I am planning on installing a "corporate" 10 bolt rear end in my 1966 442. The only issue I see is the axle spring perch. The 66 is flat with a clamp plate and the "corporate" has a round raised circular flange. I have new 66 springs which I would like to retain. Is this possible and what do I need to do to make the axle swap work? If I cannot use the stock springs, what should I use instead?
Thank you in advance for your help. Larry

 

You need to use the springs for a 67 with the Type O axle, which used the later style perches. The only way to retain your current springs is to weld on the perches from the old axle.

 

I'm looking to do the same thing. I was told that the mounting ears for the upper control arms are at slightly different angle in the horizontal plane...something like 43 degrees on the 68-72 and 37 degrees for the 64-67 or maybe I have that backwards ???

 

The angle can't be different, as the 1967 cars used the exact same Type O housing (by part number) as the 1968 cars.

 

You can use your 66 springs with the cup type retainer on the housing. Also, you cannot use 1967 rear springs on a 66 because the 66 springs have tangential tops and pigtail bottoms while 67-72 have pigtails on both ends.

 

If you are installing a 1967-up rear end in a 66 (which was the OP's question), you can and should use the 67-up springs.

 

OK, I did not know that, so that make my angle belief pretty unlikley
So the arms would be different because of chassis mount locations and what about this:
Mike at Quick Performance says that he uses three different Jigs for the GM rears. One for 64-7 , one for 68-72 and one for 73-up.
...The 67 Oldsmobilty site http://www.oldsmobility.com/old/10bolt-tech.htm also mentions ear locations on the sixth bullet in the notes section...

BTW Mike did not mention anything about angles and neither did the Oldsmobility site, so I am still confused about Mikes need for three jigs if the olds rear like Joe mentioned is the same p/n for 67 and 68, and Oldsmobility making mention about ear location. Somethings not adding up...unless this is a Chevy only situation?

 

ALL 64-72 rear can be interchanged in all A-body chassis in this era...PERIOD


You will have slight differences in spring perch mounts and drive shaft length and u-joint sizes. BUT all are fairly easy to over come with a small amount of brainstorming...

AS stated already but pulling it all together-

1964-1966 will usually have the flat spring perch and cup and bolt install and the tight pig tail on the rear end perch mount surface and a larger 6- 8' open top pocket in the frame area.
The 1967 rears are unique one year deal where they still use the big upper spring pocket but use a slightly smaller lower diameter pig tail to fit the NEW raise cup perch on the rears normally found on all 67-72 rears. In this year the BOP rears were wider by a 1/2" on each side.
1964-1967 also had a LONGER upper control arm and this is why people say the early rears will not fit etc. The chassis rear cross member is further forward to the front of the car where the upper control arms mount to the frame - So as long as you use the control arms that belong to that chassis you will be good. with any rear.
68-72 all are the same and generally the only difference will be with the u-joint from Chevy to B O P swap rears and the 1971 1972 8.5 swap into any other 64-72 will need the drive shaft shortened. WHICH should always be measured after you get the rear in the car and the suspension loaded.

Hope this helps clear it all up.

Jim
J D

 

The big issue is not the perches on the differential. Either the plate and cap or the cup style perch can work with a pigtail end spring. The issue of concern is the car's frame. 64-66 frames have formed cups for tangential ended springs, while 67 and later frames have formed cups for pigtail ends. Thus, 64-66 rear springs will have one pigtail end and one tangential end. 67-up rear springs will have two pigtail ends.

 

Joe,

You are correct. Sorry for the mis-information. I had it in my head that the full coil on the early springs went down, but it goes up, as you correctly point out. I guess it's been too long since I did the rear suspension on an early car.