[Fairfax 944]

I'm looking for a shop to fix/replace the rear differential in my truck.

My 2002 F-350 tow vehicle also serves as my snow removal vehicle. It has never seen as much snow as we had this weekend. Even with mud and snow rated tires and 4X4, I got stuck 6 times. Only one front wheel was spinning, and one rear wheel was spinning. The rear has a factory limited slip, but it appears to be shot. (I know the front is an open diff)

I'm looking for a shop, preferably in the northern Virginia area, that specializes in differentials. I likely will install a Detroit brand Truetrac Torsen rear differential by Eaton, but maybe the factory one can be rebuilt for a lot cheaper.

I'm having a real hard time finding a shop that really knows differentials and specializes in them. Of course, any shop will say they can do a rear diff, but there are some tricky adjustments that need to be just right, and if they are not, the rear end will whine, or prematurely wear out. The parts alone run over $650 for a new Torsen diff, and the one labor quote I got so far takes me to $1,400 for the job. Ouch! In searching, I found an Internet listing for a shop that will rebuild the factory diff for $600, including all parts and labor. Only problem is that this shop is in San Francisco. http://www.rearendspecialties.com/in...s/Page1880.htm

I'm tired of relying on our new Ford Flex to pull out my truck. Does anybody know of a shop that specializes in differential work?

[smdubovsky]

IIRC the truetrac torsen is like a quaife. Put two wheels on ice and you still won't be able to get out. The factory unit is clutch based. I can light up all four of my rear wheels in 2wd mode I know alot of folks used to put torsens in the front as it doesn't affect steering manners like a clutch or locker would.

[Fairfax 944]

Originally Posted by smdubovsky

IIRC the truetrac torsen is like a quaife. Put two wheels on ice and you still won't be able to get out. The factory unit is clutch based. I can light up all four of my rear wheels in 2wd mode I know alot of folks used to put torsens in the front as it doesn't affect steering manners like a clutch or locker would.

You are correct that a torsen differential will not apply any torque when one one side of the differential is completely free of any resistance. However, a light application of the brake pedal is supposed to provide enough resistance to transfer power to the wheel with traction.

Anyway, if I could find a shop to rebuild my factory differential, that will likely be good enough for me. For a new Eaton limited slip differential for my F-350, the cheapest price for that is $719, just for the diff. Then I need differential carrier bearings, etc. which takes me up to about $1,600 - $1,700 with labor.

[smdubovsky]

Originally Posted by Fairfax 944

However, a light application of the brake pedal is supposed to provide enough resistance to transfer power to the wheel with traction.

Yeah, thats how the H1s worked.

[Richard Curtis]

Jim... call my friend (and ace mechanic) Dave Planakis at Hartwood Automotive in Fredericksburg, 540-752-2300 and ask him who he recommends, if he himself can't do it (it's 45 minutes from your house to his shop just off I-95). He's very helpful. He's also one of the most knowledgeable mechanics I've ever known.

[Fairfax 944]

Originally Posted by Richard Curtis

Jim... call my friend (and ace mechanic) Dave Planakis at Hartwood Automotive in Fredericksburg, 540-752-2300 and ask him who he recommends, if he himself can't do it (it's 45 minutes from your house to his shop just off I-95). He's very helpful. He's also one of the most knowledgeable mechanics I've ever known.

Hi Richard, thanks for the info. I'll call him tomorrow morning.

Originally Posted by smdubovsky

If you can buy the clutch discs, it might be an easy DIY. We've rebuilt E30 LSDs and its only a couple hr job.

I've seen the DIY's for replacing the truck differential. It might be easy if you've done it before, but there are several things which need to be installed with extreme precision. Like anything else, it's easy after the first time. But, since nobody I know has a lot of differential experience and failure to do a proper install could result in a failed differential on the road, I'm inclined to leave this to the pros.

[smdubovsky]

Originally Posted by Fairfax 944

I've seen the DIY's for replacing the truck differential. It might be easy if you've done it before, but there are several things which need to be installed with extreme precision.

Not replacing, repairing. If you don't have to take the ring gear off the carrier you don't have to reset the pinion depth. Thats the tricky bit of replacing any diff. In the E30 you can open the end of the carrier & get the clutches & spiders out w/o disturbing the ring. The only tricky part is getting the shallow headed bolts off w/o tearing them up. Don't know if a ford diff comes apart a similar way or not.

[hoophead]

Originally Posted by smdubovsky

If you don't have to take the ring gear off the carrier you don't have to reset the pinion depth.

Why would removing the ring gear reset the pinion depth? Is there something different about the E30 diffs (I've never opened mine up)? The ring gear should still be centered on the axis of the diff when you put it back, so how would the pinion/ring gear alignment along the axis of the pinion change? The Porsche manuals say that you don't have to reset it if you replace the differential housing - implicit in that operation is removing the ring gear and bolting it to the new one. New ring gear and pinion, yes. New housing or side plate, yes (although side plate is borderline IMO).

[smdubovsky]

Originally Posted by hoophead

Why would removing the ring gear reset the pinion depth? Is there something different about the E30 diffs (I've never opened mine up)? The ring gear should still be centered on the axis of the diff when you put it back, so how would the pinion/ring gear alignment along the axis of the pinion change? The Porsche manuals say that you don't have to reset it if you replace the differential housing - implicit in that operation is removing the ring gear and bolting it to the new one. New ring gear and pinion, yes. New housing or side plate, yes (although side plate is borderline IMO).

Removing the ring gear and reinstalling it on the SAME carrier does not require resetting the pinion depth. Removing the ring and putting it on a DIFFERENT carrier requires all the special tools and pain of resetting the depth.

Its not the ring being colinear w/ the carrier axis of rotation thats the problem (thats inherent when the carrier is machined on a lathe). Its the side-to-side location. If the ring moves further from the center line of the pinion, the pinion must move closer to the centerline of the ring to keep mesh constant. And visa-versa. Depending on machining depth, bearing thickness, preload, etc the carrier can be moved side to side. That needs to be compensated for.

You say the porsche manual doesn't require resetting it when swapping carriers? (Like non-lsd to lsd.) I don't see how that can be. Every lsd install requires resetting the R&P.

[smdubovsky]

If you can buy the clutch discs, it might be an easy DIY. We've rebuilt E30 LSDs and its only a couple hr job.