[70temp455]

Broke my P 8.2 and got a Cutlass 8.5 10 bold from the local Classic Car parts yard. The guy said it would bold right in. It did, the drive shaft didn't !
I'm having it shortened 1-1/2 " and ahving new U-joints installed.
In preparing the rear-end for insertion I drained and the gear lube and relaced the gasket and cover with a Summit Chrome cover and POR-15 the rear drum to drum.
41/16 = 2.56
Anyone know what other gears will fit this carrier ?
Thanks in advance !
Andy

[marxjunk]

2.41 to 2.76...with out any mods............

[GStage1]

GM used that center section up to 1987....so you can use any set-up you want...best bet is the full size 80-87 wagons...many have 3.08-3.23 gears and some have posi units. After 1987 GM went to 30 spline axles so those carriers won't work.

[marxjunk]

Anyone know what other gears will fit this carrier ?

2.41 to 2.76

[b-man]

The 8.5 10-bolt corporate rears used only two differentials or carriers.

One for 2.41 & 2.56, the other for 2.73 and higher numerically.

That's it.

[70temp455]

So I'm screwed as far as far as making any worthwhile change to the rear end and carrier I have now.
Olds site saide a 70-81 camaro carrier and gears would work but do I need the JUST the carrier and gears or would I need to swap the entire housing ? I'd assume a camaro rear would be a bit narrower and would not fit a LeMans, so just the carrier and gears then ?
Thanks Guys !
Andy

[b-man]

Just the differential needs to be changed, not the entire axle housing.

Forget about using any Camaro/Firebird housing, you can't swap a leaf spring housing into a car that needs a four-link housing.

Just use the carrier and gears.

[67drake]

I was in the same boat. I picked up a 71-72' Buick/Olds 8.5,but it had a 2.56 posi in it. I set it up with 3.42 gears and a ring gear spacer behind the ring gear,so that I could use the 2 series posi carrier with the 3.42 gears.
That rear has been sitting in my garage for 2 years now because I decided NOT to take the chance of using the spacer behind the ring gear. Too risky with the way I drive my GTO. I picked up a 3 series Eaton posi just yesterday,so I'll be redoing it all in the next couple weeks.
Those 8.5 rears are supposed to be stronger units then the 8.2's that came in our cars originally,so you will have a strong set up when your done (If you DON'T use a spacer!). I've heard if you put in a 30 spline carrier and axles,as opposed to the 28 spline that came in them stock,they are as strong as a 12 bolt rear.
As B-man said,the 8.5 carrier and gears from a Firebird will swap over,just not the housing. Also the carriers/gears out of many GM 8.5 rears from later years will fit in the early 70's housings. I forget the cut off,but somewhere in the late 80's as I remember.

[70temp455]

Don't know where, but I'll be lookin fur One.
Any Ideas ?
Thanks again Guys,
Andy

[GStage1]

Andy,

You should recheck your measurement for the driveshaft.....I have done many changes from 8.2 to 8.5 and always need to shorten the d-shaft 7/8-1......your 1 1/2 is a little too much to take off...you can look up the driveshaft measurement in the assembly manual.....I think it is 56 3/8 from center to center of u-joints.

[GStage1]

You can get posi units from many GM cars.....8.5" rear was the standard rear for many cars........except 78-87 G-body (Monte Carlo, Cutlass, Grand Prix, Malibu, Regal)

1988 is the cut-off year for 30 spline axles...so stick with pre-88 rear and you will be set.

[70temp455]

I set it down and measured like the Drive shaft guy said to do. It came out to 1-1/2 needed to come off. Now that it is shortened and sitting down, the shaft is about 3/8 further out of the trans than it had been(which was about 1" out).
Do you think the extra 3/8 will be an issue ?
Thanks,
Andy

[GStage1]

3/8" should not be an issue.

[b-man]

If you're changing the carrier or diff to get into the lower gears you might consider a new Eaton posi. They come in both 28 and 30-spline versions, the one pictured is a 30-spline with 3.42 Yukon gears teamed up with Moser alloy axles so it can take a beating:

[70temp455]

So, when carriers advertise "splines" they are refering to the splines on the axles ?
And, How many splines on my stock Lemans axles ? 28 ? 30 ?
Ahh, so much to learn !
Thanks,
Andy

[b-man]

The spline count refers to the number of splines on the axles, these engage into the splines in the side gears on the differential. The greater the number of splines, the stronger the axles will be.

The Cutlass 8.5 rear end you picked up has 28 spline axles. They are true heavy-duty axles already and can take some abuse, but of course for some extra cash you can get aftermarket axles that are even stronger if you plan on having high-horsepower or like to beat on your car a lot.

I had the 8.5 rear end pictured above built for a car that will have around 480 horsepower. I decided to put some heavy-duty parts in the rear end for added insurance against breakage.

[russosborne]

Ok, I am feeling really stupid right now, but I am not quite sure what you guys mean by changing the differential. Might be my old Ford history again, but when I think of differential I think of the fords where you remove the entire "pumpkin", and I know on the BOP you can't do that.

Is "rear end gears" = "differential" what you guys mean, or am I still cornfused?

This is what got me
"The 8.5 10-bolt corporate rears used only two differentials or carriers.

One for 2.41 & 2.56, the other for 2.73 and higher numerically.

That's it."

Sorry, my brain hurts, it's been a long week here.


Thanks,
Russ

[67drake]

Differential= http://www.drivetrainspecialists.com...duct-1986.html

I can understand your confusion. I see people interchanging the terms alot. Differential is usually the ring gear carrier,and the parts of it-spider gears,posi clutches,ect. But I do see people use the term differential when they are referring to the entire rear end housing.

[b-man]

On the GM rear ends being discussed here the differential contains the spider gears and side gears (and sometimes posi clutches too), the ring gear bolts to the differential. The differential unit installs from the back with the pinion gear already in place in the housing. This type of rear end where the differential loads from the back is known as a Salisbury design.

Same differential definition applies to the Ford 8" & 9" rear ends except the design of that rear allows you to remove the differential/ring gear assembly along with the pinion gear from the front as one unit making for easier gear changes. The Ford rear ends like this are a Hotchkiss design.

The '55 -'64 big Pontiac 9.3 rear ends as well as the '55 -'64 8.2 Chevy rears were all Hotchkis. The later Ford 8.8 rears are Salisbury.

-----------------------------------------------

In order to accomodate different gear ratios the differential unit needs to be able to accomodate the different gear ratios. Sometimes a new differential unit with an offset flange to mount the ring gear is needed to do this, hence the 2 different differentials for the GM 8.5 and 3 different ones for the GM 8.2.

A 2.56 gear has a very large diameter pinion gear compared to the pinion on a 4.10 gear. The ring gear will be offset further to the side on a 2.56 rear than on the 4.10 to accomodate the larger pinion gear diameter. In the case of the GM 8.5 the 2.41 & 2.56 will work on one design, the 2.73 and higher gears numerically will work on the other one.

[russosborne]

Ok, I think I got it.
So from reading here if I were to buy an 8.5 from an Olds or Buick 71-72 A body I either need to make sure the differential it comes with will work with whatever gear ratio I plan on using, or plan on buying another differential as well?
The external housing of the rear end is the same, it is the internals that determine what range of gear ratio's you can use?
Sometimes I think I really am stupid. Other times I am sure. :-)
Thanks,
Russ