I've got a problem with the 4wd on a '95 Chev 1500 Reg cab, auto transmission, 350 CID engine.

The 4wd worked just fine the other night, pulled her into 4wd in a wet pasture day before yesterday and had no 4wd.

Yep, got stuck and had to seek assistance from a F*rd PSD

Put it up on ramps this morning for a little investigation and found nothing obviously broken, The shift lever and linkage seems to work ok. (when you shift it low range and neutral work fine) when the shift lever on t-case is in 4wd position the front driveshaft cannot be turned by hand, spins freely when in 2wd.

ANyone have any experience with these things??

Advice where to look and troubleshoot??

Thanks.

Sorry for the Chev question.

 

There is a vacuum operated shift mechanism on the front differential that is notorious for going out either by leaking, sticking, etc. If that is the problem, don't replace it with vacuum parts. Buy a Posi-Lock kit that changes it from vacuum to cable operated and will it not give problems.

 

I think Solaryellow is right about the axle disconnect but I'm not sure if Chevy uses a vacuum actuator. They used an electrical actuator a while back that had all kinds of problems especially when it was cold. Either way fix the actuator or replace it with the fool proof cable setup.

 

Thanks guys. I'm 99.9% positive the problem must be the electrical disconnect. Anyone know how it comes apart, what it looks like and if it can be fixed?

(the disconnect must be electric as there are wires but no vacuum lines going to the front dif.)

p.s I was wrong the truck is a '90 not a '95.

WOW that truck is in good shape for it's age.

I believe the part in question is called a thermo actuator??

 

Camelracer is right about it being electric. I was thinking of another vehicle a friend of mine had that was vacuum. Either way it's a troublesome part. Buy the cable and keep it lubed up and you'll have no problems. The electrical disconnect is a part that the GM dealers here still keep in stock because it is such a problem. I think the cable system is cheaper than buying the electrical disconnect. Don't hold me to that though.

 

The thermoactuated ones I've seen on chevy's use a heating coil to heat and expand a fluid that pushes the actuator. If the moon is in the right position and the stars are lined up correctly and it's not too cold you may have 4wd. Go with the mechanical system.

 

Had same prob with my 95 suburban last winter---ordered a "4X4 Posi-Lock" kit from summit so it is manually actuated now and just LOVE it. It costed about the same as OEM, but its a one time deal, and now I can us 2 wheel drive LOW range without front end pulling.