Dana 60 Power Lock installation

[Gimme Jimmy]

I am installing a Dana Power Lock Diff in my '71 GMC 3/4 ton. (original Dana 60)
Do I have to use shorter axle shafts or shorten my oem length shafts in order for the Power lock to work?

[davepl]

I can't imagine, unless there's something really funky about the Power Lock. I know I've never had to change an axle for any other locker/posi.

Are you running into an issue that makes you think you might need to?

[kwmech]

No, same shafts as long as they are 30 spline.

[BCOWANWHEELS]

Yep just pull out the open diff and use the shims on open as a starting point for power lock. If your lucky it will be same as it was when open was pulled. Measure backlash with indicator before dissasembly and resetup to same. Also use setup grease before dissasembly to get r&p gear pattern. I,d at least change carrier bearings and races, check wheel bearings and new wheel seals. Use syn. Lube 80w140 and posi additive from chevy. I,d also replace clutches in p/l if its a used unit. You,ll like it.

[Gimme Jimmy]

Contrary to some suggestions posted on this thread, I have found that the axle shafts used with the "open geared" differential ARE too long for use with the Dana Power-Lock diff. The cross shafts in the carrier are meant to "climb" the V shaped slots in the carrier case. This would have the effect of pushing the cross shafts outward. This Requires some clearance for the cross shafts and pressure plates to move outward toward the ends of the axle shafts. This is normal in the compression and engagement of the clutch plates. The stock (open geared) axle length protrudes to a point just short of the carrier spider gear shaft. This is too long.
I removed the axles from the truck and they were both "polished" on the ends. this indicates that they were rubbing against the cross shafts. (they were not shiny before) indicating that the shafts were too long. Shortening the axle shafts was fairly easy. I used an abrasive "chop saw" (check for squareness) to remove 5/16" from the splined ends. note that the saw blade has some thickness (kerf) and should be included in the amount cut off. The shafts were the beveled (using the bench grinder) all the way around aprox. 45 degrees just past the root of the spline.
the shafts were deburred using some emery cloth and cleaned. I installed the gaskets and axles and torqued the flange bolts. I test drove the truck and noticed the rear axle was quieter and some of the "chatter" gone. formerly I had assumed the "chatter" was normal on tight turns as the diff had new clutch and pressure plates. The chatter has been minimized and is now quieter.

[BCOWANWHEELS]

I dissagre completely. I,ve installed 40-60 of these in d60 & d70,s with 0 modifications and 0 trouble. jmo

[Gimme Jimmy]

Shortening the axle shafts on the Dana 60 power-lock was necessary to allow the Power-lock to work as it should. The shafts were the same
stock shafts that I removed. from the truck. Granted, the Dana-Spicer parts list show only one part number for both open geared and power-lock diffs, but in this case there was interference. I removed about 5/16" from the splined ends of the axle shafts. Probably 3/16" would be plenty in most cases.
This procedure only applies to the Power-Lock differential as it is the only application (that I know of) has moving cross-shafts and can create a clearance problem like this. This procedure is also unnecessary if the axle shafts are not shiny or galling on the tips. This is a positive indication that the shafts are too long and are impairing the operation of the Power-Lock.

[kwmech]

I completely disagree also. I've been building axles..... regular repair and custom builds.... for over 35 years. Never had to shorten an axle b'cuz I put a posi or a locker in. The only issue I can think of that would cause this problem you are dealing with is bad spindles where the inner wheel bearing has been grinding on the spindle due to too much preload. But even then, the damage would have to be severe enough that you'd have to junk the whole housing