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Post by jims442 on Dec 29, 2013 16:36:13 GMT -5
took my car to local gear shop to see about installing a possi unit i was told it needs to be a auburn unit not a eaton i know my way around cars and engines but not rear ends so what do you thing does auburn sound right
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Post by Big Mike on Dec 29, 2013 19:29:09 GMT -5
Would need some more info to make an informed opinion, what type of rear do you have in the car. Your shop must have said this because there wasn't an Eaton unit available for that rear end.
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Post by jims442 on Dec 29, 2013 21:43:07 GMT -5
i have a stock 65 rear end with 323 gears and a auto trans is one better eaton or auburn or does it matter
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Post by shane on Dec 29, 2013 22:47:58 GMT -5
I took a quick look in my jegs magazine they list the eaton posi unit for our cars with 3.36 gears and up. Maybe that's why your shop said auburn ? Just throwing a thought out there .
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Post by shane on Dec 29, 2013 23:16:48 GMT -5
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Post by jims442 on Dec 30, 2013 15:31:22 GMT -5
should one out of a 66 gto fit in my olds is it the same width and are 355 going to make me tach to hi on the freeway with a automatic
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Post by Big Mike on Dec 30, 2013 17:54:43 GMT -5
should one out of a 66 gto fit in my olds is it the same width and are 355 going to make me tach to hi on the freeway with a automatic That eBay rear will bolt up with no issues to your car. The 3.55 is a great ratio for both get up and go and on road use. Now if it was a 4:10 rear, that's a different story. |
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Post by RAM Z on Dec 30, 2013 18:04:42 GMT -5
66 rear end is either narrower or wider, google it. Its not the same as a 64-65. I just bought a 3.90 posi and ring gear set off ebay yesterday. Eaton style.
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Post by Big Mike on Dec 30, 2013 22:03:13 GMT -5
66 rear end is either narrower or wider, google it. Its not the same as a 64-65. It will still bolt up. Now you scared him off from trying. I put a posi rear end from a 1970 442 in my Cutlass Sports coupe. Yes, its a tad, and I mean a tad wider, but there were no clearance issues. You do have to jack the car up a bit higher to change the rear tires, but it's not a problem especially given the performance upgrade that you get. |
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Post by BR[] on Dec 31, 2013 7:34:00 GMT -5
This is the info I came up with years ago. I never heard of the 66 difference, so if you find any info on it, post it here so I can update the page.
Identifying GM 10-bolt Rearends:
From 1964-67, GM A-body rearend housing dimensions measure 56.5 inches, from flange to flange. Total measurements with the drums in place is 60.5 inches. The dimensions are similar to the 1967-69 Camaro / Firebird, and 1968-74 X-cars and clones, except leaf springs were used. 1968-72 rearend housings measure 58.5 inches from flange to flange, and with the brake drums in place, the total dimensions measure 62.5 inches. The dimensions are similar to the 1970-81 Camaro / Firebird, and 1975-79 X-cars and clones, except leaf springs were used.
The Oldsmobile 12-bolt has a 12 bolt cover and a 10 bolt gear, which measures 8.3".
Axle shafts are common to the housing used, and due to the usual characteristics like overall length and spline count, the shafts only interchange with the housing that is used. (e.g. 12 bolt shafts fit other 12-bolts, and 10 bolt shafts fit other 10-bolts.)
Rear spring mounting pads differed, in which 1964-66 rearends used a flat pad with a hole drilled in the center. 1968-72 rearends have circular spring mounting pads, which are 3/4" higher that the early flat pad.
1967 was a transition year, in which A-cars might have a 1964-66 style rearend, a 1968-72 rearend (which is wider and commonly available), or a "hybrid" rearend, which will have the 58.5" width, but with the early spring mounting pad and trailing arm brackets.
Rear upper control bushing eyes differ, and the positioning of the bushing eyes will differ. 1968-72 rearend housings will have a 3/8" forward positioning, which is farther that 1964-67 rearends.
