Flat Tow Wrangler YJ (Informational - Long)

This is good to know. Thanks for posting.

Could option 4 cause problems? It seems that a true neutral might leave the internal oil pump disconnected.

Where do you get this information? I suspect that some or all of it is false. I can't believe that neutral would lock the axles together, but then again we are dealing with a crappy second rate American manufacturer (this bit is for Stupendous Man).

I have always put the transfer case in neutral, transmission in gear, engine running and let out the clutch before flat towing. This lets me know that the transfer case is really disconnected. Then I shut off the engine, leaving the transmission in gear, and have towed several thousand miles in this fashion. I am sure that the center axle disconnect has indeed been disconnected every time, and that the transfer case has been in neutral, because I never noticed any binding, jerking, suspicious noises, difficulty steering or transfer case damage. Next time I do this, it won't hurt to reach underneath and verify that the front drive shaft turns freely of course.

If you leave the transmission in neutral, it can be driven by a transfer case in neutral because of friction and oil viscosity. This can lead to a dry bearing condition and transmission mainshaft damage. Always have the transmission in gear or park when flat towing.

Earle

You read that in the 4 Wheel Parts mag, eh?

Bill,

I think I have towed mine a total of maybe 3,000 miles. I moved a few times since I bought it. No differentials destroyed yet. I can't perform the test until the weekend, but I sure will do it. In 2HI, you can reach under the vehicle and turn the front drive shaft with all four wheels on the ground. In N it has to be the same way. You don't have to jack up a wheel if you still have the front axle disconnect.

Earle

messagenews: snipped-for-privacy@mid.individual.net...

I think you still need to lift one tire to do the check to know if the driveshafts lock together. For instance, if the front axle is still connected with the engine off (both front on the ground), then the driveshft will not turn with the TC in N. This would make me think (falsely) that the driveshafts are locked together. In order to eliminate the posibility that the front axle is connected, one front wheel should be off the ground.

There are really two things to check: 1) does the axle stay connected with the engine off, and 2) do the driveshafts lock together in N.

It doesn't matter what the cause is. If the front driveshaft won't turn with the transfer case in neutral, then you have problems. I always have the engine running when I shift the transfer case into neutral, because sometimes you have to move the vehicle a little bit to get the gears to mesh, and because I know about the vacuum disconnect I guess. Note that the newer models don't have a front axle disconnect, and that you can still flat tow them if the transfer case has a neutral. I am talking about the TJs, newer Cherokees, GJs, etc. I am only going to do the check because you never know about things, not because I believe that there is anything to the OP's idea.

Earle

Makes sense, if they locked together towed TJ's would be trash by now.

OK, so with my '84 CJ, AMC 20, Dana 300, and NV4500, I should put the t-case in neutral and put the tranny in a gear. Do I need to disconnect the rear drive shaft? Or, what is the downside of putting locking hubs on the rear?

I am not sure that the Dana 300 will oil itself properly if driven from the rear in neutral. You need to get an owner's manual and see what it says. An NV4500 upgrade doesn't really change anything in that respect. For your vehicle disconnecting the rear drive shaft sounds like a good idea. Locking hubs require you to install a free floating axle, which is a good thing, but there is the expense.

Earle

Good discussion on this so far.

I need to note two things:

First, I was researching YJ Wranglers specifically (although we own and tow a TJ in the same manner).

Second, I see that my original post did not copy in (from the file on my computer) my "Sources" information. I herewith correct that fault:

Please mentally add the following to the bottom of my orignal post:

Sources:

1. Petersen's 4Wheel & Offroad, How-To, Beefing Up the NP231 Transfer Case This article was my first exposure to the internals of how the NP231 works and the first place I read anything about how the vacuum operated CAD works. Besides the obvious idea of not starting the engine, this article discusses options 1 and 4 above.

1. Jeep Owner's Bible (Moses Ludel), especially his discussion on how transfer cases work. Also, although I'd learned about backing up to disengage the front hubs, this book is the first place I ever saw it documented.

2. JeepTech, on the web, had a good discussion of the NP231.

1. Many articles I've read in magazines and on the web discuss the towing limitations of the NP231, although most do not mention the mechanism of the locking together of the front and rear output shafts as the culprit. Many articles about Slip Yoke Eliminator (SYE) kits have some brief information about the rest of the NP231 internals.

2. Novak Adapters, online technical articles.

1. RV Net (and some other RVing sites). Lot's of people flat tow jeeps and are very willing to share their experiences.

2. Off-Road Adventures (from 4Wheel Parts); an answer to a question in the Gearhead column actually prompted me to post this note to the list. Some of what I've said comes from Jim Allen (who obviously agrees with the other sources I've read). Any errors remain my own.

Further -on comments in this thread-

Frankly I find it hard to believe myself that Jeep would install a transfer case that would engage the front and rear output shafts together simply upon you moving the transfer case lever from 2WD to Neutral! Of course, I don't know why they used chain drive instead of gear drive either. But in any case, I've read the information about the output shafts multiple times and from apparently knowledgeable people. However, this is always in reference to early NP231 units as installed on YJ Wranglers. I have no idea why this isn't true for TJ's transfer cases.

Despite my own comments in my original post, I acknowledge that DC (and earlier owners of Jeep) always say that if you are going to flat tow to do so with the transmission either in gear (manuals) or in park (autos). I've not had a problem, nor have others who tow with the transmission in neutral. I'm not sure what kind of "fluid currents" would be needed to spin the transmission enough to cause a lubrication problem. However, I'm willing to stipulate that Jeep knows best in this regard. Please mentally correct my original post accordingly. In Gear, that's Clear.

It may have been made clear earlier, but to be complete: it is the rear output shaft on the NP231 that spins the internal oil pump. The commercial adaptors that add 2WD-Low to the transfer case (at least those that result in adding a "true neutral") do not disturb the rear shaft: it still pumps oil while you flat tow.

So stock YJ and TJ owners can: Back up about 10 feet in 2WD, drive jeep to tow vehicle and attach, turn off the engine, place the transfer case in neutral, place the transmission in gear (or park if auto), proceed to safely tow away.

I'm afraid you CJ owners are left to your own devices. NewJ owners are expected to follow the instructions found in their spiffy new manual :-)

Cheers, Ed Humphries Atlanta, Georgia

I did some more looking, and you're right, Earle; at least according to JP magazine's website at

"Flat tow: If your case is in the stock orientation, remove your rear driveshaft from the axle and fasten it out of the way. If you've clocked it flatter than stock, you may get away with the same method mentioned for the Dana 20. Basically, it needs to have at least one gear on the rear output in the pool of oil so it slings the oil around when the Jeep is moving. In the stock clocking setup, this doesn't happen." They also talk about most or all other tcases in jeeps and what to do with them.

Pete