Positraction: 1971-76

["Cadillac Kid" Greg Surfas 15364]

Does anyone out there know who the manufacturer of the "non serivicable" positraction was that was used in 71-76?  Are there any replacements available? Wjhere?
Greg

[bill henry]

I think they were made by Eaton.

[TJ Hopland]

I think I also read Eaton somewhere also.   Never seen anyone offering replacements or repairs.    I had a car with one one time but it didnt work anymore.  Does not seem like it was a common option.   Mine was in a 76 EFI Deville.

[EAM 17806]

HI GANG!  How can we know if our 71- 76 Cadillac Coupe de Villes or Eldorados have this positraction in our cars?  If anyone knows how to tell we would appreciate the info.  THANKS!  EAM

[TJ Hopland]

It was never an option for a FWD Eldorado so that one is easy.  I read somewhere that one of the GMC RV (used the Toronado drive line) places has recently came out with a limited slip.

[bill henry]

my 76 had posi but I never had it apart so I dont know what kind it was

[35-709]

In the old days we could jack up both rear wheels and turn one by hand, if the opposite wheel turned the same way then it was a limited slip rear end (positraction, Safe-T-Track, whatever), if the opposite wheel turned the opposite way it was not limited slip.  Do not know if that still would work on '70s rears or not.  The limited slips also came with a tag, sometimes around the fill plug or under a bolt stating it required special diff. lube because it was limited slip.  If you know the code it should be stamped on the firewall tag.
Geoff N.

[Bob Hoffmann CLC#96]

Geoff,
The first part of your answer is correct. However, positraction info was NEVER on the cowl tag.
Bob

[35-709]

Thank you, Bob --- what I get for making as assumption!   
Geoff N.

[EAM 17806]

GEOFF!  If it never was on the cowl tag then where else was it if any where?  EAM

["Cadillac Kid" Greg Surfas 15364]

Typically if a car has positraction it would be indicated on the build sheet and by the number stamped on the tag /pad on the differential housing.
My original question is "does anyone have any information as to the availability or existence of replacement positraction units for 71-76 RWD full size cadillacs"
Greg

[Otto Skorzeny]

This place sells rebuild parts for Eaton positraction for GM applications.

http://www.drivetrain.com/parts_catalog/positraction/eaton_positraction_limited_slip.html

They also sell positraction units for front wheel drive cars including Eldorado.

http://www.drivetrain.com/parts_catalog/positraction/gm_front_wheel_drive_positraction.html

[EAM 17806]

GEOFF! The way you have described how to check if a 71-76 Caddy has positraction or not is the only way we can tell if it had been installed, per DRIVETRAIN.COM via my telephone call to them.  EAM

["Cadillac Kid" Greg Surfas 15364]

Guys,
Before I asked the question I ran myself ragged going to the normal sources for positraction/lockers/etc.  If in fact they were aware of a limited slip for Cadillacs (71-76) their information was "It was a corporate only rear end and unit".
What I am asking is if anyone out there has actually worked on one of these differentials successfully and if so how did they do it?
Greg

[35-709]

EAM!  It is in your Shop Manual!

According to my '74 shop manual the gear ratios are stamped into the differential, IF the car is equipped with "Controlled Differential", as Cadillac calls it, the gear ratio number is preceded by the letter "G".  Location?  The numbers are stamped to the left of the filler plug between two bolts.  Ratios?  If  you have a 2.93-1 ratio the number will be 3, if you have a 2.73-1 the number will be 8, if you have a 3.15-1 the number will be 5 .  As I mentioned if the car is equipped with a Controlled Differential, these numbers will be preceded by a G.  This is from the 1974 manual, page 4-26!

Geoff N.

[Dave Shepherd]

To this day G designates a locking or posi diff. I think the issue with the ass'y may be the fact that the ring grear is riveted to the diff case, maybe not on the later cars. Back then the diffs were not repairable in the field, they were supplied as remans from Cadillac.

["Cadillac Kid" Greg Surfas 15364]

Dave,
Did anyone try and unrivit, repair and re rivit the assembly successfully?
Greg

[EAM 17806]

GEOFF!  According to the 1976 Cadillac shop manual it is just as you stated above also.  Cadillac refers to these as 'CONTROLLED DIFFERENTIAL" not Positraction at least for years 1971-1976. The manual also states: "The Controlled Differential gear case is serviced only as a complete assembly". All this information is on Page 4-46 of the Shop Manual for 1976. Here is a good explanation from the manual just what the Controlled Differential does:  "The basic advantage of the optional Controlled Differential over the standard differential is that the major driving force is always directed to the wheel having the greater traction.  The unit is not a positive lock type. It will slip before an excessive amount of torque is directed to one rear wheel". Well I guess that settles any thoughts we had concerning how this type of Controlled Differential works on these years.  HAPPY MOTORING!  EAM

[35-709]

Positraction was Chevrolet's term for it, Safe-T-Track was Pontiac's term, I am not familiar with what Olds or Buick called their limited slips. 

The good old shop manual is where I go first.
Geoff

[Dave Shepherd]

I never saw it done in the field, you could not get parts for that type gear set.