Limited slip

[Loboheeler]

Found out from the production codes my 1996 5.0 AWD has a limited slip rear axle. I assume this a Traction-LOK unit with clutches. How long do these last, and is there any way to test for function? You can't turn a wheel with the trans in neutral with the other wheel on the ground, so I assumed the clutches were holding to some degree. Add some friction modifier, or just change everything?

 

[1998Exp]

I believe that the way to check is in Park, with both rear wheels in the air. If you are doing this with one wheel on the ground in Neutral, you are trying to turn the driveshaft and rotate the front wheels through the viscous clutch in the transfer case, so you are not checking the right thing.
The manual has a minimum spec for the torque at which the clutches should release (20 ft-lb if memory serves), so if you are curious, you can check that.

As for the oil, I would just change it. Synthetic is more expensive, but probably worth it. At least some brands of those (Royal Purple comes to mind) contain the friction modifier already.

Found out from the production codes my 1996 5.0 AWD has a limited slip rear axle. I assume this a Traction-LOK unit with clutches. How long do these last, and is there any way to test for function? You can't turn a wheel with the trans in neutral with the other wheel on the ground, so I assumed the clutches were holding to some degree. Add some friction modifier, or just change everything?

 

[shucker1]

With proper care they should last at least 100K miles or more. Sever service will shorten their life.

Like 1998Exp said. Both wheels off the ground in park. If you can't rotate either wheel they are good.

If you decide to change I would recommend the FMS Carbon Fiber set.

I did mine and I get a lot better bite but it is a little more noisy around corners.

Chris

 

[koda2000]

Find some sand (just a little) on a road or in a parking lot. From a dead start, punch it and see if both wheels spin on the sand. If they do the clutches are still working. You can also jack both rear wheels of the ground and put the trans in neutral. If you then spin either wheel by hand the other wheel should spin in the same direction. If it does the clutches still working, but they may be weak.

At 100K it would probably be a good idea to change the fluid. You'll need 3 quarts of full synthetic 75W140 hypoid gear oil and Ford LSD additive. To reseal the cover I recommend Permatex Ultra Black RTV and follow the directions on the tube.

 

[1997XLTRollover]

I run Amsoil synthetic 75-140 and add half a bottle of friction modifier or more as needed. Every truck is a bit different. Just listen to see if you get clutch chatter. Far as clutches wearing it depends on how much your truck was beat on but I doubt they're worn out. My F-150 has 236k miles and will still do a brake stand and spin both tires no problem. Granted it has a 9.75 so those tend to last longer, but still I would expect at least 150-200k out of the 8.8 limited slip.

If you do replace the clutches I don't recommend the carbon packs on the ex unless you're building a drag/off road rig on the cheap (read: if you're not putting in a true locker). I run them on my Mustang and I agree they are great, grab much better, but they also wear out much much faster. So unless you have a true need for a better gripping pack, use factory stock replacements, they last much longer.

 

[Varsity]

I did what I THOUGHT would be a cheap way to re-gear and threw a junkyard 4.10LS axle in with ~250k miles. When all was said and done, the truck was in neutral up on jacks, and both wheels spun in the same direction. I thought it was working, and it was, but it was super weak, just like koda said. Turned out needing a full rebuild since there was so much wrong with it. Apparently the only thing not destroyed on it was the ring and pinion surprisingly. Dodo move on my part.

I'd try both ways mentioned here. If it all checks out, you should be good

 

[Loboheeler]

Thanks for the tips! My only experience with a Traction-LOK was one put into a Ranchero with 9" rear which did have some clutch chatter on turns the way it was set up. Moved that to an Econoline Motorhome and it was fine with the increased weight.

What is the maximum power transfer between the two wheels in a well functioning unit? The reference to 20 ft. lbs. is pretty weak.

 

[1998Exp]

What is the maximum power transfer between the two wheels in a well functioning unit? The reference to 20 ft. lbs. is pretty weak.

I don't think that power means much when you are trying to get moving on a slippery surface. Power is the product of force and speed, or torque and rotational velocity. When your speed is zero, power is zero, regardless of how hard you are pushing. What counts in this situation is torque. Still, 20 ft-lb is lame; probably around 5% of what the engine can deliver to the wheel in first gear and 1000 rpm. Perhaps the 20 ft-lb that I quoted from memory is wrong. Anybody?