4x4 engage solenoid ????

[rjwest]

The Solenoid( black thing on the front axle) that engages the hubs to the drive line.....

What is the differance between 1996 and 2000???

Can a 2000 part be made to work on a 96???

[Uncle Wally]

Somewhere in that timeframe between those years, they changed the solonoid from a system that uses a gas that is heated and expands to push the piston to engage 4X4 to one that uses an electric solonoid to push the piston. In order to use the late model unit you need the actuator, the puck that goes in the axle before the solonoid does, and an updated harness that you need to splice in to the current setup. There are several different harnesses depending on your truck. If you talk to a GM Parts guy, you should be able to get a copy of the update from him. (that's what I did.)

I updated mine when I had the engine out (the splice ended up being on the harness right above the transmission. I originally recieved the incorrect harness for the solonoid and determined it wasn't correct by trying to figure out where the splices were suppose to go (this harness required two splices). That was rectified in short order with a phone call. It would have been a pain to do it with the engine/trans installed. Although I believe it could be spliced somewhere else that is easier to get to and still operate the same. I just didn't worry about it since it was easier to not trace the wiring out in the truck.

The only advantage I see is that it engages a little faster then the previous setup. Although I believe if someone had a new gas style actuator it would be almost as fast. I think the issue came about because the gas eventually leaks out over time/use.

Waldo

[gunner 6165]

Uncle Wally the biggest advantage to changing from the gas actuator to electric is that the gas actuator can disengage unexpectedly, ie: water crossings, driving in deep snow, etc, if it's cooled externally. I had a 93 full size Blazer and had the front axle disengage while trying to get home in about 8 inches of snow. Unwelcome surprise to say the least. :eek:

[rjwest]

Uncle Walley , Thanks.

Here's my problem. When driving at a no load
condition, The truck feels like it is pulling
back, IE something in drive train is " grabing,
in a somewhat cyclic mode,

I have checked the engine controls on the Laptop,
Fuel rate , waste gate, etc are normal,( no real
changes in parameters )

Checked everything underneath including new universals.

History:::!!!!!!!

Replaced rear gears with 3.73.

Had a front unit from a 2000 k3500 with 3.73

Work was done at a 4x4 shop, They did not know what to do with the different solenoid harness
( Different plugs ) so they swaped the right
side housing and axle stub. Assured , no problem..

Result:
96 solenoid and stub housing on a 2000 asm.

I am begining to think that 0ne side of the
front shaft is in 4x4 mode and causing the
" binding. I have noticed a loss of MPG also.
and when backing up in sharp turn, one wheel
has a tendency to jump, like when in 4x4 mode.

I do not know how front axle of 4x4 works":
IE: both axles free or just unlocked from each other. Do you have any thoughts/advise:

Going to have a "speak at " with the 4x4 shop this morning......

Thanks....

[rjschoolcraft]

The front axle disconnect on these IFS trucks is simply a slide collar on the right axle output shaft. When disengaged, it decouples the right axle shaft from the stub shaft coming out of the carrier. With the transfer case disengaged, the pinion is stationary. The left axle shaft does not decouple; therefore, the left wheel will drive the spider gears through the left axle causing the right stub shaft to rotate backwards. The right axle shaft rotates frontwards (since it is still connect to the wheel through the CV joint flange).

When four wheel drive is commanded, the transfer case engages and begins to drive the pinion/ring gear. This causes the right stub shaft to slow then begin to rotate forward. When the stub shaft speed equals the right axle speed and the spline teeth align, the slide collar moves to the left to lock the stub shaft to the axle shaft... and you have four wheel drive.

Obviously, the side gears and spider pinions are in motion while driving in two wheel drive. This means wear is a much bigger concern than with normal four wheel drive units or with other differentials. It is imperative to keep the oil level up in the front differential housing on the IFS trucks. I found this out the hard way and had to replace the carrier on my Suburban last summer.

I'm not sure what mixing halfs of the diff housing will do. Why didn't they just swap the actuator?

[Uncle Wally]

It sounds like the transfer case is engaged and the front axle is disconnected. Like described above, it would only drive one front wheel. On my truck, I can pull the cover off the side of the T-Case and see if things engage/disengage in the T-Case. You need to twist and distort yourself pretty good along with use a mirror, but it can be done. I'm not sure if you have the same T-Case though.

Waldo

[rjwest]

Well, talked to the 4x4 mech,
He doubts front axle is a problem, Thinks it is
possibly a rear hub out of round ???

Going to put it on lift and rotate/balance tires,
And also run it in gear to see if anything is out of wack....with drive train, 4x4 unit.

Thanks for the info, and description of how the front unit works.....