Actually, I have two problems with my truck and for which I'd like advice.
The first is that when I brake I feel a pulsation in the truck and brake pedal. The pulsation is not apparent when the brakes are not applied. And, the pulsation only occurs after several miles of driving with regular stops. The pulsation goes away if I drive highway speeds for 20 minutes or more without using the brakes and returns after using the brakes for a few stops. I assume the problem is with a brake component getting warm or hot from braking and becoming warped. More on this in another post, but, I think the pulsation is coming from the driver's front brake.
A more immediate problem was discovered while in the process of trying to identify which wheel was causing the pulsation. I put the truck on stands so all 4 wheels were off the ground removed the front wheels, put it into 2wd and pressed the accelerator and brakes at the same time so as to warm up whatever component appeared to "warp" under heating. In 2wd, no pulsation (although one rear wheel seemed to engage a bit sooner than the other).
I then applied the emergency brake and no pulsation. So, I don't think it's the rears at all.
I then put the truck in 4wd high and allowed the brakes to drag against while the accelerator was depressed. After a short while, I felt the pulsation. AHAH, I said. It must be the front disc brakes which are pulsing.
Then I noticed that with 4wd-hi on only the driver's side hub (wheels were removed) was spinning (perhaps more evidence that this was the offending wheel?). The passenger side front hub did not spin when the truck was in 4wd-hi or low. Rather, it seemed to want to start spinning (to engage) but would only start to spin and then stop (even though the brakes were not applied and the other hub and the rear wheels [wheels still mounted in rear] was spinning freely).
Also, when I took it out of 4wd-hi the driver's side hub continued to spin for some time. I had to put the truck into 4wd-lo and then take it out of 4wd-lo and back into 2wd for the front, driver's side hub to stop spinning.
By the way, the 4wd light comes on on the floorboard display when the
4wd is engaged (either hi or lo) and after about 15 - 20 seconds.So, I seem to have a problem with the engagement of the front axle. I've read that there are some problems with the stock, heat-activate actuator. And, I've read the TSB's on replacing the heat-activated with electro-mechanical ones that engage and disengage immediately. I've also read that the electro-mechanical actuator is only recommended as a replacement for the heat-activated actuator if the GVW is not 8500# or above.
So, here's my questions.
Firstly, are the symptoms I describe above consistent with a problem with the 4wd actuator? Please consider in your responses the fact that one hub spins in 4wd but the other does not.
Secondly, does the spinning of one hub and not the other suggest that the actuator is working but that there is another problem with the 4wd unrelated to the actuator (I guess that's just another, more explicit way to ask the same question as above).
Thirdly, how do I determine what the GVW is for my truck so as to order the right wiring harness and actuator if replacement of the actuator is required?
Fourthly, I saw on the TSB
Lastly, if anyone has any thoughts about the braking induced pulsations I'd be interested in hearing them. While we had the truck on stands and when the braking had adequately heated the brakes to cause pulsation I believe I noticed a bit more runout in the brake disc than when it was cold. But I considered the test a bit of a failure as the passenger side hub would not spin in 4wd.
Many thanks, and, sorry for the long post. I just wanted to be as specific as possible about the symptoms of the problems.
LongFisher