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Discussion Starter #1
The book says I can go into 4-wheel at any speed. Is there a max recommended speed? I ask because I'm getting a weird humming sound, almost a vibration, when in 4-wheel at speeds above 60 mph. is this normal or is this something I should have checked out? It's a 2001 2500HD. ????
 

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Oldman, some noise and vibration is normal above 60 mph. The front drivelines are just not that finely balanced. I've rarely run for much distance at that speed in 4wd. If the roads are clear enough to maintain 60+ I shift back to 2wd. That's the nice thing about any-speed shift-on-the-fly, if you get to a shady side of the hill or the conditions begin to degrade just stick 'er back in 4 high.
 

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I recall someone - maybe Maverick? - had noise and vibration in 4WD at highway speeds. I think it turned out to be a bearing. I had a 99 Ford that did this and it was a probelm with one of the auto engaging hubs. My '02 Dmax is noise/vibration free when engaged at any speed, but like Tom I don't routinely run in 4WD at high speed. Might be nothing in your case, but maybe worth getting checked.
 

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What you describe is a common complaint on these trucks. I believe that it is due to the slip yoke on the front driveshaft at the t-case. This seems to allow the front shaft to wobble a little at higher rpm under load. I put 100,000 miles on an '88 half ton Chevy, and tons of miles on older solid axle 4X4s, and all of those trucks ran without vibration at any speed in four wheel drive. Besides the slip yoke, the front driveline on these trucks is basically the same as what has been used since the '88 model year.Edited by: Black Dog
 

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Discussion Starter #5
Thanks folks. I've got 400,000 + on 84 and earlier Land Cruisers and older GMs, but am new to these IFS trucks. I routinely drive at 65+ in 4-wheel and have never experienced this with any other vehicle. I think it's headed in for a dealer check!
 

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would it be save to drive with 4 wheel engaged on dry pavement?


when it snows here, some road are cleared and some are still covered. I don't want to have to go in and out of 4 wheel drive all the time.


i know with my jeep i could drive in 4 wheel at all times.


thanks


vin


PS i have factory rear lockersEdited by: krash610
 

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I came off a dirt road pulling my trailer in 4x4 and forgot to put it back in 4x2. I noticed a new sound and a slight pull to the right when accelerating. Then I noticed it was still in 4x and took it out. The sound was'nt a bad sound really, just what you would expect of machinery working.


So it seems the truck doesnt particularly like dry pavement pulling a 9K trailer at 60mph but it didnt seem to hurt anything either. I switched out on the fly at 60 and it was butter smooth.
 

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If you use 4wd on dry pavement, you run the risk of tearing up the front end. I do not know exactly why, just that it is bad.
 

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on previous truck all 2500's i have accidently left in in 4-wheel





always got unusual noises and a really bad smell.....kinda like oil burning....


Craig
 

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Checking the four wheel drive on dry pavement is ok, it will not just tear everything up....BUT I would not recommend driving all over the place with it on. Turning the front wheels is what will give you the damage on dry pavement. If you want to check the 4X4 out make sure you have a long straight road....put it in four wheel drive and go. When you are done checking it take he out and you should be fine.


By no means is it a fulltime 4wheel drive.
 

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WillowCreekStable said:
I recall someone - maybe Maverick? - had noise and vibration in 4WD at highway speeds. I think it turned out to be a bearing. I had a 99 Ford that did this and it was a probelm with one of the auto engaging hubs. My '02 Dmax is noise/vibration free when engaged at any speed, but like Tom I don't routinely run in 4WD at high speed. Might be nothing in your case, but maybe worth getting checked.

I have the EXACT same problem on my 03, it's at the dealer right now. My noise is WAY bad with my 10,000lb 5er behind it and starts in at around 30 mph (with the trailer hooked up). I'd be very interested to know what bearing was bad.
 

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Discussion Starter #12
I took mine in Sat and was told the pinion nut was over torqued. The pinion bearing is going and it seems the resulting vibration is taking out the T-case output shaft bearing. At least, that's what I was told Sat. This morning I get a call from the dealership saying an inspector has to look at everything to determine whether or not they will replace the whole T-case. I'm thinking I didn't get the whole story on Sat!!
 

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I forgot mine once in 4wd on dry pavement and it took me 20 miles to figure out why things sounded and felt differently - did the same - shifted on the fly back to 2wd and everything back to normal. I think minor differences in tire wear from front to back may have something to do with it- that changes your effective differential ratios slightly and since they are locked together in 4wd things tend to run a little tight. My mechanic informs me this is why regular tire rotation is so important on these heavier powerful trucks. Edited by: army
 

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I tested the 4X4 out for the first time today and above 60mph there was a hum and vibration when I was giving her fuel....took the fuel away and it stoped. The truck was also a DOG in four wheel drive.
 

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Here is my .02 on leaving it in fourwheel drive on dry pavment.


This is very hard on the front end, driveshafts, transfere case right back to the transmission. has anyone jacked up a fourwheel drive pickup that was still engaged in fourwheel drive? I will tell you the tires will rotate about 1/4 of a turn before you even get them all the way off the ground ( this is known as drivline wind-up) and is trying to release the force that is applied to your driveline. U-joints and CV-joints are the first to go when this is done much, then the transfere case is next.


Also if you ever had tires that were a different size on a fourwheel drive you may not be able to get it engaged and if you do, you probably won't be able to get it disengaged with out jacking it up to relieve this stress on the driveline ( happened to a friend whos truck was stuck in fourwheel drive and had me check it out, found he had a flat tire and put a smaller tire on it. Kind of funny he said it was making some weird noises..)


I know the truck will handle driving on dry pavement in fourwheel drive to some degree, just beware that you are not helping the driveline system. Hope this gives you some more insight on the do's and dont's. Been driving GM fourwheel drives since 1980 AND HAVE DONE ALL WORK ON MY VEHCILES. See Sig Good Day, Fran
 

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Discussion Starter #16
I dropped it off at the dealer tonight. I got a bit different story this time. They have a list two pages long of every bearing in the front diff and the T-case they say they are going to replace. An inspector is going to take a look and decide whether or not to just give me a whole new T-case. I'm finding it hard to believe an over torqued pinion nut caused all this!!
 
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