Below is all I can find about it. I'm looking at a 89' with towing package and Dana 44 and NP242. The seller mentioned it's a "posi". What does that mean? Old school clutch type posi? Just wondering if it can be removed and upgraded with ARB, 35-spline, etc. I haven't decided so this is just a question of "can I" not "should I". Thanks.

Dana 44 non c-clip - 30 spline, 1.31" diameter shafts, 8.5" ring gear, 2.75" axle tube - used 87-89 on some(not all) XJs equipped with towing package.

 

Took me an hour to figure out it's called a Trac-Lok. Knowing the name helped a lot in the searching. One thing seems clear, I can expect it to be worn out. So the question that remains, is it just a carrier swap or is there some tiny difference in the housing that prevents putting in an ARB or Ox. So far Google search turns up almost nothing. Although I read something that slightly implied it's the same housing with or without a Trac-Lok.

 

Clutch pack. Rebuild kit is about $75. Trac-Lok is a very "street friendly" limited slip, but not so good offroad, and the clutch discs grind down to complete uselessness in about 50K miles.
You can swap in another brand, PowerTrax, etc make drop in replacements.

 

You can install whatever locker you like.

Eaton E-Locker FTW!!

 

Thanks for the info. Let's call it an education because even though it had a tow package it still had the D35 rear. Sad. Still had low miles and dirt cheap so I bought it anyway.