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02-19-2013, 12:39 AM #1
Binding when turning in Auto 4wd and noises
The other day, I had my truck in auto 4wd mode. The roads were mostly snow covered but there were some areas that were just wet. I rolled up to a 4 way stop sign where the road was just wet. I made a right hand turn after stopping and the drive-line binded up so bad, it was almost enough to stop the truck mid-turn!. It felt more like it was in 4wd high rather than auto mode. Made wierd rubbing/groaning noises. It made noise on turns before but never actually binded like that.
I bought the truck with about 70k miles and it now has 104K. The drive-line has always been sorta "rough" and noisy but never binded up like that in auto. A couple years ago, I changed the diff and tcase fluids and replaced all the u-joints. Never noticed any excessive amount of metal "paste" on the drain plugs (none in the tcase). Truck "hums" even in 2wd when it's cold outside. Barely hear it in the summer. Auto makes more noise and 4wd high is very noisy in any temperature, especially when accelerating. I had thought the "hum", which seems like its coming from the front, was the wheel bearings, but I replaced both of those when the ABS sensors started acting up, and the sound was unchanged.
I'm trying to narrow this down. I think the problem is all in the tcase BUT the humming sound at speed sounds like it's coming from the front. However, I know sounds/vibrations can sorta transmit along one part of the drive-line to another. One thing I do know is coming from the tcase is a ton of play/slop when shifting into reverse. When i put it in 4wd and shift to reverse, the slop is gone.
Any tips on narrowing this down is appreciated.
02-19-2013, 05:08 PM #2
When you select Auto4x4, the t-case clutches start to engage and a small amount of torque is sent forward (maybe 5%). When rear wheel slippage is detected, the clutches fully engage, splitting the torque font and rear.
Sounds like you have more than "stand by" clutch engagement. One of the internal bearings has been know to fail, perhaps that is your problem.
If the noise is coming from the front, perhaps a bad bearing in the front diff.Ray
'09 Avalanche LTZ - Black
'05 Envoy XL (sold)
02-19-2013, 11:34 PM #3
Interesting. The noise in 2wd from the front (or seemingly from the front) is mostly noticeable at around 50 mph+. If I'm cruising along at a steady 50-55 mph and hit the auto button, the noise goes away.
02-20-2013, 12:17 AM #4
does the sound come from the drivers side?
1995 Silverado 4x4 (Sold)
6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge
2005 Yukon XL Jet Power Programmer, EGR Window Visors, EGR Hood Shield, Denali Headlights, HIR1 9011 Bulbs, White Night Rear lighting system http://www.gmtruckclub.com/forum/sho...5-GMC-Yukon-XL
2002 Silverado ext cab 2wd (Sold)
2003 Yukon XL (Totaled)
02-20-2013, 12:25 AM #5
02-20-2013, 08:01 AM #6
I would take it to a ring and pinion shop.Most will check it out for free. I had a bad driverside bearing in my front diff. it made the same noise.
02-20-2013, 01:03 PM #7I made a right hand turn after stopping and the drive-line binded up so bad, it was almost enough to stop the truck mid-turn!. It felt more like it was in 4wd high rather than auto mode.
I don't know if it stayed the same, but the fill plug on my tcase is a square 5/16" drive plug. I ended up buying a 3/8 socket adapter and grinding it down to 5/16 so it would fit.'98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
'92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
"My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World
02-21-2013, 10:12 AM #8
02-21-2013, 11:52 AM #9
i thought auto 4x4 worked by leaving the front diff engauged (right axle shaft locked together) and then the trasfcase was 4x4/4x2 engaged as nessary? i belive if your front diff is engauged rather its 4x4 or 4x2 you will get the binding action."i dont think you got the picture. i got a beautiful picture. this baby happens to have an extra turn of speed, which is the only thing i care about. you dont understnad what happens do you? they make cars. they make 'em exactly the same way. one or two of 'em turn out to be something special. nobody knows why. i know why. i may be kiddin' myself, but i think i can make somethin' out of that sad little bucket of bolts." ~ Tennessee Steinmetz
02-21-2013, 07:50 PM #10
The trucks that only have AWD, do not have the passenger axle disconnect, both axles are connected to the front diff at all times.
Although the front diff is an open diff, both axles connected to the diff will cause the front driveshaft to turn. As the front wheels turn in two different radius, which is also different than the rear turning radius, the front and rear driveshafts will turn at different rpms; therefore, internal t-case slippage is necessary to prevent binding.
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