Vistabrat72

Good evening to all. We have our 1966 Ninety-Eight LS, it has the Pontiac style rear axle assembly as identified by Joe P. a few years ago. I have obtained a 1967 Type-O Anti-Spin rear axle from a 1967 Oldsmobile Ninety-Eight. My main question is, mainly, will the driveshaft presently on the 1966 be a direct fit to the 1967 axle once the axle is put on the car? I guess the answer would come from a parts number manual. If anybody could chime in (Jim from JD Race - Monzaz?!) who has a lot of experience with differentials, it would be much appreciated. Thanking all in advance for any help provided. Best regards, Howie.

monzaz

Yes, If everything is already fitting correct and you go with a 67 rear it will all be the same rear .65 66 are the same big spring pocket.... 67 ?? I am unsure about the spring raised pocket size..I think they shank it down....then 68 -70 has small spring perch pockets.
So You might have to switch to 1967 68 springs to used that complete rear. IF all your putting in is the POSI which is does not sound like in the posi... guts are all interchangeable from 66-67 .

joe_padavano

The question isn't the spring pocket, the question is: do the 8.875" Pontiac axles have the same axle-to-pinion flange dimension as the 9.3" Type O axles. The OP is asking about any changes to driveshaft length.The parts book is not clear on this, as the 67-up driveshaft for the C-body cars has a different part number than the 65-66 driveshaft. Unfortunately that doesn't say anything about length.

Vistabrat72

To quote Joe P. (thanks Joe) yes, this was the basis of the question, but what Jim also said helps! Because the parts book is not clear on length, I will have to carefully rig some sort of device to get axle C/L to pinion flange lengths between the two axles. Reason for the (possible) project is for us to make it up a fairly steep and winding road up to a cottage in summer. The car does it now, but often one wheel will let loose and scramble for traction. Our 72 Vista with Anti-Spin makes the trip with never any wheel spin. Drive shafts can be fabricated indeed, U - joints can be found, springs can be changed to if need be, just want to go into the project well armed! Thanks to both of you Joe and Jim.

monzaz

Yep, Wow must have been tired...lol. I skipped right over the ANTI SPIN hint...lol. But yes whole rear to whole rear will be the same driveshaft length. BUT AGAIN you will still have to deal with the spring perch issue. The difference in the books driveshaft part number MIGHT BE because the car chassis has different mounting point of the engine in the bay from 65 66 chassis to 67 and up or maybe it is just a design change in tubing ??? BUT if your car is together and running and all your doing is swapping the 8.875 rear for the 9.3 rear you should not have to do a driveshaft swap or modify the driveshaft. U-joint is the same 1 1/8" the pinion offset from a 9.3 to a 8.875 is the same center of housing to saddle of the yoke. I just do not know about the spring perch deal from year to year ... I use to have tons of the full size car rear end laying around... ALL GONE now...like my old brain.... lol. even if you did the math .425 is the difference in ring gear diameter the most is could move the pinion forward is 1/2 that .2125 which is not even a 1/4" difference.
GUTS WILL NOT INTERCHANGE.... from 8.875 Pontiac to a 9.3 Anti spin. oops...VERY sorry.
Jim
JD Race

Vistabrat72

Thank you so much Jim! We all have days like this. My long work hours have the same effect too at times! This is truly the site to get all the correct answers with no sugar coating. Your help (and Joe's) have been immense, I do feel confidant with the expert answers, I will be examining the spring perches very carefully, I can with the Type-O, it is in the garage, and then look at the axle in the car. When I do this (hopefully) later in the summer I can follow-up with pictures etc! Best regards, Howie.