What Rear End Do I Have??

[87GrandPrix]

I counted 10 bolts, It's Posi.

 

[Blake442]

7.5"

 

[87GrandPrix]

Thanks, Do you know what the gear ratio of that would be?

 

[schoust]

Nah he wouldn't be able to answer that question for you. But you can answer this yourself be looking to the Vin tag for your info. I believe that all of the information lies in the VIN? Then again I still do not know what my rear is in my El Camino Lol?? No matter though because I know without a doubt that it is far lighter than what I need for what I am needing Lol!.................

 

[DRIVEN]

Thanks, Do you know what the gear ratio of that would be?

Jack up the rear. Put it in neutral. Put a mark on one or both tires. Rotate the driveline by hand. Gear ratio is the number if times the driveline spins. Example; 3 1/4 rotations is 3.25:1 ratio.

 

[Blake442]

It's even easier to look at the RPO label under the trunk lid.

 

[DRIVEN]

If I was as smart as I am pretty, I might have suggested that. My car doesn't have that.

 

[Blake442]

Yeah, they're only on '84-up cars...

Just make sure the VIN on the RPO label matches your car, since depending on the cars history, the trunk lid could have been swapped.

 

[schoust]

Curious Blake how do you read that thing? What numbers are the rear end??

 

[Blake442]

The rear end codes start with G.

Here's the common G-body rear end related codes...
GH2-2.29 ratio
GM8-2.56 ratio
GT4-3.73 ratio
GU1-2.41 ratio
GU2-2.73 ratio
GU4-3.08 ratio
GU5-3.23 ratio
G72-2.14 ratio

G80-limited slip differential

G87-8.5in 10 bolt axle
G89-7.5in 10 bolt axle

Here's a fun site to look at...
http://www.c2e.info/rpocodes/