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GM Automatic Transmissions

 

The venerable Powerglide transmission has been GM's staple for automatic transmissions well before the introduction of the Chevelle in 1964 and was used through the 1972 model year. Mainly used for low horsepower I6 and V8 engines with the exception of the 1966-1968 SS 396 L35 and L34 engines. Gear ratios varied depending on the engine. You can download GM's Information Kit either from the GM Archives website or here on my Chevyworld.Net website.

 

The TH350 is a medium duty automatic transmission built from 1969 to 1989. It was used behind 6 cylinder and small V8s engines and was designed to handle up to 425 pound feet of torque. The TH375B is a heavy duty TH350. The 700R4 in 1992 became the 4I60. Later the E was added to mean electronic shifting. For those who are wondering...

The 4 is 4 speed, L is longitude, (rear wheel) and 60 is a rating for strength. The higher the rating the stronger the trans. The 3L80 is a renamed 400. The 3L80HD is a 475. The 4L80 is a 400 trans with OD, and the 4L80E is electronic.

The 2004R and the 700R4 have overdrive planetary gears and use a lock up converter. The 2004R and the 700R4 are very close in torque rate. The 2004R has a deeper OD and deeper 1st, 2nd, and 3rd gears. Anyone thinking of buying a 2004R, be sure it says METRIC on the pan. If it doesn't, you're getting a plain 200. Also, in case someone wanted to know, a "T" in the trans designation means transaxle. (Front wheel).

 

Gear Ratios

 

Popular Transmission Ratios
See RPM Calculator page to determine wheel/tire combination speeds
TRANSMISSION 1ST 2ND 3RD 4TH 5TH
GM Muncie (M20) 66-74 (1) 2.52 1.88 1.46 1.00 n/a
GM Muncie (M20) 63-65 (1) 2.56 1.91 1.48 1.00 n/a
GM Muncie (M21/M22) (1) 2.20 1.64 1.28 1.00 n/a
GM Powerglide (low hp) (2) 1.82 1.00 n/a n/a n/a
GM Powerglide 1.76 1.00 n/a n/a n/a
GM Turbo Hydra-Matic 350 2.52 1.52 1.00 n/a n/a
GM Turbo Hydra-Matic 400/4L80E 2.48 1.48 1.00 0.78 n/a
GM Turbo Hydra-Matic 2004R 2.74 1.57 1.00 0.67 n/a
GM Turbo Hydra-Matic 700-R4/4I60E 3.06 1.63 1.00 0.70 n/a
           
(1) Manual transmissions shown for comparison only
(2) Low hp are typically I6 and engines with 250hp ratings or less.

 

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