i have an 89 iroc with a 5-speed manual, it originally had the 305 tuneport, i was wondering the specifics on the tranny and rearend, i have found some information that says the rearend is a borg-warner 3.45 but i'm not positive that is right, can someone help me out and let me know where i can find the information, thank you in advance

 

The tranny is a Borg Warner T5.

The rear end is probably a Borg Warner 9 bolt with 3.45 gears and PBR brakes.

Get under the back of the car, if the cover on the differential has a rubber plug in it, then its a BW. If the car was originally a LB9 5 spd its most likely a 3.45 rear end. If you really have to know, you can check your RPO codes in the console, or you can pull the cover and look at the ring gear. It'll have the ratio stamped in it.

 

Couldnt it be a 3.08 rear though if he has single cats? 3.45 if he has dual cats?

 

good point!! i just saw that on the tech date the 10 hp increase was the n10 option (dual cats) and apparentely they came with the 3.45's bw...

https://www.thirdgen.org/newdesign/tech/techdb.shtml

 

Easiest place to fnd the information about what's inside the rear end, is inside the rear end. Take off the cover and look.

Have you changed the fluid in it lately? Then it needs it. While you're doing the overdue maintenance, look at the gears. Count the teeth, or at least look at the stamping around the edge of the ring gear.

 

You really can't miss the ratio stamp on a 9 bolt. If it is a 9 bolt there's no need to count the teeth.

 

my Formula's 9-bolt has what i like to call a "toe tag". it has two tags on the rear end cover. one says spin resistant-add only approved lubricant. the other tells me a serial number and a RATIO. i have 3.27's


Josh