I have an 85 Iroc-Z. I bought an Eaton posi unit with 3.73's and the 28 spline axles out of an 89 Iroc, but I have heard that they will not work in my housing because it is a 9 bolt instead of the 10? Please let me know if you know the facts, also let me know if there is a way to make it work. Thanks for the help!

Also if I were to buy a set of 3.73's for my car would I need to buy the "thick gears". Thanks again.

 

Well I give the short answer.....NO and again NO. Now the reason: BW 9-bolt & 10-bolt parts are NOT interchangeable. Nothing you bought will work in a BW 9-bolt.

 

Looks like you need to get a 10 bolt housing to put all of those parts in. Can you get the housing that the axles came from? A 10 bolt housing should be cheap, or free.

 

Is your rear end original? it should be a 10 bolt then shouldnt it? i thought 9 bolts were 87-89.

9 bolt parts will not work on 10 bolts and vice versa. Your original post confuses me a little bit because i dont know if you have a 10 bolt or a 9 bolt? Im assuming you have a 9 bolt but it sounds like you might be unsure.....


Assuming you have a 10 bolt, you can swap everything right in
Assuming you have a 9 bolt(which you would have had to put in yourself you cannot use the parts you have.

First find out what your car has. If its got 10 bolts, or 9 on the diff cover than its a 9 or 10 bolt.

 

Sorry for the confusion. I was meaning my rearend is a 10 bolt, the parts that I purchased are supposedly from a 9 bolt. The posi unit is an Eaton (10 bolts hold on the ring gearon), and it came with the 28 spline axles. Did they put eaton's in the 89's? Where are the size differences between the two rearends? Thanks.

 

The only thing the 10 bolt and 9 bolt have in common is that they both have the same mounting points to put them under a third gen. Internally, they are completely different diffs.

What you're asking is the same as asking if a ford 7.5 posi will fit into your GM 7.5 diff or asking if ford heads will fit on your chev block. They have nothing in common.

 

i was under the impression that there were no real aftermarket parts for the 9bolt. just stock replacement stuff like axles, posi, yadda yadda except the reinforcement cover is about the only performance upgrade available. if he sold u a eaton posi then its not out of a 9bolt. they have eaton posi's for 10bolts as well as auburns. pretty sure the only posi u can get for a 9bolt is a stock replacement. and its a cone style like the auburn=poop cuz the cones wear and put metal shavings etc into the case/fluid and are not rebuildable.

tell me if im mistaken

 

you are correct unless were both wrong lol. And gearing for a 9 bolt was 2.77 3.27 3.45 and 3.77 while 10 bolt gearing was 2.73 3.23 3.42 and 3.73...... are the axles different lengths?? because 9 bolt axles have one that is longer and one that is shorter while 10 bolt axles are the same size.

 

I've got an 83 Z-28 Crossfire Camaro. It has the stock rear end, which I believe is a 2.73. I got an offer to get some brand new 4.11 gears for third gen camaro for pretty cheap. Will these work? I'm kinda new to this stuff and I'd have a shop do the installation this spring. I just need to know if the swap is possible.

can anyone help me?

 

If they're compatible with a series II carrier, yes. Check the FAQ's About 10-bolts at the top of the page for more info.

JamesC