My '89 Iroc-Z convertible has rear disc brakes and does not have the J65 RPO code. How can I tell what rear end is under the car & if it came 4WD's?

 

All 82-92 four-wheel disc cars have the same RPO, J65. 82-88 cars are equipped with 10.5" rotors and Delco-Moraine iron calipers. 89-92 have the so-called performance and/or 1LE 11.7" rotors and PBR alum calipers.

RPO J42 = alum drums
RPO J41 = cast iron drums

JamesC

 

Count the bolts on the rear end cover. 9 bolt is Australian with aluminum PBR brake calipers. Some had delco-Moraine iron calipers. I installed an Auzzie 9 bolt with PBR's from a 89 IROC. Click on my Signature link below to see if yours looks like mine.

 

If it doesn't have J65, it didn't come with rear discs.

You can tell what rear is under the car by LOOKING AT THE PARTS.

Take off the cover; count the bolts; if there's 10, it's a 10-bolt, but if there's 9, ... you do the math. Then count teeth on the gears, that'll tell you the ratio. Look in the carrier, that'll tell you if it's posi or not. Pull an axle, that'll tell you how many splines your axles have. Takes about 5 minutes to find all that out; longer to jack up the car, and probably longer than you've sat there waiting for somebody to tell you what you've got and be wrong, than to determine all that stuff for yourself.

LOOK at the brakes. If they're iron, .... they're the iron garbage ones. If they're aluminum, they're PBRs.

Did I mention, the best way to IDENTIFY stuff, is to LOOK AT IT. Posting on the Internet only takes you just so far; after that, ya actually gotta get up off yer keyboard and do some "real" WORK. Not much, mind you, but at least a little.

 

There is a RPO J50 on console sticker.

 

So, what parts did you see when you LOOKED AT THE PARTS?

 

Originally equipped with drums.

JamesC

 

Thanx for info.
Will do that in A.M., but one needs to know what they are looking for..don't they?

 

Just finished checking out the rear end in my car.....it's a 9 bolt w/stock type panhard bar. The calipers are PBR's. It also has a alum. drive shaft and 36/24mm sway bars. I'm fairly sure that a alot of it didn't come with the car. Thanks for info EVERYONE!

 

does the VIN number on the SPID/RPO sticker match the car? the console may have been changed, hench the wrong rpos's

 

Yes, the VIN & console sticker match. I've come to the conclusion that a previous owner has done alot of swapping. The car has 350 instead of the 305 and also has SLP injectors, chip, and camshaft. It's a project car for my grandson & I to spend time together while rehabing and for him to learn how to work on cars. Thanks again for your help!

 

That's the thing with these old cars. All of the factory "codes" are no longer particularly raliable, due to the inevitable swappage that has gone on throughout all these decades between then and now.

We can helo you alot more with questions like "what parts do I buy" when you can tell us WHAT YOU'VE ACTAULLY GO NOW, than trying to "guess" off of the old facory "codes" that may or may not tell what's REALLY in the car NOW or not.

Needless to say, it helps to keep a record of what you find installed in the car. You may find that you need to buy spark plugs for a 69 Chevelle, valve cover gaskets for a 2000 Silverado, brake pads for a 94 Z28, and so on, rather than whatever your "codes" call for.

 

Right now we're just trying to figure out what we have, and to see what we need to make a reliable driver. To do that we need to solve three problems for now.

1) The drivers side rear disc won't come off ( I think the parking brake is frozen. ) Probably will require pulling the axle.

2) The exhaust cross over under the motor is touching the oil pan. Obvious fix here.

3) It's very hard to start when cold. When warm it runs great! FP is 43 psi w/regulator unplugged and no obvious vaccum leaks.

I'm good with old school mechanics and race car stuff, just not familiar with later model or computer stuff. I just purchased a factory service manual for it, hopefully that will help a bunch when it arrives. Again, Thanks so much for your help!