According to the Tech Data on the main page to this site, GM stopped putting Borg Warner rears in our cars in 1990. As I was jacking up the car to put in the torque arm, I noticed Borg Warner stamped on the bottom of the differential casing, and a tag saying that it's part # 10142076 and a 3.27 ratio.

Did any 90 Irocs leave the factory with this rear in it, or did someone probably replace the old unit with this one? I have G92 on the RPO sticker, so I know I'm supposed to at least have a 3.23 posi.

Now.. is this rear supposed to be stronger/better than the rear I'm supposed to have? If I start ordering gears/brakes/etc... are the parts going to be different?

Thanks.

 

Yes, the 9 bolt is much stronger than the 10 bolt and yes the parts are different. The 9 bolt parts are more expensive. For a complete list of what is available, check my page at www.9bolt.com

Miles
9bolt.com

 

I had a 90 Iroc with a 9bolt.

 

I wonder if they were using up left over inventory, because I have always heard that they stoped making them in 89. Maybe they did continue to 90, I dont know.

Ben

 

That's what I was thinking. Is there a way to tell at what time of year the car was manufactured? VW Bugs have it on a tag in the trunk, wonder if GM does the same somewhere.

 

Don't forget warranty replacement. If someone's rear went out the dealer might have replaced it with a BW.

FWIW, I bought my 90 new and my rear end was replaced at 30k miles with a BW unit. I honestly don't know if it originally had a 10 bolt or 9 bolt. Too many years ago.

 

Maybe they put the stronger rears back in so that they wouldnt have to do it again.

Ben

 

How can I tell which series carrier is in the 9-bolt 3.27 BW Posi rear in my '87 IROC?

If it's a series I or II, is it upgradeable to a series III?

What's the diference with the series III?

Thanks for any help.

 

Synapsis,

About the Edelbrock torque arm and the need to modify it: As you may recall, I ordered one as well, so I was concerned about the fit after your experience. I phoned Edelbrock and was told that the arm would fit all 84-00 (?) cars, 'except' those with B/W rear ends.

JamesC

 

Why is this though,since the stock 10 bolt arm bolts right to the BW rear also?

 

Synapsis and I discussed this on another thread, in which we both posted pictures of the two arms. The stock arm is slightly curved where it attaches to the rear end, while the Edelbrock version is completely flat.

JamesC

 

*Now* I find this out.

I've cut a large portion of the "E" plate out, leaving around 1/2 inch of it at the welds for strength. I'm going to have someone weld a piece of strong tubing to the end that I cut, probably not necessary since the differential housing itself provides a lot of strength at that point.

Thanks for the info JamesC.

 

Check the edge of the driver side door, just below the latch. There should be a manufacurer's tag with the production date on it.

Eric

 

Series 3 carriers will work with gear ratios from 3.27 to 4.10, hence, you should have a series 3 carrier.

Miles
www.9bolt.com