 3-1158G. It measures 1-5/8″ tall or 1.625″ inches.

1974 was the Last Year for the Turbo 400 transmission in the GM F-body line for Pontiac & Chevrolet. 1975 -1981 the Turbo 350 transmission was used because the TH400 would no longer fit beside the Huge pellet catalytic converter introduced to meet anti smog laws.  These years used a Single stud transmission mount that had a Taller Height of 1-15/16″ or 1.9375″ inches.  Same holds True for the Borg Warner Super T-10 transmission used in the 1975-81 F-body.

Energy Suspension Transmission Mount for 1975-81 F-body Pontiac is 3-1108G.

Keep in mind the that Pontiac V8 engine Firebird & Trans Am had unique Frame Bracket Mounts used for years 1970-71. Then 1972-74 style. And then for 1975-79 with the Pontiac 350 & 400 cubic V8. The Pontiac 301 & 265 V8 Firebirds & T/A had different engine Mounts yet.

And I recall that Pontiac Firebird & Trans Am 1970-74 had different part number steel trans cross members for the the TH 400 & for the Muncie 4- speed cars.

Start mixing up parts from cross over years & you will have driveline install issues & driveshaft Pinion Angle variations from factory Stock.

Review again :

Energy Suspension 3-1158G (Black Polyurethane) is for Turbo 400 & Muncie 4- speed stock Musclecars 1965-1974.  Also fits 1963-64 Chevy Nova II V8.

Energy Suspension 3-1108G (Black Polyurethane) is for Turbo 350 & Borg Warner Super T-10 stock 1975-81 Pontiac Firebird & Chevy Camaro. With a Pontiac V8 or Chevrolet V8.

When in doubt you can double check measure your original factory transmission mount also.

Just 3/16″ or .3125″ inches difference between the GM TH400 & TH350 transmission mount heights but will change your transmission driveshaft rear differential pinion angles.

Brian R.

Capture.PNG 3-1158G

Capture.PNG 3-1108


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