Qudra trac

[ab56452001]

Hi all , im a bit confused so please be patient !, my XJ Cherokee's 4wd system i sort of understood , but my ZJ Grand Cherokee has got me lost , i understand its constant 4wd and has a low4wd position on the lever , i presume this is for slow going , mud ,sand etc. On the dash is a 'D' button , im told its to lock the center diff , when would this option be used ? , and can it be used in 4wdh and 4wdl or only low , cheers.

[ab56452001]

P.S. ive google it and gone to about 10 write ups , still dont get it , to me Select trac 1 , Quadra trac , Quadra drive 11 etc.,etc.,etc., all confusing.

[FRANKIDOWNUNDER]

The ZG / ZJ has a constant 4WD, you can only select high range or low range or neutral. The transfer box has an hydraulic coupling that delivers about 75% power to rear wheels and 25% power to front wheels at all times until wheel slip is detected then the coupling delivers most power to the non slipping axle. The "D" button on the dash panel is marked "D off". this locks out the overdrive gear on the Auto transmission, it gives better engine braking when going down hill and better power when towing. There is no centre diff lockup in the transfer box as this is the function of the afore mentioned hydraulic coupling. Hope this helps explain the system for you.

Denis.

[Escapable]

Originally Posted by ab56452001

Hi all , im a bit confused so please be patient !, my XJ Cherokee's 4wd system i sort of understood , but my ZJ Grand Cherokee has got me lost , i understand its constant 4wd and has a low4wd position on the lever , i presume this is for slow going , mud ,sand etc. On the dash is a 'D' button , im told its to lock the center diff , when would this option be used ? , and can it be used in 4wdh and 4wdl or only low , cheers.

Firstly.. my apologies ... it is actually labelled "D" (inside an O) .. inistead of OD ..HA!
ab56452001 - If you PM me your email address I will send you some info (can't past it here) that explains it all and will make sense.

I strongly suggest EVERYONE that owns a vehicle to source an owners manual (they are out there and available) - these manuals explain ALL the secrets to operating one of these models.

For the rest of us: D is the OVERDRIVE On/Off switch and of course the ZJ (ZG perhaps?) has only the Hi - N - Lo lever as it is constant 4 wheel drive and goes where no man has gone before (supposedly) .. but does it with ease compared to the others.. great for touring on dirt!

[turbomart]

The zg or zj in the USA uses a viscous coupling in the transfer case. In 4 high power is delivered to the rear wheels via splined coupling and to the front via a viscous coupling. The viscous coupling locks up progressively when its forced to slip, ie when rear wheel slip occurs.
In low range drive to front and rear is via a splined coupling so no slip is possible, ie the centre is locked.

[ab56452001]

Thanks all for your replies , its helped me understand it now , cheers.

[Doctor W]

Yes, the "D" button is actually "OD" = Overdrive Off.

As for 4Hi and 4Lo .....in 4Hi it (the transfer case) sends Constant(!) 4 wheel drive to both front and rear axles EQUALLY (i.e. 50:50 F:R) via a Viscous Coupling (like a 1988 on Range Rover Classic and RR P38a) ...if either axle starts slipping, the fluid heats up and tends to "lock up both front and rear to prevent loss of drive....the rear axle is a Dana35 type which (in Aussie Grands) all seem to have Trac-Loc -LSD fitted.

In 4Lo drive in the Transfer Case is Locked via splined shafts and the Viscous Coupling isn't used, again drive is sent equally front to rear 50:50.

The rear Trac-Loc LSD isn't great and it can be helped by some concommitant left foot braking to help it do its job.

New Owners Handbooks are available from RockAuto for about $18.00 plus shipping and it explains how to best use the systems on the car to their best advantage.