Limited slip rebuild
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There has been endless discussion at Thedieselstop.com about the worthless
Ford factory limited slip differentials. As I've researched solutions for this problem I've noticed Dodge owners
also complaining about their TracLok differentials as well. The consensus seems to be that as trucks become more
trendy people who wouldn't normally drive them complain about the characteristics of a proper limited slip, so the truck
manufacturers have made the limited slips less effective to cut down on unnecessary service visits and complaints.
I added Amsoil synthetic oil to my differential, and it helped a little bit...but the limited slip still doesn't work
like I think it should. The limited slips in my Trans Am, Jeep CJ7, and my old GMC truck will spin both tires. The
Ford won't. The Ford limited slip works under very light loads...just enough to appear like it is working. But when
you need it it will let you down. I've gotten stuck in wet grass and backing around in my snow-covered driveway.
There are several aftermarket differentials available for the Ford Sterling 10.5" axle. These cost several hundred
dollars and require setting up the gears...which is a pain. I'm gonna try to rebuild the factory limited slip into
something respectable. That would be the cheapest and easiest way.
Here is an axle clutch plate. The splines of the axle fits through these plates and they turn with the axle. Here is a housing clutch plate. The 'ears' on these plates fit into a groove on the differential housing, and they turn with the housing.
When one wheel is spinning and the other wheel is stationary, the differential housing is spinning half as fast as the spinning wheel. Because of these differences the clutch plates in the differential start binding with the axle clutch plates. In a properly operating limited slip the clutches bind, both wheels turn, and hopefully the vehicle becomes unstuck. For some reason the Ford limited slip clutches start to bind up, but then release and become ineffective.
When I tear into the differential the first thing I'll be looking at is the order of the clutch plates.
The normal order is axle plate - housing plate - axle plate - housing plate, etc...this gives the differential the most 'bite'. However,
people are finding axle and housing plates grouped together. This allows for more slippage and a less effective
limited slip.
I also purchased a set of clutches and shims (P/N F75Z4947AB) from
Ford Parts Cheap for $81 plus shipping. I couldn't find any aftermarket
supplier who had these. In addition to putting the clutches in the correct order I might add a shim or
clutch to each side to make the differential 'tighter'.
Here is a good tutorial on differentials.
I expected the kit to include the clutch plates, but I was pleasantly surprised to find the kit also included belleville washers, a selection of shims, and two bottles of friction modifier. Here is the packing list. Stay tuned as I find the time to tear into the differential.
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