Attention: TDR Forum Junkies 
Definately not Engine related, and so far I can't confirm if it's trans related.....
I'm not sure what I have..... Empty, the truck drives just fine around town. But when I hooked up brothers empty 3-place snowmobile trailer (~2500-3000 Lb) and hit the road we got this horrendous grinding noise at 60-65MPH and above. It only seems to occur while under acceleration, or sustained speed on an uphill grade (no noise while decelerating or coasting downhill ) and it really gets bad on the steeper hills. It also seems that it only occurs when the trans in in 4th and TC locked up. It improved significantly if I switched from Tow/Haul to OD-Off mode (but did not completely go away). I didn't do much driving with the trailer on in other than Tow/Haul or OD-Off. Initially, it seemed like the noise (grinding sound and vibration through the floor) was coming from the rear axle area. We stopped and my brother got in the back of the truck and said the noise in the bed/canopy area was really noticeable back there, and thought it was centralized right over the axle area. He said it seemed directly above the axle and same intensity from wheel well to wheel well. After we dropped off the trailer, I took it in to the dealer in Boise; they test drove it (without the trailer) and didn't hear anything. They said they visually checked the rear axle and the drive line and it checked out OK. Diff fluid level was good, and they put a magnet down in the pumpkin and it came out clean.
It ran just fine during a 250 mile side trip in So. Idaho (not towing) and shift are normal and firm as to be expected.
The grindgin and vibraion got worse on the way back home north bound US 95 Boise to Lewiston; to the point I wasn't sure we'd make it up the Lewiston grade. 50MPH max on the hill. If I engaged 4-wheel drive things either quieted down or were masked by the front end helping with the pulling. Once I dropped off the trailer back in Spokane things quieted down a lot, so I went ahead and drove on home Friday night. As long as I kept speed below 60 it was pretty quiet; and I got great mileage (22. 9). But now even without the trailer at speed above 60-65 or while climbing the grinding sound and vibration through the floor comes back. And now the noise seems to be coming fr o m a more forward location than originally noted. I feel it through the driver side floor and it seems to be somehow related to the 4WD being engaged or not. Quieter when engaged than when not engaged.
I did another visual inspection of all driveline components on Saturday. I checked the level, then drained and refilled the transfer case . The fluid cean and clear with no particle residue visible. I drained the transmission and pulled the pan to see if there was debris. Nothing. Fluid has browned quite a bit and the smell was different that new ATF+4, but otherwise clean, very little clutch residue in the pan. I filtered the fluid trough a tee -shirt and put back in trans.
I also pulled the front driveshaft . The U-joints felt great and slip yoke was nice and smooth; I lubed the CV joint and slip yoke while I had it out.
I'm mystified and very reluctant to drive any distance or over any of the local passes till I get it sorted out. For now I just sit around trying to imagine what it could be. I think I'll go ahead and drain, inspect and refill the rear axle this weekend. And maybe do a bearing swap while I'm at it just to be sure.
Truck is in sig below. I have been running Smarty at Level 3 for about three years (30-40K mi). I only tow light; less than 6000 lb, and infrequently. I do experience the well documented stutter-shift (1-2-1) under light throttle, and it seems like it has been slightly more frequent lately. Other than that, and the condition noted above, the truck has been flawless.
I have not seen this symptom documented anywhere else on the site, so I must be the first to experience this mystery. Anyone have an idea where to look next??
I'm not sure what I have..... Empty, the truck drives just fine around town. But when I hooked up brothers empty 3-place snowmobile trailer (~2500-3000 Lb) and hit the road we got this horrendous grinding noise at 60-65MPH and above. It only seems to occur while under acceleration, or sustained speed on an uphill grade (no noise while decelerating or coasting downhill ) and it really gets bad on the steeper hills. It also seems that it only occurs when the trans in in 4th and TC locked up. It improved significantly if I switched from Tow/Haul to OD-Off mode (but did not completely go away). I didn't do much driving with the trailer on in other than Tow/Haul or OD-Off. Initially, it seemed like the noise (grinding sound and vibration through the floor) was coming from the rear axle area. We stopped and my brother got in the back of the truck and said the noise in the bed/canopy area was really noticeable back there, and thought it was centralized right over the axle area. He said it seemed directly above the axle and same intensity from wheel well to wheel well. After we dropped off the trailer, I took it in to the dealer in Boise; they test drove it (without the trailer) and didn't hear anything. They said they visually checked the rear axle and the drive line and it checked out OK. Diff fluid level was good, and they put a magnet down in the pumpkin and it came out clean.
It ran just fine during a 250 mile side trip in So. Idaho (not towing) and shift are normal and firm as to be expected.
The grindgin and vibraion got worse on the way back home north bound US 95 Boise to Lewiston; to the point I wasn't sure we'd make it up the Lewiston grade. 50MPH max on the hill. If I engaged 4-wheel drive things either quieted down or were masked by the front end helping with the pulling. Once I dropped off the trailer back in Spokane things quieted down a lot, so I went ahead and drove on home Friday night. As long as I kept speed below 60 it was pretty quiet; and I got great mileage (22. 9). But now even without the trailer at speed above 60-65 or while climbing the grinding sound and vibration through the floor comes back. And now the noise seems to be coming fr o m a more forward location than originally noted. I feel it through the driver side floor and it seems to be somehow related to the 4WD being engaged or not. Quieter when engaged than when not engaged.
I did another visual inspection of all driveline components on Saturday. I checked the level, then drained and refilled the transfer case . The fluid cean and clear with no particle residue visible. I drained the transmission and pulled the pan to see if there was debris. Nothing. Fluid has browned quite a bit and the smell was different that new ATF+4, but otherwise clean, very little clutch residue in the pan. I filtered the fluid trough a tee -shirt and put back in trans.
I also pulled the front driveshaft . The U-joints felt great and slip yoke was nice and smooth; I lubed the CV joint and slip yoke while I had it out.
I'm mystified and very reluctant to drive any distance or over any of the local passes till I get it sorted out. For now I just sit around trying to imagine what it could be. I think I'll go ahead and drain, inspect and refill the rear axle this weekend. And maybe do a bearing swap while I'm at it just to be sure.
Truck is in sig below. I have been running Smarty at Level 3 for about three years (30-40K mi). I only tow light; less than 6000 lb, and infrequently. I do experience the well documented stutter-shift (1-2-1) under light throttle, and it seems like it has been slightly more frequent lately. Other than that, and the condition noted above, the truck has been flawless.
I have not seen this symptom documented anywhere else on the site, so I must be the first to experience this mystery. Anyone have an idea where to look next??
