[bosox30]

Hey guys i just bought a 77 rally , i know you can tell the rear end gear ratio 2 ways, 1. on the front right axel tube its has alpha numeric symbols(TAC71) thats all i can read 2. inside the differential (GM 3984822 6:41 77) . What is the gear ratio from this information?

 

[Philip]

Are there any more numbers on the tube? There should be either 7 or 8 letter/numbers. I can't tell you the ratio from the info posted. The available ratios in V8 models with an 8.5" were 2.56, 2.73 and 3.08. For I6 with the 7.5" was 2.73.

 

[big gear head]

My guess is that there is a 1 in front of that 6:41, which would make it 16:41, which is a 2.56 gear. Count the teeth on the ring gear and pinion gear. Divide the number on the ring gear by the number on the pinion gear, 41/16=2.56