f-85

Hey Guys

Blew my rear at the Byron BOP race. Broke the pinion shaft clean off right within the seal of the rear. And Dropped my driveshaft at the line. My car did run good though. 12.89 at 106.48 on street tires and a 2.78 rear through the mufflers. So anyway my question is what rear ends can i just bolt it. I wanna drive my car some more before winter. Im a broke *** right now so the more options i have the better.

joe_padavano

Nice runs. The easy bolt-in is any 64-67 A-body axle. The 68-72 axles will bolt in but besides the slightly wider flange-to-flange dimension, you also have the issue of rear springs. The later axles (which actually includes the 67 Type O) have different lower spring perches that require the matching springs.

f-85

Hey Joe

Thanks for the reply. So if i went with a 68-72 or O type i would have to get the 68-72 springs then? I really dont want to go all out with this car. Its just my daily driver. I want to build a street/strip 64-65 sometime soon. And thats the car i can put all the extra work into. Im just trying to find a good option for car,if only temp so i can drive it this fall. I can work on mybe rebuilding my rear over the winter for my 64. Im just not ready to park it yet. Slow olds was nice enough to give me a 66 Chevy 3.08 open rear. But it has a bad axle and is gonna need the brakes all redone. Maybe that will be my best option.

joe_padavano

Yes, the early axles have a flat spring perch. The bottom of the spring is full diameter. The later axles have a raised spring perch and the bottom of the spring is reduced diameter.

You should be able to swap your brakes onto the other axle. In fact, the easy way to swap axles without bleeding brakes is to pull the axle shafts, unbolt the backing plates, and hang them from the frame. Swap the brake-less axles, reattach the backing plates, and reinstall the axle shafts.

f-85

Hey Joe

Yeah i pulled my rear and had a nightmare getting the old axles out. I got the backing plates hanging. I redid all my brakes completly with the last year or so. But i dont think the backing plates are the same from my rear to the 66 chevy. Im going over to Jeremys (Jchicago) now to put that chevy rear back together. Ill just rock the bad axle for the last 2 motnhs and take it easy on it. Then over the winter ill find a permenant setup. Jeremy just called and said to trace out the flange to see if it might fit. But if you know for sure. Just post here and ill look when i get over to his place. Thanks again for the info.


Josh

joe_padavano

They should be, or should at least be interchangeable.

monzaz

All the backing plate interchange...Only exception would be wagon backing plates. They have 2.5" wide drums & shoes.

The reason the rear pinion poped was because it was a stock cast gear. BAck in the day the gears and most metal was not a good mix of premium metal...Believe it or not the new stuff is better even from korea china etc....lol.

Buy a good new set and keep that rear. She will do the job.

The very early 1964 1965 old rears are pretty narrow...you might have some issues with a 68-72 the 66 67 might be fine Pontiac went larger in 67 just like the 68-72....The BOP axles have 3 different wides 64 65 66 6768 69 70 71 72. I think the Pontiac increased width sooner than the Buick and olds rear because of the wide track commercial etc. I always thought 64-67 were the same too...then I had crazy number matching guys call and bring shop manual and actual measuring with all rears side by side proved that truely there are 3 different widths through the 1964-1972 a-body cars.

so 1964-1966 BOP should all work quite well
1964-1967 chevy will also fit the bill
68-72 will work but watch the width


Spring perches- You should not have an issue with just popping the springs onto the 67-72 raise spring perch pad...I will double check this for sure in 5 minutes. Jim

joe_padavano

The 1967 and 1968 Type O housings carry the same part number in the factory parts book, implying that they are the same width.

f-85

Well i did it all. I put in the 66 Chevy rear. Ordered up a minispool for it (i just couldnt go to a peg leg after having the posi) I know its not the best for street, but i only need it to last 2 months LOL

The reason the rear broke is the posi let loos. The springs washers, and pit where all broke. Must have bound up and thats what sheered the pinion. Heres a few pics.

monzaz

Any pictures of the posi gears and case parts?? Let me know if anything is left parts is parts to us...we recondition old units for guys that want there original posi units for show...they do not necessarly need to hold up to racing. Is any thing left at all? PM me maybe we can work out something. Even springs help.

I see that alot with the chevy 25 spline pinions they just snap right behind the spline cut. FActory gears will do that. Sometimes the pinion gear head will 1/4 itself too I have seen bad casting on them too.

Good luck with it and watch the axles next with the mini spool. Jim

f-85

Hey Jim

Heres some pics of the carrier, and springs. If you want i can take the carrier apart. The ring gear is good. But the pinion is broke right behind the spline at the step. Must just have been a weak point. Heres a few pics. Ill also take the carrier apart and see how it looks on the inside.

Josh

f-85

Hey Jim

Here are the pics. Looks like the small spider gears are bad. The bigger ones are ok.

Run to Rund

64-66 rear coils are full diameter at the top, pigtail at the bottom. 67-72 are pigtail at both ends. Up to 67, the bottom spring perch was flat with a contoured retainer and a through bolt; 68-72 used a cup retainer but the springs are functionally the same at the bottom. You can use your 1964 springs with a 68 up rear end without any problem.

monzaz

If you look in the case on both sides you can see the round towers where the cone base has bottomed out. This will cause heat to build and the posi NOT to hook up...It will just spin on this tower and heat up the unit...then the spiders will weld to the cross shaft causing it to sieze up and then something will give which it did...OOOpps. STUFF HAPPENS. The unit was just old and used up. Nothing you could have done but NOT to race or drive it. THAT ain't gonna happen ...RIGHT! RAce, RACE, race...

Jim

f-85

Hey Jim

Well my posi worked great up until this year. Then it just started slipping. Probaby the brake torques. I need to get a line lock. I know SH*T happens. It was still cool. this was the first time my car was in the 12s. So i was happy about that. It didnt bother me that bad about the rear blowing. I was just real happy the car did what it did. Its just my driver, i only take it to the track alittle. I sent you a pm.


Josh

f-85

Thanks for the info. Im gonna put something better in this winter. And thats gonna give me more options. I need to set up my rear better anyway. Was thinking of boxing my control arms, and adding a rear sway bar.