Hi I'm new to the forum and need a little advice/help. Vehicle is a 2000 4R SR5 4wd 3.4L. The 4wd is the J-shift. Currently the 4wd is not engaging. The light does come on and stay a solid green and i believe low engages. The testing i've done so far is with the vehicle on jack stands, put it in 4hi, I see the front driveshaft spinning but neither cv shaft spinning. On the inboard side of the driver cv, the larger round part of the cv kinda just shakes up and down. The vacuum on the add actuator switches properly but havent been able to test how much vacuum it gets. Could this be a bad cv shaft or a problem in the diff? Also, when driving there is no rattling noise like i'm used to with cv shafts going bad.

 

Sounds like a diff problem. It's possible for a CV shaft to get that bad, I'd have to guess (all three tripod bearings sheared off?) but I can't imagine it not making horrible noises.

AFAIK the solid green light means that the ADD mechanism on the front has successfully moved into 4WD position, a limit switch in there turns the light on and off (with the transfer case switch as well).

With everything stopped/off (obviously) what happens when you grab that shaft and wiggle it around? If the middle part of the shaft moves around but the inboard doesn't, bad stuff is happening with the shaft. If the inner part moves up and down as well, bad stuff is happening with the diff - that part splines into the guts of the diff and should be very secure and not wiggling.

If you start swapping the diff, take off that shaft first and it should give you some clues.

PS: Swapping the front diff is more difficult than it looks. It's really tucked in there between the crossmember/steering rack/oil pan/etc.

 

alright so I've gathered some more information, i picked a vacuum gauge and the add actuator is receiving a good amount of vacuum, with the add removed i manually moved the collar into the locked position. I left the 4wd shifter in 2wd so i could still turn the driveshaft, at this point i should have been able to turn the driveshaft and see a wheel turn. This worked about half of the time. When it was not working the only thing moving was the driveshaft, no part of the cv's were moving. So that leads me to believe its a problem in the diff, what part could it be? are splines somewhere sheared off somehow?

 

Likely to be some teeth gone on the ring and pinion.