Need rear axle enlightenment
 

Was checking codes in a glove box on a 67 1/2 ton and found one with a listing of JO4aa SP44 G87 power lock with 3.54 gears.Then it specifically listed apart number of 3903545. So I am assumming it was some kind of special order rear end. I understand the positraction but what is the differences between that and NO-spin and Power Lock ---codes below

G80-Positraction
G86-No spin
G87-Power Lock

Re: Need rear axle enlightenment
 

A question for longhorn man.

Re: Need rear axle enlightenment
 

it's a dana 44, the power-lock was only for spicer axles. i have seen a few other 67 (and earlier) 1/2 tons with a d44 rear. usually gmc's.

Re: Need rear axle enlightenment
 

I agree. Its a Dana 44 (the sp44 stands for spicer 44).
3.54 with powerlok, a clutch type posi unit for dana/spicer rears.
I have a 68 GMC C15 with a 396/TH400/dana44 3.54 (build sheet verified).
It could use a posi rear (hint, hint!).

I will go out on a limb here and guess that you could only get a Dana 44 rear in leaf spring configuration? Anyone have any evidence of a D44 coil rear?

Re: Need rear axle enlightenment
 

longhorn man knows nothing about this... and, that 3.54 gearing is a totally new one my me.

Re: Need rear axle enlightenment
 

Found this old post and could not find any other on the subject. But the 67 GMC I am working on has the sp44 3.54 ratio but has J04AB on the spid and part number 3903540 with a 305 v6. Just wondering would this be posi[traction or no spin and what is the difference?

Thanks Russ

Re: Need rear axle enlightenment
 

The different names are a result of the branding by the different manufacturers for a clutch style limited slip differential (LSD). So a Power lock and a Positraction LSD are both the same thing but for different axle brands. And adding to the confusion a Dana 44 in a GMC had a Power Lock but a Dana 44 in Chrysler had a Sure Grip.
Even among the various GM brands there were different names for the same limited slip units. Pontiac called theirs Safety-T-Trac, where Chevrolet called it Positraction, and Oldsmobile named theirs Anti Spin.
Then throw in 10 bolts that have cone style LSD and 12 bolts that are a clutch style, and depending on which piece of factory literature you refer to both styles may or may not have the same name. No wonder it can be confusing.
And all that was before the aftermarket got involved. Whew!
The link has more information.

https://en.m.wikipedia.org/wiki/Limi...p_differential

Re: Need rear axle enlightenment
 

Thanks for the clarification, very good information.

Thanks Russ

Re: Need rear axle enlightenment
 

I'm going to split hairs a little with the Positraction being the same as the PowerLock. Yes, they are both clutch type limited slips. The Dana diff is a 2 piece case that has "ramps" in the case that increases the preload on the side plates with power application. Probably the best clutch type LSD ever.

3.54 gears a very common ratio in Dana axles. Was the stock ratio in big block powered trucks with Dana 60 rear.

Re: Need rear axle enlightenment
 

I always thought the no-spin was a detroit and the others were either a power-loc or an eaton