I have a disk brake rear removed from a 5 speed 90 RS that I'm trying to identify. It is a 10 bolt, cast iron calipers, 10.5 inch rotor, limited slip. The code on the axle tube is 4 HY C293 1, casting number is 22522676. I think the code indicates the year as 1987 with limited slip 3.23 ratio and am trying to confirm whether this may have been available in 1990. Also, searching through other posts, it sounds like there is little good to say about the cast iron calipers and they were subject to recall. I have to make do with this rear axle assembly. Is there a replacement caliper that would work or would rebuilt replacements be okay? I need to stick with 15 inch wheels for now too. I have the proportioning valve,master cylinder and emergency brake cables from the donor 90 RS. Are there any other parts I need. Any and all suggestions welcome (except to dump this rear and start over LOL).

Thanks,
Mike

 

The rear is a pre-89 rearend as you mentioned. No '89-up disc rears got the old iron calipers so there's a start. Check the ratio and if you want to keep it just do a rear disc conversion to the newer aluminum caliper rear discs, it's an easy swap. Thing is that the cables from the '90 shouldn't fit your earlier car. If they do they must have been swapped along with the rearend. If you rebuild the calipers make sure you install the recall kit in them, you can't tell if replacements from the parts store will have that installed or not.

Ed

 

Thanks Ed,

I'm beginning to wonder whether the junkyard correctly identified the year of the donor car as a 90. I'll probably go back and check this weekend to be sure of the parts source. What is involved in swapping to the aluminum calipers? That is the route i'd prefer to go. Are there kits available? (Oh, I didn't specify in my original post, my car is a 1984 z28.)

Thanks again,
Mike