[crozzer]

Took the '02 Overland to Hollister yesterday. Good lord these things are fun. The guy in the Range Rover was more than a bit peeved when I blasted up Truck Hill on the first try after watching him spin and slip and flail, and ultimately back down.

They all wanted to know - "Is that thing stock?" Yep, heated leather seats, great tunes, and all.

I only just stopped short of letting them know I had it in cruise control on the way up the hill

So, here's the question:
Is there a definitive test for measuring the effectiveness of the front diff? I think it is worn beyond what it should be, so that the torque transfer is both delayed and not complete, and that it should be replaced.

More on that: I got into some stuff at Hollister where one wheel would be way off the ground, so I'm needing the torque transfer to the other wheel instantly and fully. On my Jeep, the QD system and the Vari-Lok f/d in particular seemed to be way short of transferring torque instantly and fully to the stopped wheel. In my case, repeatedly, it was more like one wheel in the air, spin a second or two, then spit some dirt out of the stopped wheel, then spin the airborne wheel a couple of seconds, then spit some dirt... I tried a few different throttle variations from slow and creepy to modest, to, umm, aggressive (the HO was helpful with this last attempt...)

I also hear a light metallic grinding noise from the diff when I back up and turn. And the freeway-speed (or, shall I say, faster than freeway speed?) humming is much more prominent now than it was 20,000 miles ago.

I want to get it warranty-replaced!
My dealership says they don't have a test for that, and so they can't see that it is broken, and so they won't replace it. That's like saying, yeah, the engine is weak, but we don't have a dyno, so we can't measure it, so we can't fix it...
I need a test or a spec, or a...

(Oh, and thanks in advance for the recommendations to upgrade to lockers, spools, and other fun stuff, but I bought this daily driver specifically so I could experience the dual personality of this system - road friendly AND trail dominant.)

[Wheelin98TJ]

Originally Posted by crozzer

...I think it is worn beyond what it should be, so that the torque transfer is both delayed and not complete, and that it should be replaced.

More on that: I got into some stuff at Hollister where one wheel would be way off the ground, so I'm needing the torque transfer to the other wheel instantly and fully. On my Jeep, the QD system and the Vari-Lok f/d in particular seemed to be way short of transferring torque instantly and fully to the stopped wheel. In my case, repeatedly, it was more like one wheel in the air, spin a second or two, then spit some dirt out of the stopped wheel, then spin the airborne wheel a couple of seconds, then spit some dirt... I tried a few different throttle variations from slow and creepy to modest, to, umm, aggressive (the HO was helpful with this last attempt...)...

The torque transfer does take time so no worries there.

DC exaggerates when they say QD is capable of transferring almost 100% of the power to the tire with traction. I've never seen one actually perform like this is the real world.

Originally Posted by crozzer

...My dealership says they don't have a test for that, and so they can't see that it is broken, and so they won't replace it...

The FSM explains the test procedure. Way to go dealer service dept.

Vari-Lok Differential Test

1) make sure fluid level is up to bottom of fill hole
2) with the TC in 4WD full-time position drive in a tight circle for 2 minutes at 5 mph to fully prime the pump
3) shift TC in 4WD low position and put transmission in PARK
4) block the tires on the axle not being tested so that the vehicle won’t move
5) raise the axle to be tested so that both wheels are off the ground
6) rotate the left wheel by hand as fast as you can while an assistant rotates the right wheel in the opposite direction
7) the left wheel should spin freely at first and then increase in resistance within 5 revolutions until the wheels cannot rotate in opposite directions
8) the Vari-Lok differential has engaged properly if the wheels stop
9) after stopping for a moment, the fluid pressure will drop and the wheels can be rotated again


If its inoperative, the whole assembly needs replaced. DC does not sell rebuild parts for the Vari-Lok diffs.

[txtumbleweed]

Sounds to me like your QD is working about the way it was designed to. It does require some wheel spin to engage and keep the torque transfer going. Here is a short version of how to test the individual axle for side to side transfer. (It was posted by another, but missed the name).

(1) Make sure that the fluid level is correct.
(2) Transfer case in 4WD Low and transmission in Park
(3) Raise both wheels on the axle to be tested
(4) Rotate one wheel rapidly (1 rev per sec) while an assistant rotates the other wheel in the opposite direction
(5) The first wheel will rotate freely at first and then the resistance will increase within 5 revolutions until the wheels cannot be rotated in opposite directions simultaneously for a moment
(6) After the momentary stop, the fluid pressure in the differential will drop and the wheels can be rotated again.

If you do a search on "Quadradrive test" you will pick up a few good discussions.

I would definitely get the "light metallic grinding" looked at while it is under warranty.

[crozzer]

WOW! Thanks for the FSB info guys! I have been to three (!!!) dealerships, asking this same question, and not heard anything so useful as what you have shared here. Thanks!

[crozzer]

Anyone have the FSM info on testing the NV247 tsfr case? Same principle - I want to be sure the clutch packs, gerotor, etc. are working full strength in my tsfr case, too.