artieb

I was wondering if someone could explain how the vaccuum and wiring work with the fork to disconnect both front stub axels? And are they problematic? Thanks for helping me find the truck I want! Thanks, Artie

mortis_9812v

The wiring is a sensor if im not mistaken, been a few months since ive last been in one, and the vacum lines activate a shift fork which engages the two axles much like a transmission shift fork does. I know alot of people who have had to replace them, the actuator is what went out and me and most people end up just buying an aftermarket one instead of replacing with a stock because they are about as expenseive unless you go to a wrecking yard. I found one at a wrecking yard for $25

mortis_9812v

The actuator is what actually moves the fork.

Crimedog

Yep, you've got two vacuum lines going to the actuator. One pulls the shift fork into the 4wd position, which slides a collar over the two axle shafts. The other is activated when in 2wd, it pulls the collar all the way over to one shaft so they can rotate at different speeds. The wires you see coming out of there is just a switch that turns your 4WD light on when the collar is slid over to connect the shafts.

stikineriver

look at a thread i started 2 weeks ago "no 4x4 anymore" Lots of info and a couple links

TheBigNasty

4x4 posi lock is a great fix. love mine. also allows for use of low range without engaging the front axle. The vaccum actuator is not necissarily problematic...just junk.

artieb

Thanks, and what happens is that the servo only separates the axel on the passengers side only, while the drivers side rotates, spinning the spider gears? Trying to understand all I can before I buy one.... Thanks, Artie

TheBigNasty

Correct...the drivers side axle goes straight into the differential where as the passengers side has 2 axles connected by a collar. There is an outer shaft, that is what you see connected to your stub shaft (the shaft that goes from the u-joint to the wheel) , and an intermediate shaft that runs from where the CAD housing is into the differential. There is a collar that is moved by a fork connected to the shift actuator inside the CAD housing which locks the outer shaft to the intermediate shaft. Under normal 2wd conditions the drivers side axle spins with the wheel and through the spider gears spins the intermediate shaft in the opposite direction (just like if you spin a tire on a rear axle and the other one goes the opposite direction). Because the collar is not connecting the axles this is possible and the front driveshaft does not spin...the intermediate axle is as far as the power is transmitted. When you shift into 4wd vaccum is applied to the shift actuator pulling the collar in to the locked position. This is possible while the truck is moving because the delay it takes for the actuator to move is longer than the time it takes for power from the t-case to spin the driveshaft up to wheel speed and stops the intermediate axle from spinning in the opposite direction. Because the drivers side alxle is always transmitting power to the differential lockers or posi-trac units are not recommended because you will cause the driveshaft to always be locked in, even no engine power is being transmitted....this causes accelerated wear on the front drivetrain and possible vibrations. Soooo....this might be confusing but read it a couple of times and if you still don't get it feel free to ask any more q's you may have.

TheBigNasty

P.S. I don't like using paragraphs.