On a GV (or XL7) the front axles are always rotating.
When you engage 4WD, drive to the front wheels is engaged inside the front diff.
In 2WD disengaging the front wheels with manual hubs will stop the axles rotating.
This should give you;
- reduced wear on the diff axle seal (prone to leaking)
- reduced wear on the CVs
- slight improvement in fuel economy due to less drag (small)
If you have a lift then you probably want manual hubs to reduce stress on your CVs as they will be operating at greater angles than standard. Also, if you 'do' your CVs then you can disconnect the axles and drive out in 2WD
Manual hubs from any of the 1.6 litre Vitaras (up to 98) will fit a Grand Vitara (98-05) or XL7 (00-05).
Coily Sierra hubs will also fit
Give them a clean out and lube with a smear of grease
Most wreckers should sell you a pair for $80-120
Older hubs often have not been engaged for some time and probably have dirt mixed with the grease locking them either on or off so you may have to dismantle them, clean and lube with a smear of Molybdenum disulfide grease (Castrol LMM is one)
It is a good idea to fit new 2 x O-ring (part number 43838-60A00) at base of hub and 2 x gasket (p/n 43813-60A00) between hub body and cover with knob. I paid $9.06 each for o-rings and $6.17 each for gaskets (May 07)
A complete new manual hub (p/n 43800-60811) is $465 per hub!
If you try to engage 4WD high 'on the fly' without your hubs engaged then you will hear noises from the front diff as the axles are not rotating at a similar speed to the driveline. Not recommended if you want a long life out of your diff.
As per the standard Suzuki recommendation for manual hub Vitaras; engage the hubs at least once a month so that the axles and CVs change position, lube the diff seals and balance the wear.