Rear differential troubles - Impala Tech
Transmission & Driveline Transmissions & Differentials

 
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post #1 of 9 (permalink) Old 06-03-2016, 09:20 PM Thread Starter
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Rear differential troubles

Well, I knew it was only a matter of time. Ripped the rearend apart on the 63 Impala wagon...468 turbo 400 will do it. Now what to do? What are my options? I don't have the $ to order up a built bolt in ford 9" " and would rather keep her at least all gm if possible. Ideas or opinions welcome, guidance appreciated! I have also always wondered how the heck those drag racing guys back in the early 60s kept the two piece driveshafts from self distructing? Help!!!
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post #2 of 9 (permalink) Old 06-03-2016, 10:45 PM
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Drop out Chevy rear ends were notoriously weak. Surprised it lasted as long as it did behind a high torque BBC. The rear end was designed to handle only the power of the 235 in line six as Chevy was the last in the GM line up to get their own V8 in 1955. It wasn't until the 327 came out in 1963 that rear ends started breaking under warranty. It wasn't until the rear end started to eat into GM profits that Chevy even thought about upgrading it or changing it out for another solution in 1965.

Place the Ford nine inch at the bottom of your replacement list. First off it isn't all that strong if you are talking about a stock Ford part. Only the high dollar aftermarket parts that are machined out of billet unobtainium are even close to being as strong as a Chevy 12 bolt, but there is still the problem of parasitic drag that makes a nine inch a poor choice. It is as strong as the Spicer ten bolt found under most 1965-72 cars as both shared the same 28 spline axle size.

First choice on your list should be a Pontiac-Olds rear end out of a 1957-63. It is nearly as bullet proof in it's pure stock form as is a Dana 60. It even looks stock as it uses a drop out center section. That style rear end was what I used under my old Chevy two door powered by a 409 (next weakest link I encountered after I stopped breaking rear ends, and universals), was the Borg Warner T-10 tranny.

Second rear end choice should be a Dana 60 out of a Ford tree quarter or a one ton pick-up cut down to fit with big Ford Torrino wheel bearings and aftermarket 35 spline axles. With the Ford wheel bearings you can choose between disc brakes off of a Ford Explorer or drum brakes off of a Ford SUV as both were made as a stock option.

If neither seems economical or obtainable (The Olds rear is scarce in wrecking yards as many people hoarded them or resale) your final choice should be a 12 bolt Spicer rear out of a 1965-72 Impala. In stock trim a Spicer made 12 bolt with it's 30 spline axles and nodular iron case were stronger than the cast iron pumpkin and 28 spline axles used in all stock nine inch applications. There were a few exceptions in the case of high horse cars with a BBF (427/428/429) CJ's and of course the SOHC engined cars and a few Boss 351 Cleveland Mustangs. Those high horse high torque muscle cars got the rare nodular iron case 31 spline axle differentials. But odds of finding one in a junk yards are slim to none.

Ford had so little faith in the stock 28 spline axled nine inches strength that they put Dana 60's under all of their F250/F350 and F450 pick-ups. Only the F100 and the F150 and their fleet of SUV's got the weaker 28 spline nine inch rears.

If you were building up a light Chevy truck or a mud buggy I would recommend the 14 bolt Chevy axle made by AAW as it is as strong as a Dana 80 rear end, but NHRA rule prohibit truck rear ends under any car in competition. The Dana 60 can be used because Chrysler chose that rear end for their Hemi equipped cars and those other cars that had their high horse 440 engines.

Big Dave
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post #3 of 9 (permalink) Old 06-04-2016, 11:35 AM Thread Starter
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Will the pldz Pontiac rear bolt in? If not, what work has to be done to fit it? I'm not a machinist but I do have friends that are"handy"...
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post #4 of 9 (permalink) Old 06-04-2016, 11:47 AM
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Quote:
Originally Posted by Nodak View Post
Will the pldz Pontiac rear bolt in? If not, what work has to be done to fit it? I'm not a machinist but I do have friends that are"handy"...
It isn't a bolt in but the lengths are the same and it uses the same drive shaft.

The Olds rear was leaf sprung while the Chevy used trailing arms and coil springs so brackets have to be carefully cut off the old and welded on the replacement rear end housing (keep welding moving from spot to spot to keep from warping the tubes).

