85 c10 rear axle options

[Dave C.]

I have an 85 C10 that I use as a summertime street cruiser.  It has a fresh small block and a 200 4r tranny.  The rear end is the original 10 bolt with a 2.73 open.  I like the gas mileage, but I would like a two wheel peel.  What carriers and gears work with the truck 10 bolts?  Are they the same size as the 70-81 f body 10 bolts that run a 8.5" ring?  I can cut and weld tubes if need be, and I have a friend who can set the lashing on a gear set.  I am just trying to see what my options are.  Any advise is appreciated.

[Irish_Alley]

i "think" you will see a slight drop in mpg with a locked rear since you will be turning both axle shafts = more resistance

[Da67goatman]

No change in mpg as long as you don't regularly 2 stripe test your posi lol.  I'm also going to add that you need to match your carrier to your ring and pinion and to your axle shafts.  I don't know much about 10 bolts but theres probably a carrier break somewhere between high and low gears and probably several different spline counts for axle shafts.

[nlauffer]

If you buy new, you are probably looking at $600-$900 for a posi unit, ring & pinion gears, and install kit.  The posi unit can be found from a few different sources but I have seen most around $500.  Ring & pinion gear sets can vary widely depending on brand.  Same with install kit which are your bearings and shims. 

I don't know what vehicles came with factory posi units, but there are a couple posts on here about this.  I just bought a 92 C1500 SWB 4.3V6 5 speed.  I was told it has a 3.73 posi.  I haven't checked axle code so I don't know for sure, but a truck like this would probably be a good place to look for a used one.

[Captkaos]

There is a split in the spline count on the 10 bolts so make sure you get a carrier that matches.  The trucks are 8.5", the rest of the 10bolts should match.

[Dave C.]

Thanks guys for the input.

I have access to some 8.5" carriers and gears for ten bolts that came out of cars.  I'll have to get some bearing measurements and check out the splines to see if anything I have will match up.  I just did not want to waste the time if they were completely different like the 12 bolts car vs. truck.

[75gmck25]

The factory limited slip differentials used in these trucks is a Gov-Lock, not a Positraction.  In general, a Gov-Lock is designed for better traction on slippery surfaces (e.g., mud and snow) and it will not hold up well when frequently laying two stripes on asphalt.  This article provides a little more explanation.
http://www.ringpinion.com/technicalhelp/ContentFrame.aspx?FilePath=~%2FContent%2FParts%2FPositractions%2F%2FAn_Improved_Eaton_Positraction.inc

Bruce

[Captkaos]

Positraction is GM's Marketing Name for limited slips.  Gov-lock is Eatons name for their limited slip.  Trucks prior to around 1976 used clutch type limited slips..

[Greybeard]

Maybe consider a Detroit (Eaton) brand locker http://www.eaton.com/Eaton/ProductsServices/Automotive/DifferentialsLockingDifferentials/PCT_338161 One of these could turn out to be the best of both worlds. They offer a little for of everything there.