Ok i been searching and cant seem to find the right answer. like the title says, 93 4x4 5speed. I converted to manual hubs and have constant vacuum to keep the ADD in the engaged position. I want to flat tow about 500 miles each way behind my motorhome. If I put the transmission in N leave the Tcase in 2HI and unlock the hubs, I dont see a need to remove the driveshaft. Please educate me on why or why not.

Thanks

 

Toyota doesn't recommend it. The theory is that much of the lubrication of the transmission depends on the input shaft turning, which doesn't happen when flat towing in neutral. You risk oil starving and damaging the output shaft bearing. For similar reasons you can't put the tcase in neutral and safely flat tow. In addition, with the tcase in neutral the vehicle is still in 4wd, so the front and rear drive shafts are tied together and both rotating.

Best is to pull the rear drive shaft at the differential and tie it up securely. A bit of a hassle, but only 4 bolts and a lot less trouble than changing out the tranny.

Your fronts will be fine with unlocked manual hubs. (Unlocked ADD is also OK for flat towing.)

 

I posted this response in the other thread you asked this question in, I'll copy and paste it here, it tracks with exactly what RJR said.

I've never towed my 4runner, but it was towed quite a bit before I ever had it.

I believe the rear drive shaft does need to be disconnected to do it properly. My runner has a rear drive shaft disconnect mechanism right between my driver seat and trans tunnel.

I assume it was aftermarket, but I've never really looked into it. I'll try to snap some pics of the pull knob and the actual mechanism under the truck.

 

Not that I would ever doubt RJR, but the recent 4runner manuals are pretty clear: https://www.toyota.com/t3Portal/docu...f/OM35B37U.pdf (page 192). Apparently that's called "dinghy towing," and Toyota says you should not do it.

Remco sells a drive shaft coupling device. http://www.hitchsource.com/remco-dri...u-p-30332.html It has to be welded to the driveshaft tube (Remco will make it up for you). And it's kinda spendy. If it were me, and I was talking about 2-10 trips/year, I'd just get a pair of wrenches, a piece of carpet, and some baling wire.

 

To satisfy myself, I did more research into the internals of the R series transmission. The transmission is basically "splash lubricated" by the rotation of the counter shaft being partially submerged in oil in the bottom of the transmission. The counter shaft only turns when the input shaft is turning. So, if you are flat towing in neutral, you have no counter shaft rotation, thus no splash lubrication, and the output shaft is running high and dry at 3500 rpm or so for 500 miles. Not good. Don't do it.

An alternative if you want to use the 4runner as a run-about during your trip, and don't want to be connecting and disconnecting the drive shaft multiple times per day.
1) completely remove the rear drive shaft and stash it inside the 4runner.
2) Hook up to motor home and unlock the front hubs
3) Tow to wherever
When you need to drive the vehicle
5) Lock hubs
6) Put in 4 hi
7) Drive away in front-wheel drive.
When ready to dinghy tow again, simply hook it to the motor home, unlock the hubs, and continuing towing.

This will work until you need 4wd for something, in which case you'll have to re-install the rear drive shaft.

 

thanks for the replies, RJR I like your idea of pulling the driveshaft and going FWD just to get around and then put the shaft on at my destination.

 

just for clarification, is it ok to leave the ADD in the engaged position and the hubs unlocked?

 

If your rear drive shaft is disconnected, and the front ADD is inactive the rear diff is self lubricating and thw only pary suject to lubrication concerns. Fwiw the owners manual details this sort of thing, from what I remember it says to stop every XX miles and run the engine for YY minutes, or trailer the vehicle.

 

Yes. If the hubs are unlocked, nothing but the front wheels are turning while you are towing the vehicle. The CV shafts, front diff, and front drive shaft are all stationary, so no possibility of lubrication issues.

Basically, with rear drive shaft off and front hubs unlocked, your drive train (other than the rear diff) thinks the vehicle is parked in your garage. The rear diff will be turning, but it's no different than normal driving. It will be just fine.