U-Joint Question

Lance Link · August 5, 2003

Has anyone had to replace the u-joints in their front driveshaft (4 wheel drive trucks)? My '99 has been making a grinding noise that I can feel in the floorboards and through the steering wheel, as well as being audible, for a few months. Both front hubs were replaced 10,000 miles ago and I just replaced both u-joints in the read driveshaft. Still have the problem. The front diff is clean and has recently been serviced. I have 95,000 miles on the truck.

Am I wrong to assume the front driveshaft rotates even in 2WD mode? I have the push button 4WD option.

MoJo · August 5, 2003

Front driveshaft does not rotate in 2WD mode with electric 4X4. Hubs and transfer case are disconnected.

U-joints do not usually 'grind' or made other, inside the cab with the windows rolled up, audible sounds. They will 'click', then 'clank' as they wear out.

Jack the truck up and place jack stands so that they support the axles, not the frame (Suspension loaded). Put the truck in gear and find out where the noise is coming from.

Be exceedingly careful, you don't want to be under the truck if it falls!

Jersey Tahoe LT · August 5, 2003

The front drive shaft DOES rotate while you drive. I have a 99 Tahoe that has the Autotrac system (4 buttons). I had the front U-Joint go on me and I had the audible clicking clacking grinding and rumble in the floorboard. It is most definatly the U-joint (s). Just get under the truck and try to shake the front shaft as you spin in. It will be lose and wobble. I had the dealership do it because the transfer case seal wore out due to the U-Joint rattling around under there. And I really didn't want to mess with that stuff. If you did the rears it is the same except on the front. Good luck. And let us know how you make out. Oh and if you are unsure if the axel spins in 2wd mode. Turn the axel and put a mark on it or find the sticker. Once you see it remember it's position. Drive around and then look under there again. You will notice that is is no longer in the same position.

Later,

Brandon

MoJo · August 5, 2003

The front drive shaft DOES rotate while you drive. I have a 99 Tahoe that has the Autotrac system (4 buttons). I had the front U-Joint go on me and I had the audible clicking clacking grinding and rumble in the floorboard. It is most definatly the U-joint (s). Just get under the truck and try to shake the front shaft as you spin in. It will be lose and wobble. I had the dealership do it because the transfer case seal wore out due to the U-Joint rattling around under there. And I really didn't want to mess with that stuff. If you did the rears it is the same except on the front. Good luck. And let us know how you make out. Oh and if you are unsure if the axel spins in 2wd mode. Turn the axel and put a mark on it or find the sticker. Once you see it remember it's position. Drive around and then look under there again. You will notice that is is no longer in the same position.

Later,

Brandon

Key words: Autotrack system.

I dont know what they call the 2 button system. Mine has a "2X" button and a rocker button marked "4X HI" and "4X LO".

There is an electric cable plugged into the front differential and when it's in "2X", the front drive shaft does not rotate!

silverado man · August 5, 2003

The front drive shaft DOES rotate while you drive. I have a 99 Tahoe that has the Autotrac system (4 buttons). I had the front U-Joint go on me and I had the audible clicking clacking grinding and rumble in the floorboard. It is most definatly the U-joint (s). Just get under the truck and try to shake the front shaft as you spin in. It will be lose and wobble. I had the dealership do it because the transfer case seal wore out due to the U-Joint rattling around under there. And I really didn't want to mess with that stuff. If you did the rears it is the same except on the front. Good luck. And let us know how you make out. Oh and if you are unsure if the axel spins in 2wd mode. Turn the axel and put a mark on it or find the sticker. Once you see it remember it's position. Drive around and then look under there again. You will notice that is is no longer in the same position.

Later,

Brandon

Key words: Autotrack system.

I dont know what they call the 2 button system. Mine has a "2X" button and a rocker button marked "4X HI" and "4X LO".

There is an electric cable plugged into the front differential and when it's in "2X", the front drive shaft does not rotate!

But if he has the NBS 99 than he would have the autotrack. And I'm pretty sure that the front shaft does turn but not 100% possitive.

Jersey Tahoe LT · August 5, 2003

Hey MoJo. I am not trying to say you are wrong. Calm down there buddy. I am only giving my experience. So it shows you that it could spin.

Later,

Brandon

Lance Link · August 5, 2003

I'll try marking the shaft and check after driving and will get back to you tonight.

Lance Link · August 5, 2003

For what it's worth, I called my dealer and they said the front shaft will spin but not at road speed. There's some degree of intertia that will cause the shaft to spin somewhat. I hope that's the case with my truck.

MoJo · August 5, 2003

For what it's worth, I called my dealer and they said the front shaft will spin but not at road speed. There's some degree of intertia that will cause the shaft to spin somewhat. I hope that's the case with my truck.

So, I'm still at a loss to diagnose the grinding noise. And, no, Jersey Tahoe LT, I didn't take what you said as a slam. Just saying, I don't know what Lance Link has and offering my experience.

There is a ton or differences from '98 to '99 so I'm operating in unfamiliar territory.

Thanks!

Jersey Tahoe LT · August 5, 2003

Aight. I know what you are saying. I still think it is his U-joints but you are right about the difference between the years. I have the 99Tahoe Old style so could be different but if the U-Joint is as bad as mine was it will bounce around as it spins. Good luck Lance.

Later,

Brandon

frdfandc · August 6, 2003

You best bet would be to take it someplace, either a drivetrain shop or the dealer. No offense, but its hard to diagnose a problem over the computer.

Lance Link · August 7, 2003

The shop can't find anything wrong. The hubs are tight, the front u-joints are fine, the front differential is fine, everything seems fine. 'Tis a mystery.