4Crawler

iTrader: (3)

How the system works:
- http://www.off-road.com/trucks-4x4/t...tem-19259.html

Two basic vacuum connections at the axle actuator, one to lock and one to unlock and one vacuum line connecting the engine intake manifold to the ADD switching valves. One can guess the way to proceed.

4Crawler

iTrader: (3)

Correct, you can still shift on the fly "if the front hubs are locked". But if the front hubs are unlocked, you have 2WD, period.

My point was that some folks think that manual hubs and removing/disabling ADD stuff = "no shift on the fly", but that is not the case.

The only thing you lose is that if you have hubs unlocked and you want to shift into 4WD, you will have to manually lock the hubs that first time, unlike with ADD you can shift into 4WD most any time.

alfio

right, makes sense

right, also makes sense.

personally, i've never had a problem with ADD failing but i would be willing to 'sacrifice' the convenience of ADD for sake of simplifying things on my truck and gaining a stronger axle. that would be why i will eventually get rid of the ADD stuff. in the mean time, manual hubs will do.

93blackrunner

I did the hub swap, and still no 4wd. Does the relay have to be good for it to work?
I'm thinking I have a problem in the t-case. Any ideas or advice would be great.

scope103

I'm guessing you think that everyone knows what "the" hub swap is. I sure don't.

I'll guess that you replaced standard (ADD) always-locked hubs with manually lockable hubs. Yes, if 4wd didn't work with the hubs locked, it will still not work with the hubs manually locked.

Yes, the relay has to be good. And the VSVs, the vacuum lines, the transfer case, and all of the myriad parts discussed in the scores of postings in this thread. You can bypass some, replace some, and fix any of them. Then you would have 4wd.

Why don't you spend a few minutes reading the posts in this thread. Then, if you still have questions, someone here will be willing to help you.

93blackrunner

I've gone through pages and pages of questions. Anything to do with 4wd. Multiple forums. I've done the diag myself. I'm not a super tech by any means, but I know what I'm doing.
I had an intermittent functioning vsv. Was told I could put manual hubs on, and lock the actuator fork, and sleeve in 4wd to bypass that. Seems to be working, the hubs engage, the front driveline will turn as long as the rear wheels push the fronts. 4wd light doesnt come on at any point in time (switch replaced). Read on identifix that there are occasionally problems with the valve body in the transfer case. Anyone else experience this, or anything similar.

scope103

Lots of different transfer cases over the years. I'm going to guess you have the A340H transmission (because you're talking about valve bodies). That transmission has diagnostics for the solenoid in the transfer case. http://web.archive.org/web/201408161...31diagnosi.pdf

Have you jacked up the front to confirm the wheels and front driveshaft always turn together? Have you confirmed that the front driveshaft will NOT turn in 4Hi with the rear driveshaft not turning? Just eyeballing the front driveshaft while you roll the vehicle may not be enough; a little friction in the system can turn that driveshaft even though nothing is engaged.

The 4wd light is driven by a switch inside the front diff; is that the switch you replaced? That switch should close if the actuator fork is in the "engaged" position.

As you can see, I've got to make a lot of guesses here. If you could describe what you've done, why you did it, and what diagnostics you've run, someone is likely to be able to help you.

(BTW, seems like a lot of work to avoid fixing an intermittent vsv.)

rrowlandrramos

DeathCougar

iTrader: (23)

rrowlandrramos

rrowlandrramos