Otherwise they are the same aside from the larger ring gear and bigger axles that the Olds rear used (that is why you have to swap housings instead of just the center section and axles).

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post #5 of 9 (permalink) Old 06-06-2016, 11:10 AM Thread Starter
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I have found a 1970 Oldsmobile Delta 88, equipped with a turbo 400 tranny, motor is gone. Is this diff a worthy candidate?
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post #6 of 9 (permalink) Old 06-06-2016, 01:29 PM
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In 1970 it will be a ten bolt or a 12 bolt rear end. Olds had a weird proprietary ten bolt made just for them; that didn't use a C-clip to hold the 28 spline axles in place. But because it is a weird Olds only part there is very limited gear choices and any regular Spicer ten bolt differential or ring and pinion gear sets will not fit in the housing that had 12 bolts holding the inspection plate in place (I bough a few of these thinking I was getting a 12 bolt rear but it turned out to be a 10 bolt I couldn't use). May still have one out in my rust pile in the barn.

Here is a car mag article explaining the olds rear end:

1957-1964 Pontiac and Oldsmobile Rearends - Street Rodder Magazine

Big Dave
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post #7 of 9 (permalink) Old 06-07-2016, 11:25 AM Thread Starter
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Great read on the p/o rear ends Dave! Thanks . Now it's time to roll up the sleeves and start the search...
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post #8 of 9 (permalink) Old 06-08-2016, 11:50 AM Thread Starter
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Would a 69 Buick posi diff be.any good? What should a guy expect to pay for such a unit, generally speaking of course...
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post #9 of 9 (permalink) Old 06-08-2016, 01:32 PM
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GM abandoned the Salisbury style rear end in 1965 to contract with Spicer (a subsidiary of Eaton-Dana) to supply the rear ends for all of their cars starting in 1965. As I mentioned Olds had their own idea as to what the specification should be retaining the press on axle bearing and 28 spline axle of the Chevy drop out rear end but using their own gear sets instead of the ones designed to work in the Spicer ten bolt (which is a slightly modified Dana 30 differential). I have no idea why they did this as the Pont-Olds rear end was bigger and stronger than the Spicer 12 bolt and didn't use a half of a washer (C-clip) to hold the axles in place. One can only assume it was cheaper and thus maximized the bonus check's going into the pockets of the board members.


I do not know if the Buick rear end is different from the Spicer used in the Chevy, but in every case it will not be a bolt in as the brackets arte going to be different. Here is a person selling the Olds "12 bolt" that has an 8.5 inch ring gear when the rest of the Spicer rear s used an 8.2 inch just like your car used only in a stronger housing:


Oldsmobile 12 Bolt 442 Cutlass Rear End Complete CFD 8 402221 AB Olds | eBay


Here is someone selling a complete Olds 9.3 inch rear end with coil overs and ladder bars ready to go under a drag car (you do not want ladder bars on the street as the suspension will bind):


Gasser Rear End Rearend 57 64 Pontiac Olds 4 56 Posi Ladder Bars Rat Rod | eBay


Here is someone selling center section leaving you in need of a housing and axles:


57 58 60 61 62 63 64 Olds Pontiac Center Section 3 42 Rearend Gears | eBay


Here is a complete rear end that has been narrowed to allow for wider tires in the rear, or to fit under an early Nova at a reasonable price:


1963 64 Olds Pontiac Rear End Axle 1933 41 Willys 1955 57 Chevy Gasser Nova | eBay


You can find lots of rears in different states of usefulness to you for a substitute rear end. You know your budget. You can find ten bolt spicer rear ends for the price of scrap metal. This is because no one wants one. They have the same 28 spline axles you have now and the same size 8.2 inch ring gear diameter. The only improvement is in a stronger nodular iron cast case with fitted axles plug welded into the differential case making it stiffer than your welded together collection of stamped steel parts made out of thin gage metal. The 12 bolt used a 8-7/8th inch ring gear and 30 spline axles (you can buy 31 spline axles to match a special 31 spline posi-traction differential sold by Moser to exceed the strength of a nine inch rear). Why do I keep mentioning the spline count of the axles? This is because the more splines on the axle the larger in diameter the axle is and thus the stronger it is.





Here is a Dana 60 vs a nine inch 31pline axle:





Dave Veitch
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