midnightleadfoot

Hello.
What rear axle would be under a 1975 olds cutlass salon?


I'm guessing a 10 bolt, but back then was it the "corporate " 10 bolt, or?


Driving it home today it was raining and even light gas and I mean just off idle, the pass side tire would slip/spin..And this is an as stock as a mid 70's smog 350 gets so it's not a powerhouse. I'm sure the old tires are hard as rocks, but I may want to add limited slip..


Thanks in advance for any insight on this..

Inline

Someone who knows all the quirks can confirm, but pretty sure its 8.5 with bolt-in axles.
Atleast on 76' it is.

Theres some highly suggested guys doing rears and selling correct parts on this forum, but from my personal experience i can recommend Monzaz for all your needs on rear.

66-3X2 442

I have a limited slip rear axle out of a 75 Hurst Olds that's in great condition for sale. Contact me @ pchopesq@aol.com

Thanks

Mike

oldsmobiledave

The diff is an 8.5" 10 bolt with bolt in axles.

Change your tires ASAP. Why are you driving on old hard tires?

midnightleadfoot

Do you bring a new set when you buy a car, or drive it home on the tires on it?

oldsmobiledave

I load the car in my trailer or I swap the wheels on the car out for wheels with safe tires on them. Too many bad things can go wrong driving on old tires.

midnightleadfoot

Wives tales..
Tires that are without dry rot cracks, and in good shape are just fine.
The tread rubber gets harder from age from the loss of oils..
Like anything.. you have to look things over..
The tires are 7-9 years old per the dot stamp..
and car was garaged.. Now if they had cracks all over.. Ya..
They will be pulled looked over again.. and replaced as needed..
They were more than fine for the trip home on 45-50mph roads..


I don't have a trailer.. and if it was on dry rotted tires. it would've either been towed or driven to a local tire shop..


You can't go by age alone..

oldsmobiledave

You are mistaken. There is a date code on tires for a reason. You can't tell when a tire will come apart just by looking at it. The absence of visible dry rot on the tire exterior is not the final say on tire safety. Too many horror stories out there from guys who had your perspective but learned the hard way.

Google the issue then read and learn. Glad you made it home safely. Ultimately it is your car and your decision. Good luck with what ever you decide.

Enjoy your new car.

svnt442

You also can't just assume that old tires are bad.
I once took tires off of a Corvette that came in for new tires because they were old and the car had been sitting in a garage for 20 years. They had good tread on them so I put them on my 1970 Cutlass and proceeded to beat the crap out of them for a couple years with zero issues. This included runs over 100 mph, days at the drag strip, and 600' long burnouts mixed in with daily driving.
If his tires didn't come apart on him...GREAT! It was his judgement used to determine if he felt safe driving on those tires for what he needed to do. Don't shoot the guy because you might have done something differently because every situation is different.

midnightleadfoot

I deal with good-year engineers weekly..
I think I can judge a tire better than most, but thanks for your input..

midnightleadfoot

Back to the rear end question. is the diff in these with the bolt in axles the same as the chevy 8.5/8.6 ?
it seems that vendors list 2 one for 28 spline axles(chevy trucks) and 30 spline that is listed only for chevy vehicles..


I know from having chevies they are c clip .. so are the guts of the olds rear in 75 the same as the chevy i.e. the diff and bearings/gears?


I know vendors are known for screwing up the listings the part fits.. but I'd thing if it fit more than just chevy's it not miss all of the other makes under the g.m. banner..

svnt442

I'm pretty certain that the guts are the same, but the axles are different.
MONZA!!!!!!!! (that's a call for clarification from a guru....lol)

oldsmobiledave

I once bought a wrecked 1972 Cutlass. I tried to buy the car for several years but the seller would not sell. I got it cheap after it wrecked due to a tire blow out. The tires looked great.... right up to the moment of the blow out.

Are you really bragging about running 20 year old tires? Really? I respect your right to live in denial. Carry on.

svnt442

You're missing my point...

I get that old tires CAN be dangerous to drive on, and more times than not that is the case, but not always. I am not in denial in any way, but just trying to make a point. Don't berate the guy (or me for that matter) for making a choice. I ran those tires in all seasons for a couple of years with zero issues. Would I recommend that someone else take that chance? Not really, but I did and that was my decision to make.
On another note I bought some used tires that were about two years old and drove on them for maybe three years before I had to replace them due to MAJOR cracking and a bubble in one of them.
Date codes are not the end all-be all of deciding if you can use a tire or not.

midnightleadfoot

Clearly They didn't look great.. or it not let go.. A tire shop would've seen and found the bad in those "looked good" ties. on that 72


It either was dry rotted, or had brake fluid leak and drip down the inner sidewall.. rear sal leak will also put a weak spot in a tire..
This is easy to spot as both leave a stain..
The other failure would be from the layers separating .. this is also easy to spot side wall will have a bump from the tread to bead.. or the tread will squirm..
Most times a tire that "looks good, but fails was run/driven on with almost no air in it.. This can sometimes be hard to tell, but most times the owner knows it happened.. so no surprise there..


Fun FACT a new.. made 4 months ago.. just bought and installed tire can also fail... some fail before you get the tire on the car..
I've had a few blow on the balancer..


I get the comments,, and all but before the 2000's they didn't date tires and you had millions of cars on the road with just bought new tires that sat on a rack for 10 years..


Why do you think they now have the buy 3 get one free.. or buy 2 get 2?
it's because the date on the tires are getting old..


As for my drive home on back roads mostly.. even if one let go at 35mph.. it isn't going to do anything.. other than go flat..


As soon as the new wheels get here ,it 'll get new shoes..


But most that are up in arms over the tires will not think twice about putting the spare on without question..
Or ride on that donut for days.. lol
Stay safe

Fun71

Basically the same other than the c-clip / bolt in axle difference. The side gears will be different for c-clip/no c-clip.

midnightleadfoot

Thank you..