Engine/Transmission (1998.5 - 2002) Drivetrain binding

[AFoulk]

I probably should have asked this question earlier in winter when we had snow on the ground, but here it goes. This winter when we had snow, anytime I'd take a turn in 4wd, I could feel the truck kinda jumping like the drivetrain binding up. It didn't have to be a real tight turn either. Is this normal? I replaced both front axle u-joints when I did my ball joints and all my drive shaft joints seemed to be in descent shape yet. I'm wondering if who ever had the truck before me changed one of the axle gear sets and got the ratio slightly off. I thought if they were off, it would cause a lot more noise and jumping though. How far off do they have to be to cause problems? I wish I would have realized it had this problem when I changed my axle fluids, that woulda been the perfect time to check my ratios. Also, my truck is supposed to have the factory LSD in back, but when I give it hell in the rain while turning, I can't get the back end to jump out like maybe its an open diff. But when I jack the rear up and turn one wheel, the other one turns the same direction. Any ideas? I put Royal Purple in both axles and thats supposed to have the additive in it for the LSD. Should I try some friction modifier anyways? Sorry, I realize that was a little long winded

 

[NHelmer]

as far as the binding, were you in snow or dry? How sharp was the turn? All of my trucks have been 4wd. This is normal unless you are in really sloppy mud or on ice. All of your wheels are pretty much turning at different speeds, especially front to rear. The inside front has the least distance to travel and thus should turn slower and the outside right has the farthest to go and thus should turn the fastest. However, you are in 4wd and they are all trying to turn the same speed. This is why they bind and should only be used in a straight line (drag racing) or on slick surfaces. Hope this makes sense and helps.

 

[AFoulk]

I figured it would bind say turning from a dead stop at a traffic light, but it'll do it around some moderate turns too. Its hard to describe the turns with out pictures I guess. I had a jeep wrangler before my truck, and it would bind up around tight turns, but they all do that cause of the short wheel base. I figured a truck with a wheel base like mine shouldn't have a problem. And it does this in snow and slush, not just on dry pavement. A buddy of mine has a 98 just like mine, and he gets some binding too, but not quite as bad as mine. Years ago, my dad bought an Inter. Scout II and drove it off the lot in the snow. Didn't even make it a mile down the road and it would jump, give a loud crack and jump outta 4hi. He took it back to the dealer and they found that the front tires were worn more than the rear ones. They shaved the rear ones down to match the fronts and he had no more problems. I figured if my gears were off slightly, it would act similar to that, but all I get is a little binding.

 

[AFoulk]

oh, and I've also driven chevy, ford, and dodge 1/2 tons and never experienced this problem. I just figured it was the nature of the beast with these trucks, but I just wanted to get somebody's opinion on it.

 

[jkalchik]

Should be the nature of the beast, and your Wrangler (NP231 tcase) should have behaved the same.

What's happening is that in 4wd, your front and rear driveshafts turn at the same rate. If you're moving in a straight line and your tires are all the same size (as you note in #3,) there should be little if any binding. Once you begin to turn , the rear end will naturally track inside the front end, and thus the driveline will begin to bind up.

 

[AFoulk]

I was just worried cause we have a couple 4wd chevy's at work, and I've never experienced any kind of binding with with them. My jeep was actually the rubicon model, so it had the NP241 in it. That thing would bind really bad when you were at full lock trying to do donuts in the snow. That was probably the front axle u-joints causing that. But man in 2wd, you could get that thing to spin on a dime! Sometimes I miss it But then I take my cummins for a spin and I feel better

 

[AFoulk]

Any ideas on my LSD? I've only got 77,000miles on the truck so I can't imagine it would be shot already. Should I try adding some friction modifier to it or is whats in the Royal Purple enough?

 

[jkalchik]

I was just worried cause we have a couple 4wd chevy's at work, and I've never experienced any kind of binding with with them. My jeep was actually the rubicon model, so it had the NP241 in it. That thing would bind really bad when you were at full lock trying to do donuts in the snow. That was probably the front axle u-joints causing that. But man in 2wd, you could get that thing to spin on a dime! Sometimes I miss it But then I take my cummins for a spin and I feel better

No, it *WASN'T* the front u-joints causing that. An NP241 is a 4:1 instead of a 2. 72:1 tcase, and it is built heavier than an NP231. Otherwise, they work the same. Any time you you turn both front and rear driveshafts at the same rate (locked tcase, center diff, what ever you want to call it,) you'll get driveline bind. If you locked the diffs in your Rubicon, it'll bind up even more as it binds left and right as well as fore and aft.

As far as the Chevies go, that'll depend on whether or not those would lock the front and rear driveshafts together.

 

[SnoKing]

Any ideas on my LSD? I've only got 77,000miles on the truck so I can't imagine it would be shot already. Should I try adding some friction modifier to it or is whats in the Royal Purple enough?

To test this go to a parking lot and do figure 8's. If you get a lot of jerking, then add a little friction modifier, drive a bit to mix it in and repeat the figure 8's. You want just enough to stop the LSD from grabbing. Too much and LSD becomes ineffective. SNOKING

 

[AFoulk]

I didn't have the t-case of my Rubicon in 4LO when I was doing the donuts though, and I didn't have the lockers engaged. Only time I got the binding in that was at full steering lock (wheel turned all the way), thats why I figured it was the front axle shaft u-joints binding up on that. Snoking, I'll give the friction modifier a shot.

 

[jkalchik]

Are you *NOT* listening? Where did I say anything about 4lo?

Anytime you're sending equal power fore and aft, you're gonna get a driveline bind. How much is apparent does depend on what surface you're on, but it DOES HAPPEN.