I have an '86 IROC-Z/Z-28 Camaro with disc rear brakes and a the 305 motor with 700r4 tranny. What RPO code am I looking for to tell me the ratio or what possibilities for rear gearing are there in this diff? Thanks.

 

Look at RPO codes that start with G.

Those will tell you WHAT THE CAR CAME WITH; but not necessarily WHAT'S IN IT NOW. Lots of people "think" "assume" "were told" "are sure" their rear is the original, but then find out the hard way (buying $$$$$$ parts that don't fit) that it isn't.

Advice: screw the codes. Pull the cover and look at it.

Changed the fluid lately?

I though not. While you're catching up on the overdue maintenance that you've been putting off, make a point of looking at the gears.

And, inspect the carrier too, so we're all spared yet another annoying redundant pointless "do I have posi" post.

 

Hehe, I'm not that noob...I can figure out the posi part :-p I am positive this is the original rear diff. but this isn't a car that I am driving per se. I was planning on possibly parting it out and was just curious how to go about finding the ratio, assuming it's stock still, without pulling anything, counting gears, or looking for a rusted out tab that hasn't been on the car for probably 10 years now :-) I will locate the "G" codes and see what they are and go from there. If it came originally with an undesirable rear end, I will probably leave it in the car rather than go through the trouble of removing the axle to maybe get someone to get it out of my yard for free. Thanks for the code info and I will grab that number and see what it says.

 

Alright, I've got a GC5 GC6 GU5 G80. Thanks.

 

G80 = Limited Slip differential
GU5 = 3.23 ratio, 13:42 tooth comb.

GC5 and GC6 give error codes on the RPO decoder I have from the TGO home page, so I am not sure what they are

Dave

 

Thanks. I couldn't get that decoder to load to my computer. I found this morning that the GC5 & GC6 were some kind of bumper/body height option codes. Whatever that means.