I have an anti-spin type O rear (1967 Delmont 88, 9.375") that is a 2.73 or 2.78 (whatever stock ratio was available near 2.75). What ring and pinions will fit in that differential?


The car was recently converted to a 4 speed and even with a 3.11:1 first gear it is way too high. I also have 235/80-15 tires which aggravates the issue.


Ideally I would like to go with something around 3.50:1 but am not sure what the lowest gear that will work is.


Next... is anybody making gears for these yet?


Thanks,
Chris

 

when i had my 68 i was looking for gears and monzaz said he had a set of 3.23 gears as well as mentioning they were the lowest gears available. i sold mine about 3 years ago so idk if he'd still have them

 

i would consider swapping in an 8.5 rear end out of a an early 90's caprice, looks to be about the right width and will be plenty strong with aftermarket gears and posi.

 

Thanks! Knowing that 3.23's are the lowest that will fit is a big help.

 

Have you spoke to Brad @ Fabcraft ? He is in N TX and is the go to guy for the 57-64 Olds Pont 9.3 rears. He may be able to help. He offers new and used parts and can machine stuff to work as well. May be some interchange possibly.

 

67 is totally different than the Gasser 9.3
65-70 are intergral housing non third member hog head drop out.

We have been trying for years and there is nothing to retro fit. We are just going to make a 14 botl 9.5 complete GM rear to replace the old 65-76 FULL SIZE cars. Just been so busy with regular rear builds. Jim

J D Race

 

I know it's totally different drop out style , I have built them and bought sold several. Merely stating he could still call Brad he may have some of these odder different later ones. There is some random interchange on GM stuff sometimes. Like the 67-70 type o 12 bolt 8.5 10 bolt uses same carrier bearings as 71 up Corp 8.5 10 bolt. Or like retro fitting 8.5 posi to a 8.2 BOP rear end. It's been done. This particular case may be the most oddball difficult case with no options . Just saying the gear dimensions themselves I was curious about on this later type . Like the Pont olds B body 8.875 12 bolt with 10 bolt cover 31 spline. It's 65-70 but then the second version was 71-76 similar but different . Pinion spline and pinion diameter ? The 9.5 14 bolt project is interesting .

 

Wouldn't it be an easier, possibly better, idea to do 8.5 rear swaps. Easy to get parts plenty strong? I know I wouldn't want a massive hulk of a 14 bolt under my car, just sounds wrong to have a 1 ton truck rear end in a car

 

Hello everyone I have for sale a 72-73 posi 12 bolt Riviera GS Stage 1 c/w 3.23 gears 9.375 ring gear, 11"drums complete. even E brake cables

 

9.3 " full size car rear is actually Heavier than the 9.5 14 bolt rear we use.... I do not think you under stand how big your 9.3 Olds rears are...


14 bolt 1 ton rear is a 10.5 (TRUCK ONLY) the 3/4 ton is the 14 bolt 9.5
14 bolt rear was used under the SS trailblazers which is not that big and heavy of a vehicle. They also used the corp 14 bolt 9.5 under the 90 -96 limos ...IF you can find one of those rears...Holy grail in my book you can retro fit that into any 4 link A-body to Full size car... It will haver the upper cast in control arm bushing in the center. Everything else i can narrow and change the brackets from another rear to make it fit.

WHERE DO LIMOS GO TO DIE ANYWAY!!!!!!

14 BOLT 9.5 is the same size pinion shaft (1.875) as the olds and Pontiac 9.3 and 8.875 (12 BOLT 10 BOLT COVER FULL SIZE REAR) etc.

I have been making 9.5 rear for aLL GM leaf spring BIG BLOCK and twin turbo (CAMARO NOVA CHEVY II) cars for years... narrowing, changing the ends and using 33 spline custom Moser axles that are BOLT in and use the ford large bearings with GM car ends. (7900 moser Billet ends.) - 9.5 GM 14 bolt rears are great as they have a good selection of popular ture trac, eaton, auburn, power trax... posi units to use like cars.
10.5 full floater 1 ton rear is a MASSIVE GM rear and is VERY popular with the off roaders and pullers and are expensive...NO ONE wants the 9.5 in the 4x4 world because it is a semi floater rear (c-clip rear) .

