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1995-2002 Range Rover P38A
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Discussion Starter #1
The goal this year is to get the P38 off pavement at least a few times... be it at a beginner course or simple fire road trails...

I am somewhat new to 4x4 vehicles and am curious about the viscous coupling system on the P38's transfer case. Once traction is “lost” how much time for the gel component inside of the VC to heat up and do its thing? 30 seconds? Several minutes or more? I understand there could be multiple variables at play depending on the terrain and how many wheels have lost traction and such.... I’m just curious if there is an approximation for the amount of time the system takes to engage. Obviously this assumes healthy transfer case internals. I’ve performed the “one wheel test” with a breaker bar and all appears to be in good shape on my truck in this case. The only other cars I’ve had with any sort of locking diffs were a pair of Audi 4000s, and those were vacuum controlled.

Thanks for satisfying my curiosity!
 

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Wheel spin with cause the Traction Control to kick in and that has nothing to do with the VC, it is controlled by the ABS system. If it detects one wheel turning faster than the other on the same axle it will apply the brake to that wheel to slow it down to the same speed. As the front and rear diffs are just standard diffs with no limited slip or locking, that means power still goes to the other wheel on that axle. You'll know when Traction Control doing it's thing as you will be able to hear the brakes pulsing on and off and the TC light on the dash will come on. As a 2002 car you have 4 wheel Traction Control too rather than only on the rear wheels on pre-99 cars. The VC in the transfer case acts to spread the power between front and rear axle and locks almost instantly, in less than a second, when needed (the car can still be driven with only one propshaft attached and the only noticeable difference is a hesitation when pulling away from standstill). So if both wheels on one axle have no traction, rather than a standard centre diff which would allow all power to go to that axle, it locks to allow power to the other axle. The only time you can fool the system is if you floor the throttle on ice or snow as all 4 wheels will lose traction so will be spinning at the same speed.

You'll find that the P38 will be able to drive without problem over terrain that other cars can't, even ones that have been modified for off road use. I did an off road course at Land Rover at Solihull a few years ago (just after the end of P38 production) and the instructors there told me that the P38 is the best off road vehicle they have ever made. The combination of Traction Control, the viscous coupled centre diff and EAS meant it could go places that a Defender of Discovery couldn't.
 

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1995-2002 Range Rover P38A
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Discussion Starter #3
Thank you Richard.

Looking back at my post, I should have used different terminology than “wheel spin”. I had momentarily forgotten about the traction control component working with the 4wd. But thank you for clarifying on how fast the VC reacts when there is slippage in the driveline (maybe that’s a better phrase?). I wanted to get more familiar with what to expect once I finally head off the beaten path... and any warning signs if something is not working as it should. :mrgreen:
 

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1995-2002 Range Rover P38A
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(the car can still be driven with only one propshaft attached and the only noticeable difference is a hesitation when pulling away from standstill).
I wouldn't recommend that, though. You will kill the VC in short order.
 

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That is very true but if you are trying to find a vibration or noise from the driveline it's an easy way of working out from which end. Take one prop off, drive and and it the problem is still there you know it is from the end that is still connected.
 

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1995-2002 Range Rover P38A
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Just start driving offroad than you will understand how she acts.
For VC you will not even feel it is there because as soon as you hit the trail there will be differences between front and rear shafts and VC will start to lock.
Have fun :)
 

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Think of traction control as ABS in reverse. Its uncanny how a P38 can find traction as long as your tires are appropriate for the terrain. If you have street tires in gumbo mud, you will get stuck almost as quickly as everything else. Always a good idea if you are going off the beaten path to pair up with another vehicle and take shovels and tow lines.
 

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I was driving in dirt/sand in Hungry Valley Ca. and on the trails it seemed as I was on the street.
Felt the same. I was impressed. This thread is interesting because I wanted to know more about this subject.
 

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Discussion Starter #11
We do have a sort of “off-road” park here southeast of Cleveland.... used to be called JeepSkool, but ownership has changed over the years. Unfortunately not many Rover folks up by me here. I have thought about the “buddy system” if I do wind up heading out there - we shall see!

The wheels are currently shod with Terra Grappler G2s.... they don’t seem super aggressive, so I’m guessing they’re not the best choice for the real nasty stuff. I do keep some tow straps and such in the truck, but would still rather partner up with someone who knows the ropes better than myself.
 
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