Dodge Nitro 4x4 big problem with 4WD lock!!

[19jacobob93]

Just went for a ride with my old man in his 2008 Nitro (same vehicle as the last Jeep Cherokee)
He stuck it in 4WD mode because he hasn't done so before and wanted to blow out the cobwebs as some 4wd systems are prone to siezing if unused
It wouldn't engage properly and made a loud whurring sound when driving coupled with a serious knocking/thudding sound when we went round a corner and the car wouldnt steer more than quarter lock! Also the car vibrated like crazy when in park or neutral.
We put it back in 2wd and it still wouldnt steer at first but after 5-10 seconds of driving it started working fine again.
This problem is only with the 4wd mode so what could it be? Is it a common problem because i cant find much doing searches online

 

[bvance554]

What type of surface were you on? Pavement?

 

[Chris142]

Originally Posted By: bvance554
What type of surface were you on? Pavement?
x2. not ment to be engaged on hard surfaces ....ever!

 

[19jacobob93]

1st time we tried it was on grass, tried it again on the tarmac after and same both times. Seems like the surface wouldnt be the problem, more the 4wd system is screwed. Had other 4x4s for years doing the same thing at the same place without a problem

 

[Oil Changer]

Really? So I have to stop using four wheel drive during my winter commuting?

Originally Posted By: Chris142
Originally Posted By: bvance554
What type of surface were you on? Pavement?
x2. not ment to be engaged on hard surfaces ....ever!

 

[Shannow]

With the centre locked, the front and rear driveshafts are locked together. which means that the front and rear ring gears MUST turn at exactly the same time. Problem is that the tyres are all different diameters, and as you turn corners, they all turn at different speeds.

This "winds" up the drivetrain components to the limit of traction, which means that the torque on each axle, universal, clutch etc. is exactly the same as if each of the 4 wheels was doing a "burnout" (more actually, as the tyres are probably at low levels of slip, not spinning.

That's why everything feels tight...and why often, you have to back back a few metres to unwind it all before you can unlock.

The big problem is that if you do that at speed, the torque times the RPM mean that you have a thing called "circulating power"...the apparent power through the ground/tyres/diffs can be many many times that which the engine puts out (it can't pull a 4 wheel burnout, but that's the sort of power running through the drivetrain). The engine only has to provide enough power for the speed, and the frictional losses in the drivetrain...

it can and does burn out diffs, fatigue axles and CV/Universals.

If it's on gravel, snow, sand etc., then the limit of traction is very low, and the circulating power low, and that's when they are designed to be used.

Dry pavement and locked centre 4WD is a recipe for broken parts.

 

[Chris142]

Originally Posted By: Oil Changer
Really? So I have to stop using four wheel drive during my winter commuting?

Originally Posted By: Chris142
Originally Posted By: bvance554
What type of surface were you on? Pavement?
x2. not ment to be engaged on hard surfaces ....ever!
if your winter commute consists of pavement or hard packed dirt...yes.