1964 was the only year that the rearend bushing are small, and any upper trailing arm ( from any GM division ) will fit 1964 rearend housings
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Post by jims442 on Dec 31, 2013 8:18:39 GMT -5
thanks everyone for your input after much thought i've decided to have the local gear head put a new one in for around $750 sence a used one is about the same price so that makes more sence to me now i can leave 2 rubber marks down my street make my neighbors even happier HaHa
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Post by Deleted on Dec 31, 2013 11:49:59 GMT -5
thanks everyone for your input after much thought i've decided to have the local gear head put a new one in for around $750 sence a used one is about the same price so that makes more sence to me now i can leave 2 rubber marks down my street make my neighbors even happier HaHa The 66 transition is news to me also, had a few 66`s parted out both were same as 65, but it`s possible they were early builds. jims442, I read your quote above as your taking your gear builders advise and going Auburn? Smart move, better unit by far. Sometimes asking a question leads to more confusion, and 323`s are nice. If your still considering the 66 GTO housing with the deeper gears just ask for a flange to flange measurement, I`m guessing if it`s really a 66 rear housing it will be the same as yours. The deeper gears will affect your cruising rpm`s, your switch pitch will act differently. It will be quite a noticable difference without some modification to your switch on the accelerator linkage. |
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Post by oldstata on Dec 31, 2013 11:58:38 GMT -5
This is the info I came up with years ago. I never heard of the 66 difference, so if you find any info on it, post it here so I can update the page. Identifying GM 10-bolt Rearends: From 1964-67, GM A-body rearend housing dimensions measure 56.5 inches, from flange to flange. Total measurements with the drums in place is 60.5 inches. The dimensions are similar to the 1967-69 Camaro / Firebird, and 1968-74 X-cars and clones, except leaf springs were used. 1968-72 rearend housings measure 58.5 inches from flange to flange, and with the brake drums in place, the total dimensions measure 62.5 inches. The dimensions are similar to the 1970-81 Camaro / Firebird, and 1975-79 X-cars and clones, except leaf springs were used. The Oldsmobile 12-bolt has a 12 bolt cover and a 10 bolt gear, which measures 8.3". Axle shafts are common to the housing used, and due to the usual characteristics like overall length and spline count, the shafts only interchange with the housing that is used. (e.g. 12 bolt shafts fit other 12-bolts, and 10 bolt shafts fit other 10-bolts.) Rear spring mounting pads differed, in which 1964-66 rearends used a flat pad with a hole drilled in the center. 1968-72 rearends have circular spring mounting pads, which are 3/4" higher that the early flat pad. 1967 was a transition year, in which A-cars might have a 1964-66 style rearend, a 1968-72 rearend (which is wider and commonly available), or a "hybrid" rearend, which will have the 58.5" width, but with the early spring mounting pad and trailing arm brackets. Rear upper control bushing eyes differ, and the positioning of the bushing eyes will differ. 1968-72 rearend housings will have a 3/8" forward positioning, which is farther that 1964-67 rearends. 1964 was the only year that the rearend bushing are small, and any upper trailing arm ( from any GM division ) will fit 1964 rearend housings So I plan to drop a 70 olds 12 bolt in my 65 will I need the later springs or will the early 65 seeing work with the updated perch |
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Post by BR[] on Dec 31, 2013 13:21:20 GMT -5
it'll work, but it's a wider rear end an will limit the wheels that you can use. These cars are tight with the standard width rear end. You won't be able to run anything with much of a reverse.
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Post by Deleted on Dec 31, 2013 15:08:20 GMT -5
This is the info I came up with years ago. I never heard of the 66 difference, so if you find any info on it, post it here so I can update the page. Identifying GM 10-bolt Rearends: From 1964-67, GM A-body rearend housing dimensions measure 56.5 inches, from flange to flange. Total measurements with the drums in place is 60.5 inches. The dimensions are similar to the 1967-69 Camaro / Firebird, and 1968-74 X-cars and clones, except leaf springs were used. 1968-72 rearend housings measure 58.5 inches from flange to flange, and with the brake drums in place, the total dimensions measure 62.5 inches. The dimensions are similar to the 1970-81 Camaro / Firebird, and 1975-79 X-cars and clones, except leaf springs were used. The Oldsmobile 12-bolt has a 12 bolt cover and a 10 bolt gear, which measures 8.3". Axle shafts are common to the housing used, and due to the usual characteristics like overall length and spline count, the shafts only interchange with the housing that is used. (e.g. 12 bolt shafts fit other 12-bolts, and 10 bolt shafts fit other 10-bolts.) Rear spring mounting pads differed, in which 1964-66 rearends used a flat pad with a hole drilled in the center. 1968-72 rearends have circular spring mounting pads, which are 3/4" higher that the early flat pad. 1967 was a transition year, in which A-cars might have a 1964-66 style rearend, a 1968-72 rearend (which is wider and commonly available), or a "hybrid" rearend, which will have the 58.5" width, but with the early spring mounting pad and trailing arm brackets. Rear upper control bushing eyes differ, and the positioning of the bushing eyes will differ. 1968-72 rearend housings will have a 3/8" forward positioning, which is farther that 1964-67 rearends. 1964 was the only year that the rearend bushing are small, and any upper trailing arm ( from any GM division ) will fit 1964 rearend housings So I plan to drop a 70 olds 12 bolt in my 65 will I need the later springs or will the early 65 seeing work with the updated perch This would be my biggest concern, adjustable arms would be necessary. That, along with changing the over under steer characteristics would mean some geometry changes. Looks like at least a couple guys here need to bone up on repositioning a third member |
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Post by oldstata on Dec 31, 2013 15:42:27 GMT -5
Planned on adjustable upper arms already but have not heard this was going to be a issue main reason I was going adjustable is because I am installing a long tail th400 and didn't want my pinion angle off
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Post by RAM Z on Dec 31, 2013 17:16:02 GMT -5
Google is saying 64-67 is same width. I did read somewhere a 66 guy that said 66 was a tad wider but I cant find anything to confirm that.
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Post by Big Mike on Dec 31, 2013 19:53:52 GMT -5
Rear upper control bushing eyes differ, and the positioning of the bushing eyes will differ. 1968-72 rearend housings will have a 3/8" forward positioning, which is farther that 1964-67 rearends.This would be my biggest concern, adjustable arms would be necessary. That, along with changing the over under steer characteristics would mean some geometry changes. Looks like at least a couple guys here need to bone up on repositioning a third member I don't know, I installed the rear in my Cutlass in1981 and the car was a daily driver until 1990. Never had an issue. |
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Post by boba65442 on Jan 1, 2014 15:55:42 GMT -5
Bro thanks for the concise rear information. Very helpful.
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Post by rag on Jan 5, 2014 11:56:56 GMT -5
My 2 cents worth, Olds rears became wider in 1966, Pontiac rears became wider in 1967, but the difference is only 1" total so causes no problems. I put a '70 rear in my '65 442 years ago, no issues there either other than you can't use a wider or reverse wheel like Bro says.
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