81 M body 8 1/4 cop rear end with sure grip

Remow2112

Well-Known Member
Joined
Mar 10, 2011
Messages
154
Reaction score
37
Hi all,

Who has the specs for what weight axle lube and does the cone type Sure grip require limited slip additive?

Thanks!
 

BudW

Moderator
Staff member
Joined
Mar 4, 2012
Messages
5,121
Reaction score
1,485
Location
Oklahoma City
This is from my '80 Factory Service Manual (for 8-1/4" differential only):
Screenshot 2022-01-17 184208.png


4.4 pints - which is 2.2 quarts (or 0.55 gallon).

Limited-slip differentials that use clutch disks require additive. The cone type carriers do not use clutch disks and therefore no additive is needed.

The above doesn't mention the weight of oil, so I found this, from the same service manual:
Screenshot 2022-01-17 185304.png


Hopefully this helps.
BudW
 

Remow2112

Well-Known Member
Joined
Mar 10, 2011
Messages
154
Reaction score
37
Check dippy.org. I see them in the adds there from time to time. Every M body sold to law enforcement got an 81/4 and suregrip. rear sway bar too.
 

BudW

Moderator
Staff member
Joined
Mar 4, 2012
Messages
5,121
Reaction score
1,485
Location
Oklahoma City
Every M body sold to law enforcement got an 81/4 and suregrip. rear sway bar too.
That is not an 100% accurate statement. I would say "most law enforcement" got the 8-1/4" differential and rear sway bar/larger front sway bar setup - but not all.
I would also say very few police cars came with limited slip. Police cars (for the most part) are bid upon from the big three (back then). The police dept would give a "min specification" and sometimes a "would also be nice specification" for cars to be bid upon. If limited slip wasn't mentioned in the "min specification" sheet, then it didn't get added - and it was rarely mentioned.
I know for a fact that police cars - that maybe 5% came with limited slip - and maybe fewer than that.

I have even seen some F/M-body police cars (for Tulsa (OK) Police Dept) that came with 7-1/4" differentials and no rear sway bar. They did come with the modified door strikers and other body "police" changes - but otherwise was a plain Jane, F (or M-body). Most police departments were on a tight budget.
HeHe, I even remember being chased by the Tulsa Police, and it took him two plus miles to catch me, in his Ford Fairmont I6 car - and I wasn't even trying to run from him. I had a rolling stop and thought no one was watching. I pulled over thinking police - flashing lights, you gotta pull over to allow them to pass (two lane road) and he got behind me. I wasn't even speeding the entire time.

Most Highway Patrols and (US) Federal law cars came with all of the goodies.
BudW
 

Remow2112

Well-Known Member
Joined
Mar 10, 2011
Messages
154
Reaction score
37
Good info Bud, I have always been in AZ and I can't tell you how many cop cars I pulled apart. But everyone of them had an 8 1/4 sure grip and a sway bar. Maybe AZ was big on those bid options. The axle I am using right now came out of a detectives car. In retrospect I should have bought the whole thing. The engine threw a rod at 96K. Rest was in great shape.
 

Loy

Member
Joined
Dec 1, 2021
Messages
8
Reaction score
1
Location
Franklin TN
I need one of those rear end assemblies with either 2.94 or 3.21....complete so I can just swap. I have a 7.25/2.71 in a 5th Ave but I need a different ratio. Any thoughts where I can find one?
 

Mikes5thAve

Well-Known Member
Joined
Mar 3, 2020
Messages
1,375
Reaction score
538
Location
Canada
8 1/4 and sway bar was stock on them, sure grip wasn't. It seem to be a good mix of ones I used to see with it vs without.
 

Loy

Member
Joined
Dec 1, 2021
Messages
8
Reaction score
1
Location
Franklin TN
I have a 1989 5th Ave with all standard 318. I don't want to modify the engine (car only has 51,000 miles). I just want more pulling power and overall performance will be greatly improved with the ratio change. Thanks.
 

Remow2112

Well-Known Member
Joined
Mar 10, 2011
Messages
154
Reaction score
37
The 8 1/4 was used in a lot of stuff. Here is the best list I could find. The truck and jeeps are a good place to look for gears and a sure grip. If all else fails you grab the whole rear axle and have new pads welded on and shortened.

I know a lot of A-body guys like to get 8.8 out of ford Explorers. The tended to have good gears and a "Trac loc." They are offset but what they do is go and buy the shorter axle shaft out of another one then shorten the long side.


Dodge Charger 1968 - 1975 Rear
Dodge Dakota 1987 - 2004 Rear
Dodge Durango 1998 - 2004 Rear
Dodge Ram 1500 1994 - 2004 Rear
Dodge Ram 2500 1997 - 2001 Rear
Jeep Grand Cherokee 2005 - 2010 Rear
Jeep XJ Cherokee 1991 - 2001 Rear
 

LSM360

Well-Known Member
Joined
Nov 28, 2011
Messages
812
Reaction score
314
Location
Melbourne, Florida
I need one of those rear end assemblies with either 2.94 or 3.21....complete so I can just swap. I have a 7.25/2.71 in a 5th Ave but I need a different ratio. Any thoughts where I can find one?
I'd try nationwide craigslist search. www.searchtempest.com Once in awhile I see one there but not so much anymore on dippy.org but worth trying! The nice thing about the Police one is it will definitely have the bigger brakes too and probably rear anti sway bar and brackets so I'd try and get it all. Chances of finding one close to you are slim so shipping will be steep if you even find someone willing, but you never know! Fortunately (but costly) new gears and sure-grips still available. Mine has new HD Yukon 3.21 gear set with new Mopar Sure-Grip.
 
Last edited:

Mikes5thAve

Well-Known Member
Joined
Mar 3, 2020
Messages
1,375
Reaction score
538
Location
Canada
Look at what rear it has first. A fair number of stock 88 and 89 5th avenues and their civilian dodge and Plymouth counterparts came with 8 1/4. It was unobtanium in other years. Probably just 2.45 or maybe even 2.2 tho.
 

Loy

Member
Joined
Dec 1, 2021
Messages
8
Reaction score
1
Location
Franklin TN
Thanks for the information. The tag on the rear end says 2.7 so it could be worse.
 
Back
Top