Ok I have a couple questions that I am sure you guys can help me with....... I bought a used rear end, 68-70 casting numbers, told it was a 3.42 factory posi out of a 69 GS. turns out it is a factory posi but it is a 2.92 ring and pinion. 41-14 teeth. the guy I bought it from feels terrible and I believe that he honestly thought it was a 3.42, my fault for not doing my due diligence. So I am looking at changing the ratio, possibly, but I am getting more confused the deeper I look into it. I spoke with Dave at FabCraft in Texas, he manufactures new 3.42 and 3.64 gear sets as well as the posi carriers. He is telling me that the carriers are different from 3.36 ratio up, so if I bought a new 3.42 ring gear it will not work with my carrier. Is this true? What would be different about it? He told me I would need some type of spacer plate to make it work, or a new carrier..... If this is all true then I would either go with maybe a 3.23 ratio or just cut my losses and try to sell the 2.92 posi. What are your thoughts on this? My car is a driver and I do run the highway quite a bit.
You can't use a 3.23 either, the carrier breaks are, 2.56 / 2.73-2.93 / 3.23-3.42 / 3.64- up. You should be able to use a spacer. Jim (Monzaz on V8) should be able to help you. PM him here, or just call him. His website is, http://jdrace.com/diff_id/10bBOP_Buick.htm http://jdrace.com/contact/contact.htm
just so I understand then, the bolt pattern is the same on all the ring gears, the difference is that I need the spacer to achieve proper back lash? correct? so the way I picture it is that my carrier ring gear mounting surface is cut deeper than one for a 3.42 ring.
I wouldn't put it exactly that way, but the dimensions of the 2, 3, and 4 series carriers are such that you need a spacer to use higher numerical ratio gear sets with lower series carriers. I didn't know that you could use an 8.5 spacer in an 8.2 rear, but Brian knows his stuff.
yes, Brian is the man! he has been helping me tremendously. he has a show quality 8.2 3.23 posi rear for sale on Ebay for a more than fair price. Money is just real tight for me right now.....
Yes,that is the spacer. Motive also makes one,#085050. This works because the 8.5" 10-bolt has the same inner diameter and bolt circle as the Buick ring gear. The difference in the series of carriers is the position of the ring gear flange. The numerically lower gears have a larger pinion head,so the ring gear/flange are farther to the left. The numerically higher gears have a smaller pinion head,so the ring gear/flange are farther to the right,or closer to the center. Since your car currently has a 2:56,you might want to try that 2:92,and see what you think.
for all the more it takes, and since I do have the unit I think I will take your advice and throw it in, see how she feels. Do you think it will make a noticeable difference? Thank you for all the help Brian.
I think there is enough of a gap in the ratio that you will notice something. If it were closer,like 2:73 to 2:92,you might not feel much of anything. Do you know for sure that your existing rear is 2:56? If it is,then I say go for it.
For a street cruiser...the existing set-up/2.92 will work fine. Don't forget to change your speedo driven gear in the trans...otherwise your speedo will be incorrect.
Any chance he's still got it for sale? If so can you throw up the link if didn't end up grabbing it. I'm Looking to put 3.36 gears in my rear but need a series 3 carrier. But for the cost of the rebuild and conversion I would be interested in the whole rear if it was refinished
I had the rear on here,completely restored,show-piece,for $1200.00. I didn't get much interest,so I put it on eBay. The winner bought it for a Cutlass.
Damn, I missed out, I started drooling when I read this thread and though it might still be available.
I am not a huge fan of ring gear spacers. The carrier breaks are for the reason previously mention about the pinion gear sizes. But u had a 8.5 that was a 2.9x gear from factory, ran a 4.10 and mini spool for about 10 yes drag racing. It took alot more shim on one side than than the other but did work. I am not sure I could gad gone any more. The funny thing is when you buy a full spool.....they never mention anything about ratio breaks and they have no clue what gear your going to put on them.......I would bet if your only going from a 2.9x to a mid 3. You could just shim it and get it to fit. Might have to buy an extra set of shims. Cause you will need thicker on one side and a good selection of thinner on the other.
I know what you mean. the more I started looking into building my rear, I could just buy the one from Brian. I would have jumped all over it but funds are tight right now. Im sure he would build what you want for a fair price tho? He is very knowledgeable on these BOP rears.
