I dropped off the 2NABOT this morning to get the rear end carrier swapped out for a posi carrier I found at a junkyard. My axle is a 1971 Buick 8.5 inch, non-C-clip-type, 3.08 open rear end. The donor was a '73 Chevy Caprice, C-clip-type, 2-something posi rear end. I pulled the c-clip carrier, got new clutches, shims, etc, and asked the best rear-end shop in town to do the swap. ** They just called, and said that they didn't think they'd be able to do it, because the c-clip carrier won't work in the BOP axle housing. He said he'd tried it before, and couldn't get the backlash set right, and didn't want to waste my time/money. Is that right? I thought it wouldn't make a difference, since my axles are held in at the wheel ends. If it *will* in fact swap out, should I try and get the shop to go ahead, and if so, what's a tactful way to do that? HELP!!!
Carrier swap. Was the 73 caprice a 8.5 rear...? If so it should work ok are the carrier bearings the same size as the other one...? They should be able to shim in the correct backlash with no problem. I have a 28 spline bolt in axle 8.5 rear and had swap to a 3 series carrier from a chevelle and it worked fine. I think it was from a 8.5 c clip style rear. Maybe somebody will chime in with more info. Billy.
Yup, both carriers are GM 8.5 inch. I'm thinking of having them put the new clutches in the posi carrier, and taking a shot at the carrier swap myself. I've got a chassis manual and a dial indicator for checking backlash, and think I can handle it. I'd really rather have a pro do it, though....but if the pro is misinformed, then???
Contact oPh in this board - he's the expert. I don't think it will work either, there is BOP corporate and then there's Chevy, but that is a feeling.... - Bill
The reason it won't work is you a 2 series carrier and 3 series gear. You will need a spacer plate to use 3 series gears on a 2 series carrier. You can get them from Jegs or Summit for $30. You will have to use another set of ring gear screws/bolts. OpH states he uses Chevy head washers and some other screws but I can not remember what they were. You need longer screws because the spacer plate is 3/16-1/4" and you lose thread engagement if you use the stock/original ring gear screws.
George - I don't think they'd be different series carriers, the 3-series went from 2.7-something up to 3.23, I'm dealing with a 2.93 or .97 (I forget) and a 3.08. At least, that's the info I've gotten from this board and 2 parts sources... o No: At any rate, I've emailed OpH (Roger), and he's sure the swap would work, he says he's done bazillions of them. Here's the latest info I just emailed him back, what do you guys think? ------------------------------- This has become a frustrating deal...as I said, the only shop anybody around here recommends thinks it won't work (I think he tried it with a different series carrier, that's why he couldn't get the backlash set), and so he recommended I call Randy's Ring and Pinion to get an Eaton (another $500, yuck). So I got the bright idea to call Randy's and see if they wouldn't clear it up, thinking that if they'd say it would fit, the mechanic would at least go along and try it. Only thing is, Opie (his real name) at Randy's said it wouldn't fit, since they're "completely different carriers". Opie than proceeded to tell me that it's not an 8.5, but an 8.2 inch rear in my '71 Buick, and the only thing available would be an Auburn posi. AAAARRRGH!!! I give up on these "pros" - Looks like I'll be doing the swap in my driveway with my chassis manual, dial indicator, and hand tools. From what I understand, the Main thing is to check the backlash (ring gear / carrier left-right location), and shim the "new" carrier to the same specs, right? How about carrier bearing preload, just follow the chassis manual? Also, what's involved in putting new posi clutches into the carrier and shimming them up (S-spring)? My Buick book doesn't cover that. The local shop will do it for $60, but... --------------------------------------- Like I said: AAAARRRRRGGGHHHHHHH!!!!! :rant: :af: :spank: :blast:
If you have the GM posi unit (has the S-spring), real easy to ID which you have. 1. 2 series, 2.41-2.56, carrier has part number 410409 and 3 large 9's cast onto the housing. 2. 3 series, 2.73-3.90, carrier has part number 410408 and 4 large 8's cast onto the housing. Once you confirm what you have, we can be more specific. 8.5" rears use 4 screws and 2 straps to hold the rear u-joint in place 8.2" rears use 2 U-bolts. Now, you can determine what you have and what you need to get the job done.
James, If the Caprice 8.5 carrier held 2.73 or 2.93 8.5 gears, it'll fit. 2.93 is a real odd 8.5 ratio... the only 2.93 8.5 gears I've ever found were in Buicks. Oddly enough there is demand for decent used 8.5 2.93 gearsets. In the past I've set-up 2 sets in 8.5 rears that owners were running Richmond 5 speeds. 2.93 gave a great 1-1 top gear ratio. Reference to the 8.5 ring gear spacers... one should use the Mr Gasket small block chevy headbolt washers with the special bolts that come with the Mr Gasket & Summit 8.5 ring gear spacer kits. Otherwise these special bolts will bottom out & strip the last 2-3 threads on the bolts. Being LH thread, there really is no alternatives in a slightly shorter bolt. Shimming up the clutchs... Basically need to pull the carrier apart, ck the thick clutch shim on each side, then start with .002 thicker on each side.That is taking into account that carrier has a lot of miles on it & you want a tight posi. Will ck back in. Roger
OK, the donor ring gear (which I'm not going to use, I like my 3.08 gears) is physically 8.5 inches across, and stamped: | GM 3984825 15 41 3 73 so that's a 2.73, not 2.93 like I thought. ou: The donor posi carrier has the following numbers cast on the end: 410408N GM 4 opposite that is cast: C14 There are no large 8's or 9's anywhere on the carrier. o No: Also, there were 4 screws and 2 straps to hold the rear u-joint in place.
James, the 8.5 posi carrier you're showing in the pic is definitely the low ratio version. The original one out of my '73 T/A is same casting number. The four #8's or #9's cast on the rh end of the corpoate 8.5 posi carriers did not come about till some time around '75 production. '76 def had the big #8's or #9's on the end. Back in the late 80's & through the 90's, before rebuilding the #8 & #9 posi carriers, I used to grind the #8 & #9's & the #48xxxx numbers off & heavily shotblast the bare posi cases. Made the posis hard to ID in rears we were building. Have also ground a ton of the lower casting lugs off the most popular 8.5 housings :grin: :3gears: Roger
I'm getting cornfused - by "low ratio", you mean higher numeric, right? This is the same series as my Buick 3.08 carrier, isn't it? Bottom line, this carrier will work in my axle, correct? Man, that's just sneaky! I like it. :Brow:
James, Yes your posi will fit. Feel free & drop me an e-mail when you get the carrier disassembled. Roger
