This is a topic that I have been very interested in myself. My suggestion would be to go to the cadillaclasalleclub.org forum and ask the guys there. I have heard there is like one or two people that is even capable of working on these particular rear-ends mainly because the ring gear is riveted onto the carrier, making it almost impossible to service/rebuild.

Your real concern should be to go and find a posi carrier that will fit in the housing... after-market preferably (one that will be serviceable in the future) However if you really desire to do so, you can hit up the junkyards and look for the little posi tag that goes around the fill hole on the pumpkin!

 

Your best bet would be one of the disc rear ends out of a 94-96 Impala SS or Caprice 9C1 (police package). There is a SLIGHT difference in width. To get this under your car may require cutting off the mounts and redoing them to work with your trailing arms. Measure the width of your rear, then get over to the impalassforum.com to see if it is close to yours. Note that if you want to get one with factory posi, look for option G80. It was standard in the SS, optional in the 9C1. Even if you get a core, gearsets and posis are readily available and affordable.

 

That rearend is a childs toy compared to the stock Cadillac one. The stock rear-end is suitable for a dumptruck, the stout third-member design... thick axle shafts and actual press-on bearings... yeah press on bearings, not the cheap roller type. Also remember the stock Cadillac rear-end has an offset pinion shaft to proper line up with the tranny tailshaft.

 

Thanks for the responses. I'll do some measuring and see what I come up with. It's not a priority on my project list yet, but I'll be sure to come back and report what I find out as I work on it. I've had such a hard time finding info, I'd like to save someone else the trouble.
You rock.

If anyone else has info, please share.
R

 

I just remembered: check with Powertrax to see if they have an application that will work! You would get to keep your stock rear, your non-posi housing, and you wouldn't have to rebuild/reshim anything. If they have something, this would be by far the easiest option.

I have no doubt that the Cad housing is stouter than the 8.5 "corporate" rear in the B/D bodies. That 8.5 is plenty strong, however, and has no problem standing up to hp/torque numbers over 400 at the wheels in a 4500-5000lb car. You've got a 93 - when is the last time you heard of someone grenading the 8.5?

 

I have no doubt that the Cad housing is stouter than the 8.5 "corporate" rear in the B/D bodies. That 8.5 is plenty strong, however, and has no problem standing up to hp/torque numbers over 400 at the wheels in a 4500-5000lb car. You've got a 93 - when is the last time you heard of someone grenading the 8.5?

I have had my 8.5" apart several times and used to have the 3.42 posi setup. Just comparing apples to apples here... that Cadillac rear-end is a brick shithouse compared to my 8.5" And again you have an issue with a straight drive-line.

My question is... will the 12 bolt Pontiac rear-ends that are found in Caddies a couple years after '68... will those swap into a '68? I personally don't see why they wouldn't, and I am pretty sure those rear-ends are quite serviceable??? Problem there is... after 69' they stopped using these high quality rear-ends and went to the non-thirdmember style housing with the roller bearing setup with the axle shaft as the inner race .

 

I'm wondering what happened here... I'm measuring my 68 rear in the morning and gonna hit my local salvage yards for a posi unit..

 

I never pursued the idea any further than the info in this thread, honestly. We had a kid, car project slowed down and I've since sold the car and moved. I miss that '68.

Even though I'm not involved with this forum much anymore, I'd encourage this thread to continue with your posts to see if there is a solution. Best of luck!
ryan

 

There was a guy on ebay last year selling ring and pinions and posi units for just about any GM vehicle. He even had a posi for those 8.75 rear axles.

 

im kinda of an cadillac newby but are the 1977 deville come stock with an posi rear end

 

You could get a 77 with a posi but it was optional.

Axle for a 68 would be the 3.15:1 posi found up to 1976. Post 76 things got a whole lot smaller. IO've only seen one 3.15 posi in the flesh. Unfortunately for me it belonged to the guy in the next lane at Raceway Park in Englishtown.

 

wow so my caddy is a rear because it has the posi rear end on it

 

Not really. Just the option is hard to find.

 

what is the benefits of positraction rear end

 

Other are 3 basic diff types. Open has zero resistance and allows all power to go to one wheel if it's spinning.
Limited slip has friction packs that attempt to equalize power between both wheels. It works good but under hjigh load/stress only one wheel will spin. Posi traction sends equal power to both wheel pretty much all the time regardless. It still allows a slight diff in wheel speed so you can corner.
For most cars unless in the snow belt an open diff is fine. If you get stuck it sucks because only one wheel will ever spin. In the snow belt, limited slip will suffice most of the time. Posi traction is the gold crown diff option.

 

Little off topic and much later but does anyone think a 68 Cadillac Deville could tow a 14' Box trailer?

I rebuilt my 472 to 8.5/1 compression and a RV Cam, Fuel injection etc. It also has a new 400TT with cooler and Front 13" Willwood brakes and 12" rear. Also Accuair air ride.

I believe the car is probably stronger than most trucks. I was concerned about the rear end though. I understand it is pretty stout but, what does anyone think about towing with the standard gear?

I am am relocating to FL from San Diego which I did with a Ram 1500 to San Diego. I'd rather not have the Caddy shipped again when it is more than capable of doing a trucks job. Unfortunately the truck was too much here so I sold it and I only have SRT8 as another car.

I'm sure I would need a tow commander and it has load leveling.

Anyone?
Thanks

 

I think it could do it with proper equipment if the trailer is under about 4700 lbs.

 

I got a 1965-79 Hollander Interchange in front of me and the Cadillac rear has no interchange except for another Cadi of similar vintage. 68-70.

Fyi - Posi-traction is a Chevrolet brand name for its limited slip differential. Cadillac called it by another name, Controlled Differential.

 

depending on the weight of the trailer I'd say you'd be fine. those engines are real stump pullers.

 

I agree the engine had ridiculous torque. Though with my new mods it is meant for gas mileage. It probably has around 400's in Tq now.
I am worried about the rear though. 17' trailer and the WT of the car is 9700lbs if it is in fact 4700lbs restricted like someone else stated.

I had a problem with a new Dodge Ram 1500 trans overheating going up the mountains east of San Diego. I had to turn around and sleep in Imperial Ca till it was cool enough 0430 in the morning. That thing is meant to pull too.

 

There is an option found in some mid 90's hearses and limos. That is the 14 bolt truck rear you mentioned. I have one in my Federal hearse. The mounts will be different I am sure. But the width should be close. It is a drum brake rear but the drums are huge. Not sure if they come in posi from the factory but you can get posi's for them. Mine has 4.10 gears and a tru trac diff.

 

Man I'd love a 4.10 posi in my car for about 2 tanks of gas.

 

:yeah: That'd be a fun 26 minutes.