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transfer case rebuild and undercoating

reptile610

NAXJA Forum User
Location
michigan
When I shift into 4L you can hear the chain grinding and spinning but in 4H everything works fine so I'm guessing a rebuild is in order. Was going to do the novak kit unless anyone has a better one?

Secondly while I have the trans and transfer case out I need to replace the rear main seal because it's pouring oil.

Lastly, I wanna do an under coating on it since for some reason it has NO RUST. The dealership wants 200 bucks to do it. Or I was thinking since I have to pull all that anyways just taking a wire wheel to the under side and doing a few coats of rustoleum stop rust and a few coats of rustoleum rubberized undercoating. I did this on a cj amd it turned out pretty goood. Does anyone have any better suggestions for a rebuild kit and undercoating?

99 xj classic with aw4 and np231 located in Michigan (rust belt)
 
You will hear a lot of people say that undercoating will trap moisture and stuff (true if you have rust and undercoat over it)but if you undercarriage is clean and currently rust free I would highly recommend it. If you have any surface rust anywhere grind in down really good, primer it and then undercoat it. $200 is quite reasonable. I had Ziebart do one on my 2009 Liberty and they did a great job plus they also have a yearly inspection and respray if needed.
 
A couple of things. First of all, make sure you really know where oil is coming out, because while the rear main is a likely suspect, so is the oil filter adapter, and the oil often falls into a similar place. The OF adapter can gush out a lot of oil. The back end of the valve cover also often leaks, and air currents push all those leaks to about the same place.

Second, if it is the rear main, it is a two piece affair and can be done without removing the transmission. Fel Pro makes a special one with a double lip to compensate for a worn spot on the crankshaft.

Before getting too deep into the transfer case, make sure the linkage is adjusted right. 4 Low is the first place it will misbehave. The procedure is pretty simple unless your linkage is utterly rusted. Make sure first of all that the linkage is really limber. If you haven't used it much, the bushing through the floor can get stiff. Cycle it about 40 times until it is nice and free. It must be free to move all ways before it can be counted on to engage the TC right.

Then get down under it, and loosen the trunnion bolt on the linkage. Put the lever on the TC into the 4-low position. Make sure the TC linkage has clicked all the way into the 4 low position. Check the shift lever to be sure it is fully into the 4 low position. Now tighten the trunnion bolt. When done, the handle should be pretty nearly parallel to the floor when in 2 high.

If the vehicle has no rust I would not wire brush it unless you need to touch up bare spots with surface rust on them. Make sure it's clean and there's no rust lurking, and either have it done, or even buy some spray undercoating yourself. Undercoating properly applied will not trap moisture and will do lots of good, but when damaged or separated, it will. By all means, undercoat if you can, but once it's done, you need to check periodically for stone damage and raised areas.

The undercoating issue is a well known one for owners (as I once was) of certain old Mercedes. These were done with a fabulously durable and thick undercoating, which kept them rust free for a good 15 years or more. But hidden damage and raising at trim holes lurked, and when it finally failed, it would do so spectacularly - a car rustfree one year would have softball sized holes in it the next. When I replaced the front fenders on mine with new Chinese ones, I bought a couple of cans of spray undercoating and applied them to the brand new clean metal. They remained utterly rust free for over a decade despite their cheapness.

On old, very rusty XJ's I've had good luck with roofing tar, but would not recommend that for a rust free one. Get it done right. Rust free XJ's are a dying breed, and need protection.
 
Thanks for the info guys. My girlfriend's dad is a ford trans tech with 25 years of experience so instead of jumpingthe gun and buying a rebuild kit we'll pull it out and have a look see. I bought yhe jeep about a month ago and had the jeep dealership do an inspection just for $hits and giggles. They said the valve cover, rear main seal, amd crank shaft seal are leaking oil.
 
Also note the Tcase linkage will bind on the guide bearing bolts and one of the bracket mount bolts if the angles aren't just right ... I recently lost 4lo as a result of this. Just going to toss the works and redo the linkage for direct throw instead of pissing around with the "mousetrap" linkage.
 
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