This is not something I have been doing for a hobby or for FUN for 30 years... THIS is my JOB... I came out with my 9.3 OLDS Pontiac posi before anyone else in the business... Fabcraft went with Auburn to get his limited slip done...after I had mINE OUT AND WAS MAKING MONEY WITH IT. I could not wait for the unit to be built, it was suppose to be a POWER lock which is what we were all WAITING for from them...JUST never happened so I did my own before the gasser craze ended.
I Also acquired all the 8.2 68-70 Buick parts to get that project started and convinced the V8 Buick guys to use Brad at Fabcraft for this project as i knoew he would put the care and detail into making the gears correctly. I was doing all this Posi conversion with Stock GM gears stuff before it was even popular... 8.5 units into 8.2 housings etc. A lot was learning from stuff that did not work either... Sometimes learning is expensive and time consuming.
I am always looking at NEW differentials that come out to see if ever anything can be converted to use on the old vehicles... just slip pickens when no one makes rear wheel drive cars and now even talk of getting rid of CARS all together on some manufactures...

1971-1976 8.875 did not change its pinion spline it is still 1.875. Both the 8.875 and the 9.3. The pinion spline did change to 30 it was the axle spline going to 45 degree 31 spline and the axle bearing system all used the same a10 / set10 oiled bearing system. Also the axle tube end flange pattern changed and has NO support for any aftermarket disc brakes either...

Correction on Gearman69 post - Your referencing the A body 8.75 rear HAS the 10 bolt cover and 12 bolt ring (optional in the cutlass and el camino HD applications ) which uses a 1.625 pinion / 30 spline pinion and was later the heavy duty rear for the B-body cars / wagons.


MACHINING PARTS-
The reason some stuff can not be done is merely MONEY... anything can be made with all the CNC machines etc. BUT if you can not do it for a reasonable amount of money then it is a MOOT point. Guys like us have to stay in business... can not make bad investments that do not pan out or we go under.

All the gears Brad makes take MORE money to create in small quantities...If he could run more it would be cheaper BUT you still have to RUN BIG equity to get the price breaK...... they get you coming and going on that deal.

I make Monza rears too, not many because those guys do not spend the money on the rears...The car cost less than the rear to make... I have 2 Monzas ...I like them too. custom rears are costly no matter the size it is generally always going to be be the same expense.... Custom is Custom... they Rare EXPENSIVE.

pictured are custom rears Dana 60 1968 riviera rear which still uses the stock 12 inch drum brakes... WHY... cause the customer wanted it that way...
14 bolt Camaro and 55-57 Chevy rear and finally the one 12 bolt Chevy MONZA rear with Wilwood brakes... 3750.00 rear for a MONZA???

ANYTHING CAN BE DONE....HOW MUCH DO YOU WANT TO PAY?

Jim
J D

 

3.42 is the steepest for the OLDS 12 bolt in the FULL SIZE CAR. pRETTY SURE THE 3.23 IS THE FINAL ratio on the mid series carrier ...then 3.42 fit a next carrier up . I think it has 3 series 2.41 2.56 ratio then 2.73, 2.93, 3.08, 3.23 then 3.42 or 3.23 and 3.42 might be on the same carrier...Anyone have a manual that says any of this... ??/
1965-1970 9.3 Oldsmobile full size cars and 1971-1976 Any car full size with a 455 and usually wagons
Jim
M
J D Race

 

The 1972 printing of the Olds Parts Book shows only one P/N carrier housing (well one open, one anti-spin) that accepts all available ratios (2.73, 3.08, 3.23. and 3.42) for the 9.3" Type O.

 

What happened to 2.41 and 2.56 ratios?

 

 

Humm. So your saying there is only one carrier? 2.73 - 3.42
I do n=know there are at least 2 series carrier high and low because i have them on the shelf.
2.56 is on a different carrier .

 

where are you and how much?

 

Jim, this resurrected thread is from 2015.

 

oops...lol.