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So I’m putting new diff covers on the Wag and it looks like someone put some kind of LSD in there - it has an LSD lube tag, and the wheels spin the same way. Is there any way to identify it without taking the gears apart? Here’s some pics.

It appears to be a Spicer trac-lok. They aren't terrible but they aren't great either. It's a constant-bias friction clutch limited slip. It has some spring washers that apply pressure to a clutch pack. Once the difference in resistance between each axle shaft overcomes the static friction if the clutch pack, it allows differential wheel speed. The 2 reasons it's not great is that the static friction torque threshold is almost meaningless compared to the weight of a big old steel truck, and once it wears out (since you can't feel it do anything anyway), it lets the spiders slop around until they jam and shatter.

You're ahead of the curve knowing that you have it! Most of the tracloks I've seen blown up happened when the owner didn't know they had an lsd. I wouldn't swap in a trac-lok, but I wouldn't bother with replacing one if a found it in my axle. Be sure to use an LSD friction modifier in the gear oil and run it until you want something else.

Thanks! I am planning on a real locker for the rear eventually, but I was working under the assumption this was just an open diff. I haven't checked the front yet, but eventually I was thinking either a mechanical (no clutch, all gears) LSD, or another locker up there too. For now though, I'm pleasantly surprised to find this in there.

The clutches may well be worn out, which means it will act like an open diff. But adding friction modifier will help it to work like it should.

Just keep in mind a lunch box style locker won't work with a trac loc carrier.

Locked and Loaded wrote: ↑Tue May 12, 2020 4:57 am Just keep in mind a lunch box style locker won't work with a trac loc carrier.

Good point. To add a locker, it needs a full carrier replacement. Either an open carrier with a lunch box, or a full carrier locker like a detroit or ARB.

I doubt any PO would put a trac-lok in the rear and then something better up front(I'm pretty sure it's factory). If he wants a lunchbox rear, he could flippy-flop the front & rear carriers. While you can't lunch box a trac-lok, you can Lincoln a trac-lok, which is really the best thing to do with a trac-lok for both traction and toughness.

Yeah I wasn’t going to go lunch box - probably ARB (on board air has additional advantages. I’ve already thought about maybe putting this up front when that happens. Thanks for the help guys.

Another question - as you guys can see, the fluid hole, or whatever it’s called, is a good bit higher with the new cover - should I still use the normal amount of lube or add more to get it right up to the hole?

I have those SOLID covers on two FSJ--love them. No, dont fill it to the bottom of the new hole--it will be over filled and likely push oil out the vent. I use a piece of wire bent at a 90 to set the fluid level close to the original. Make sure to let the oil roll out to the axle bearings and then final fill.

Thanks

I'll recommend a Truetrac for the front. I had one in my W350 with 44 front. Highly functional on the street with great snow manners.

Those covers with the higher hole are intended for a front high pinion D44. There is a version with a lower hole. And some covers with two, so they work for high or low pinion.

rocklaurence wrote: ↑Wed May 13, 2020 5:30 am I have those SOLID covers on two FSJ--love them. No, dont fill it to the bottom of the new hole--it will be over filled and likely push oil out the vent. I use a piece of fortnite hoodie wire bent at a 90 to set here the fluid level close to the original. Make sure to let the oil roll out to the axle bearings and then final fill.

thanku for this!