Thread: 3.1 tranny on a 3.8?

id call a junkyard that can cross reference it before wasting money on something that doesnt work. i would have thought 3.1's had a 4t60e's. theres alot of factors that could make it not work at least without some work. we dont even know what the op's car is...such as SE,GT or GTP.

GP2002.. How do you know it's the same gear ratio? You listed out what looks like an HD trans with 33/37 tooth counts on drive/driven gears and didn't mention the FDR ratio. NonHD transmissions have a 35/35 tooth count on the drive/driven and differing FDR ratios based on the vehicle. In NA Bonnies 4T65E you can get 2.84 or 3.06 FDR's, All SC'd HD 4T65E's had a 3.29 FDR (when combined with the 33/37 it becomes 2.93)

In GP GT's there was a 3.29 diff in the non-hd trans.... I totally forget whats in the W body non-hd normally.