Joined: Jun 2009

Posts: 396

Likes: 3

From: California

Car: 1991 Pontiac Firebird

Engine: 355 TBI

Transmission: 7004R

Axle/Gears: 3.27/42 ?

Hi everyone!

I just got my 700R4 tail housing cover off and noticed I have a red drive and driven gear. Everything seemed fine until I compared the new driven gear (black) with the original (red) and noticed that my new black driven gear is larger than the stock red one. Not by a lot but it’s noticeable.

Anyone know if this is okay?

Here is my setup:
1991 Base Firebird w/ Auto 700R4
3.42 gears
275/40-17 on 17x9 wheels
New drive gear number 8642620 (gray, 15 teeth)
New driven gear number 25513047 (black, 40 teeth)

I used this sticky to figure out what I needed as far as the new parts go:
https://www.thirdgen.org/forums/tran...eedometer.html

I heard of people breaking gears due to improper combos so just want to make sure I’m doing the right thing and the size differences are okay.