I bought a 72' 455 GS, and the guy I bought it from did not know a great deal about it, so he could not answer any of my questions about the build etc., on the car. By Taking Pictures of the bottom side of car I found the Axle tube stamped with (CI 0512 B), with a casting number of (NF 8894939), so from that I found that It apparently has a 12 bolt rear axle from a 67 Chevelle with a 3.73 posi in it. The guy that built this car also had put some aero-space components disc brakes all he way around but with no emergency brakes on the rear, and went with 17" rims all the way around. My Question being, What could can be done with this 67 Chevelle rear end to get the brakes and wheels back to 15" and with emergency brakes to boot ? Any information anyone you can give as to what brake parts could be installed to take care of my desire to get back to the 15" size and with emergency brake set-up that will work with this GS A Body set up would be greatly appreciated ? Can you install run of the mill Chevy rear brake components ? Or what might be the best approach with something like that ? Any advise would be greatly appreciated. Thank You. Bill
You can use rear drum brakes off of any GM A body 64-72, F body 67-probably 81, X body probably 68-74 and perhaps later. Doesn't much matter if it's a Chevy, Buick, Pontic or Olds, they're pretty much all the same.
That 12 bolt is worth some money. You could sell that and purchase the 71/72, 8.5, 10 bolt that would have been in originally. even have one built with a new eaton posi, moser axles & HD bolt in retainers (Chevy uses c-clips). Thats the rear end you should have in that car. just my opinion. EDIT: It may be a 70/71 8.5 A body Buick rearend. EDIT: Nope, I was right the first time 71/72
I imagine that 67' 12 bolt probably is worth some money, I don't have a clue how much, but I know the guy that owned this thing did put some money into it (wish I could have talked to him). It seemed like he was going for a pro touring look. He had purchased the touring springs(Eibach" 1" lowering special handling springs all the way around), "Aero-Space Components", disc brakes all the way around (But no Parking Brake on the rear), with 17" "Vintage Wheel Works" Rims all the way around. Tubular front suspension, Clean car, but dropping it 1", andthen going to 17" rims, leaves no room in the wheel well for turns the front. That's why I want to go back to 15" Rim size and regular stock springs, with a parking brake. Any ideas on how best to handle this would be greatly appreciated. Thanks for any input you can give me, I appreciate it. Thanks. Bill
I think you may want to re-read your edit. There is no such animal as a 70/71 8.5" A body rear end. You meant 71-72 I believe.
I can't say if it's a 67 rear or not, and I'm too lazy to check the numbers. But I'm 99.9% sure a 67 rear is a different width than later rears. I forget if it's wider or more narrow, but that may be why those plates are on the end of the axle tubes.
That plate on the end of the axle tube is a bracket for the brake caliper. That does look to be the narrower 12-bolt Chevy rear,but with the rear disc brakes,and the thicker rotor hats,the overall width is almost the same as the wider rear with factory drums. If you do convert that rear back to drums,you will need to pull the cover and remove the c-clips,to slide the axles out.This will allow you to remove the caliper brackets and install the drum brake backing plates. This will also bring your existing wheels onboard slightly,so make sure you have room. If you need some original 71-72 Buick trishield drums,I have some.
Are these swaps a bolt-in? I thought that '64 thru '67, '68 thru '72 and '73 thru '77 on all those A body styles were different widths.
yep, the 71/72 is wider then the 67 stock 8.2 but not by much. someone will know measurements and chime in. I boxed my lowers, added a sway bar. everything was pretty straight forward. this pic is with 15" rims
Not so on Olds A body. The F-85/Cutlass/442 uses a relatively narrow rear end in 1964-65 and a relatively wide rear end 1966-1972. The early narrow differentials are all 8.2" 10 bolts. The later wide differentials are 8.2" 10 bolts in 1966-1967, Type O 12 bolts 1968-1970, or Chevy 12 bolts of the same width if Oshawa built, and 8.5" 10 bolts for 1971-1972. 73-77 is also a 10 bolt with a unique wider width and shock mount locations different from the older A body.
I'll agree.... I have a narrow '64 Ols rear which is the same width as a '66 Chevelle 12 bolt I have. My 65-66 GS rears are about an inch wider. I've read conflicting info on whether the 68-up are wider than the 65-66 Buick. Your 12 bolt appears to have the original axle flanges so a stock 11" drum setup can be used. On my '66 12 bolt I put a 12" drum setup on from a '73-up GM intermediate..... Monte Carlo, Regal, etc. If you want rear discs there are aftermarket options. The early 80's Trans Am may swap. Chcek out Georges site for details: http://www.buickperformanceclub.com/page1.htm
So, '64 thru '72 (even though there are slight width differences) will interchange with no welding/relocating of mounting points? '73-'77 will not.
My 71 bolted right in. stock shocks and springs. the U-joint has a strap mount instead of the U-bolt. I changed my trans so I don't know about the stock driveshaft length fitting.
Correct. But some U joint & driveshaft mods may also be mandated by the differentials involved in the swap.
Thank You All for the clarification. I have a complete posi (never checked gear ratio) from a '76 with a sway bar. I was going to measure to see if just the bar would fit our '65 Skylark pervertible.
Yes, Thank You guys for the information, I greatly appreciate your input on that 12 bolt chevelle rear end. I did see somewhere on the internet, on a chevelle site, where the 1967 12 bolt rear end with the axle tube stamping "CI" and casting number "N3894939" is a narrower rear end than other chevelle rear ends from the 60's. This is what I saw on site for 1967 as follows: 12-Bolt Casting #N3894939 (narrow early model year), #NF3917124 (wide late model year)* 10-Bolt Casting #3894938N Bill
Now what those dimensions actually are for the 67' and the comparison to the Buick 8.5" Rear Axle? I'm not sure. Any one have any ideas ? Thanks. Bill
