I'm helping a buddy swap out his 9 bolt rear in his 89 Iroc with 277's for a 89 rear with 345's. I noticed the rear that came out of his car had diff. backing plates. They'er zink coated without any dust shield tack welded to them. The backing plates on the rear that have the 345's are shaped different . They have dust shields spot welded to them but even without the shields in place they are shaped totally different.I know 89 was the only year that the 9 bolts had the aluminum calipers ,but two diff. rears made the same year with diff backing plates. What Gives?
Before someone asks yes both rears have the same calipers,rotors, caliper cradels,etc.Did someone at one time make aftermarket backing plates for 9 bolts with PBR brakes? Reason I'm asking is the ones without the dust shields have a gold/zink coating and are a little thicker metal than the dust shielded ones. And no none of the holes have been elongated on either set of backing plates.Any Ideas. Thanks

 

Correct. There's 2 types, one with and one without the dust shields. My '89 2.77 came with the dust shield type. They are both factory designs, but I have no idea what caused the difference.


Ed

 

The left one is from a 9-bolt without dust shield (and it was zinc coated). The other is the 10-bolt.

JamesC

 

Yes,I thought it was kinda odd, I wonder what determined weather you got dust shields or not.