front diff longevity?

on the same old girl (91 Z71), what is normal to expect on the front diff?? I shift into 4x4 religiously to keep things moving....the 4x4 light no
longer comes on (understand its simply a switch?) after a bit of a delay (not much) 4x4 does come in and work normally.
I've always had a bit of transfer case hum when in 4x4 at higher speeds, and a trans shop said not to write home about it till it explodes.
However...the other day at the dump I shifted into 4x4 at coming to the base of a hill...I guess it decided to wait till I was climbing the hill to go into 4x4 and I got a "clunk". no big deal, but what was that????
Also, its prolly about time for a front diff engagement solenoid. somebody listed the gm part numbers to do the electric motor upgrade (the motor itself and a harness to retrofit). can someone re-iterate?
any thoughts on what other peoples front diffs are doing on early 90's chevy's? I just want to know mines not doing anything abnormal (and about to explode).
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you actually don't need to do that, with a central axle disconnect system like our trucks have, the passenger side (if memory serves) axle always turns with the wheel causing the spider gears to spin, stirring the gear lube around.
the 4x4 light no

it's actually a thermoelectric actuator, basically there is a heater, some gas and a piston. the heater causes the gas to expand and push the piston to engage the driver's side axle. GM says that 30 sec engagement times is completely normal. the actuators are quite failure prone.

if it's noisy, check your fluid levels, your front diff can be quite loud when low on gear oil.

the clunk means that you had a tire spinning and the axles were equalizing their speed. in most cases it's not a big deal, but don't hold the pedal to the floor and yank the lever. that'll send the chain out through the side of the xfer case.

actuator p/n:26060073 harness p/n:12376316
however you need to check with a parts dept on the harness as there are several part #'s available.

just keep them full of fluids and you should be fine. my 88's front diff is doing fine, other than a weeping seal. you will LOVE the electric actuator. the engagement is instant and firm.
HTH, Bret
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