JapanAaron

Yes, it's another one of those "service 4wd" questions.. sorry. Stationed in Japan in the US Military, just purchased a 99 Silverado stepside, 37xxx miles and electronic push button selector w/Autotrack 4x4. After driving the truck for approximately 2 hours continuously, the "service 4wd" is indicated in the service window. All the lights on 4wd selector are illuminated as they should be with only the 2hi illuminated. After I turn the truck off and restart it, the "service 4wd" is gone, but comes back within a few minutes. Also, how noisy is the 4wd supposed to be? I have been around 4x4 Chevy's since I was a kid and never had them as noisy as this one.When the 4x4 is engage it also doesn't like to make turns without making aLOT of noise and somewhat jerky. Had the truck up on a lift today and all the u-joints look fine. If Japanese Chevrolet dealers didn't charge such crazy prices, I would take it to Chevrolet and letthemrun the diagnostics to pull the code. Anysuggestions are greatly appreciated. Ifind it hard to believe that there could be anything seriously wrong with the truck since it has such low mileage and was used as a show/advertisement vehicle for aJapanesespeed shop.

ukrkoz

bud, you ARE NOT SUPPOSED TO DRIVE IN 4WD! only under strenuos road conditions! read manual.
yes, it is noisy!!! GMC has a six page letter of clarification issued on it saying "that is normal". and tells us to kiss their corporate ***.
u-joints are binding/trnasfer case is binding when turning in 4wd, thus the scary sounds. once again - don't drive in it unless you have to.
which 4wd are you referring to? 4awd/4hi/4low? lord save you from driving in 4low!
those switches are notorious pos, but assuming that light goes off after you disengage/turn off, i'd say your transfer case does not like it.

JapanAaron

Don't worry, I'm not driving around in 4wd,I do know better than that.I was just doing an initial test to make sure that it operated correctly. It was a short testand was only engage for approximately 200ft before I disengaged it. I was in4hi whenitwas making the soundsin question. Theswitch seems to be operating fine. All the selectables seem to work fine and theselector lightworks as it's supposed to. Any other sensors or actuators that could be causing the "service 4wd" code? Thanks for your input ukrkoz

ukrkoz

ok, then i have a simple one for you, as i have just been through this:
make sure your front and rear tires are SAME SIZE and ARE WORN OUT EVENLY. (stick a coin or gauge between the treads) that transfer case is VERY sensitive to differnt diameter tires. VERY!!.
otherwise, who knows. it's GMC product, anything's possible. when was the last fluid change in transfer case/front differential? supposed to be done religiously!

JapanAaron

ukrkoz, I just changed the tires two days ago with brand new ones. The old ones were dry rotted and had a flat spot from sitting for so long, but still get the "service 4wd" indicator. I doubt that the transfer case or front differential fluidshave ever been changed. Does the front differential use the standard 75w-90 gear oil? I have a Chiltons and Haynes manual on order and hopefully will have them shortly. What fluid recommended for the transfer case? Thanks again for your recommendation.

ukrkoz

also, what exactly do you mean by this? i am lost. either ALL lights illuminated, or ONLY 2hi? if all lights, switch is not right. it should blink between the mode changes, like 2-3 blinks for both modes and then solid one for the current mode.
i think fluid should be changed at 30K. mine was at 60K(done by me, previous owner changed squat), switch dies on me at 58K.

ukrkoz

well, no easy cure for you, bud. i DO NOT dare to use anything else but GMC fluid on this. they have their propriatory fluid. i am totally synthetics fan, but for this one and for my wife's lexus, i use their brand fluids. GMC's is sort of blueish/greenish one.
ok, i have it in front of me: AUTOTRACK 11 TRANSFER CASE FLUID, 1#12378508 GR.8.800 says not to drink it, makes you too high.
as of front diff, not sure, ask dealership. probably some propriatory stuff too, i don't remember on mine.
funny thought. i had, 2 mths ago, brand new tires installed on the rear end. they ordered right size, but received wrong one, did not check, and it locked my differential after about 50 feet drive. pissed i was!![][][]

ukrkoz

you know if that truck was sitting for so long that tires went dry rotten - fluids probabaly did same. oils go sour, you know. it's not the mielage, it's TIME. oxydization, mother of all evils.

you got me going on this one, didn't you? SAE 80W-90 front axle. i am assuming they are referring to front diff, as in their manual wisdom they can't use human language. transfer case stays - their lube only.

JapanAaron

ukrkoz, thanks again for your assistance. What I meant by the lights on the 4wd selector is that the selected driveline choice is the only lamp lit.... so it's operating correctly. Tires are correct, I just double checked and they are all the same size. Will look into changing the front axle/differential oil sometime soon. I doubt that I will be able to change the transfer case oil over here since the oil will be almost impossible to acquire. Chevrolet dealerships over here won't even acknowledge your existence unless you purchased the vehicle from them new. Will probably have to stick it out and wait until I return to the US in 21 months. As for the dry rotted tires, the tires were installed 6 years ago.. so they were due for change. Everything else on the truck (belts, hoses, plug wires, etc.) look like new. Thanks again

JapanAaron

ukrkoz, according to your manual, how many quarts of the Autotrack transfer case fluid is required to fill the transfer case? Thanks again