1997 Dodge ram 1500. When put in 4x4 mode, the rear wheels lock up, like they are dragging. Checked front and rear ratios, both are same. Tires are all the same size. Transfer case has no fluid. Could it be the plantery gears in the transfer case or something else?

 

i don't know. does the rear drive shaft lock up in both 4-High and 4-Low?

when the rear locks up, what's the front drive shaft doing? outputtting power, or is it locked up also?

the rear output shaft is active in both 2 and 4 wd, so it doesn't make sense to me that it would lock up in 4.
its seems more likely that the front is what's locked up, and since the rear is hard-coupled to the front, that the front problem affects the rear output.

several things could lock up the front. gears, chain, bearings.

 

+1 on that. The mainshaft design on your np231 and most other transfer cases does not allow for disengagement of the rear output, so whatever the rear is doing in 2wd, it is doing the same in 4wd.

Look to the front. Also don't drive your truck without vital fluids

 

The transfer case has no fluid.......

I think that tells the story right there. I would take a close look at the case, and see if you can figger out where the fluid went. I am going to bet your case is cracked, if not holed somewhere.

 

LOL.

i'd give these nice folks a call. $700 + $100 shipping both ways. about 1-2 hours to swap out and you're back in business.
i ordered on friday and had it monday afternoon about 4pm. they're not far away from me though, so i guess that's cheating.

http://www.transfercases.com/

 

I dunno... sounds like the R:P ratios are mismatched to me. Are you dead certain they're the same? Put the thing on four jack stands and run it in 4WD. If the rears turn freely then, your ratios are mixed.

 

The thing I forgot to say, that when the truck is on the lift the 4x4 works fine but when the truck is lowered to the ground its locks up

 

Seems like mixed ratios. Pull the diff covers and verify the ratios. IIRC, it should be stamped on the ring gear.

 

Or turn the driveshaft with one wheel anchored and one free. However many spins it takes to turn the wheel one full rotation, multiply that by 2, and you have your ratio.

 

I cannot think of anything except mixed ratios that would cause that. I'd go so far as to say that unless there's some kind of really exotic breakage that by all rights should have blown the transfer case apart already, only mixed ratios could cause that. And will blow the transfer case apart before too long if you use 4WD before the ratios are matched.