Topic: Why is Part Time 4wd there on the XJ? (Read 11544 times)

MWF · « **on:** November 07, 2007, 11:00:59 AM »

Call me silly but why on the XJ do you have the option of part time and full time 4wd? Rather than just have full time 2wd and full time 4wd?

The Smiths · « **Reply #1 on:** November 07, 2007, 11:50:10 AM »

Full time 4wd can be used on the road because centre lock is not engaged.

Part time 4wd is only for use on loose surfaces because front and back wheels are locked together and hence rotate at same speed

MWF · « **Reply #2 on:** November 07, 2007, 12:02:55 PM »

I see, I was kinda hoping that's the case.

So you can basically lock the centre diff by selecting part time?

UKJeeper · « **Reply #3 on:** November 07, 2007, 01:44:06 PM »

No 'basically' about it. Thats exactly what you'd be doing.

greggmo · « **Reply #4 on:** November 07, 2007, 05:36:46 PM »

yup. part time is exactly that, use only on lose surfaces.

if you use it on the black stuff you will brake things including your wallet.

garyf · « **Reply #5 on:** November 07, 2007, 06:53:29 PM »

I will try and post some photo's of a transfer box from a Cherokee that I bought recently where the owner had driven it in part time going round the M25 at 80mph, the transfer box is in 3 pieces and definatly not repairable, oh also the propshaft tried coming through the floor pan as it departed from the rear axle, will try and post photo's later.

greggmo · « **Reply #6 on:** November 07, 2007, 07:05:18 PM »

cool. we like carnage photos.

Dave69 · « **Reply #7 on:** November 07, 2007, 07:59:43 PM »

the last prop shaft i saw that tried to come through the floor was on a ldv van, the prop let go went through the floor and destroyed the gearbox entirely. Prop testing later with a chequer plate reinforment saw the prop let go at 5.5k rpm with 10gms of inbalance. this punctured the rear wheels on the one side and threw the front timing belt off as the engine torque unloaded. this was done on a dyno for safety. the driver at the time was scared 5h1tless then we found out why, the van had been converted to lpg and there was a nice big hole in the heat shield and a gound in the tank.

another good day at the office

MWF · « **Reply #8 on:** November 08, 2007, 08:39:44 AM »

Out of interest though if you are off-roading in full time 4wd and things get really slippy, is there any advantage in switching to part time 4wd?

garyf · « **Reply #9 on:** November 08, 2007, 08:29:01 PM »

This is what hapens when you leave it in part time 4X4 and try driving round the M25 at 80mph, must admit I don't mind I bought the Jeep very cheap after it happened, his loss my gain!! :lol:

Bubba · « **Reply #10 on:** November 08, 2007, 09:04:08 PM »

almost as bad as a double carden joint getting heat sieze at motoway speed :roll:

greggmo · « **Reply #11 on:** November 08, 2007, 10:58:12 PM »

ooops

Mik · « **Reply #12 on:** November 09, 2007, 11:14:14 AM »

Quote from: "MWF"

Out of interest though if you are off-roading in full time 4wd and things get really slippy, is there any advantage in switching to part time 4wd?

Yes.

In 'Full Time' if any of your 4 wheels loses traction then you lose all drive.
In 'Part Time' it requires either front wheel AND either rear wheel to lose traction for drive to be lost.

This excepts any contribution made by a Limited Slip Diff of course.

Mik · « **Reply #13 on:** November 09, 2007, 11:17:40 AM »

Quote from: "UKJeeper"

No 'basically' about it. Thats exactly what you'd be doing.

Wearing my 'Senior Pedant' hat, selecting 'Part Time' doesnt lock the centre diff. It simply doesnt use it thereby 'locking' the front to the rear.

MWF · « **Reply #14 on:** November 09, 2007, 11:42:16 AM »

So Mick, would you recommend using Part Time 4wd when actually off roading and then just using for Full Time 4wd for on road or mixed use?

tag · « **Reply #15 on:** November 14, 2007, 07:15:36 PM »

Hmm. so weres the center diff in a 231 part time 4wd?

JamesH · « **Reply #16 on:** November 14, 2007, 07:57:26 PM »

There's no centre diff in a 231, it's either rear wheel drive or front and rear axles 'locked together' four wheel drive. Mik may have a proper Tech explanatio if you need more.

tag · « **Reply #17 on:** November 14, 2007, 08:05:57 PM »

yeah exactly! reading the thread they mention locking the center diff, i've stripped and repaired a 231 all it does is connect drive to the front through a chain, with a gear selector to give you high low and no drive.............

Bubba · « **Reply #18 on:** November 14, 2007, 08:14:22 PM »

part time is there to confuse you ...and it does

crofty · « **Reply #19 on:** December 18, 2007, 09:52:22 AM »

Right, so if I've got this right, my 2.5 diesel has selections for:

2wd (rear)
4wd high (part time light on)
N (neutral)
4wd low (part time light on)

and if I use either 4wd setting on a relatively grippy surface I'll break something because the front and rear wheels are locked together, hence rotating at the same speed.

I therefore realistically have only 2wd on the road.

Is that right?

Mike Pavelin · « **Reply #20 on:** December 18, 2007, 10:04:48 AM »

Yup, that's about the size of it.

crofty · « **Reply #21 on:** December 18, 2007, 10:27:22 AM »

Whoops. Don't think I've broke it, only spent about 15 mins in 4wd, and only at fairly low speed.

The Smiths · « **Reply #22 on:** December 18, 2007, 11:50:44 AM »

Quote from: "crofty"

:oops: Whoops. Don't think I've broke it, only spent about 15 mins in 4wd, and only at fairly low speed.

You'd know about it if it had broke :lol:

Bigmadgregor · « **Reply #23 on:** December 18, 2007, 12:39:14 PM »

I was getting confused about this topic... My 96 XJ (like crofty) only has a part time light that comes on when 4WD hi or lo is selected, I have never seen a full time light. should i have this option? and if not why not? sounds a bit crap to have a 4wd mode that you can't use on tarmac without breaking it? So i'm basically pumped if i want to drive in 4wd in icy or snowy conditions on tarmac?

sorry if this is a stupid question but I'm just learning... :?

JamesH · « **Reply #24 on:** December 18, 2007, 05:16:38 PM »

If it has a 2.5 diesel or petrol engine then it is basically 2wd on the road. The 4.0 came with a different transfer case that does allow 4wd on the road. Snow or ice can be dealt with by using the shift-on-the-fly ability of the case, allowing you to shift into part time 4wd if it gets really slippy, while still moving along. Full-time 4wd is a better option in my opinion though.

Author Topic: Why is Part Time 4wd there on the XJ? (Read 11544 times)

MWF

MWF

UKJeeper

garyf

MWF

garyf

Mik

Mik

MWF

tag

tag

crofty

Mike Pavelin

crofty

Bigmadgregor