Alaxgoaly8
TYF Newbie
- Joined
- Feb 11, 2023
- Posts
- 11
- Reaction score
- 1
Alright... Had a Trans rebuilt to 4L75 spec with an enhanced torque converter in Dec 2024... 2004 Yukon Denali 6.0 AWD, 185K miles. Not sure if the trans rebuild has anything to do with what's going on...
Since then, it shifts smooth and don't have complaints except...
On the highway at 70ish mph, let off the accelerator to coast and I hear a noise like a bass drum under the car (duh, duh, duh, duh). Step on the accelerator and it quiets down (but doesnt totally disappear).... Same thing will happen at 60/70mph and going uphill with foot on the accelerator. Same droning noise. No vibrations in the steering wheel at all. Can feel slight pulsing through the gas pedal when it happens but it's barely noticeable. The noise gets louder as the car is up to temp the longer it runs VS just starting out and cool. Nothing overheating from the gauges or by looking at it. The noise gets louder the longer you're on the highway (but just when coasting around 70mph or light accel going uphill). Go down around 55, noise goes almost completely away.
I also don't know if it did this before the trans rebuild because I wasn't taking it on the highway before it was done cause of the slipping.
Had both front wheel hubs and brakes and rotors done on all 4 corners. New front axle on the driver's side (boot was torn).
Changed the front and rear diff fluid and didn't see metal in either. Fluid looked decent...
Took it to the mechanic that did the trans rebuild to see what they say, but they can't pinpoint the issue and they didn't want to throw parts at it. They think the issue is in the rear somewhere. They had it on the lift and didn't see issues with the u-joints. They said to see if it gets worse so it's easier to diagnose.
Anyone have any ideas? Unbalanced drive shaft (although figured I'd have some decent vibration if it was that)? Thought about maybe the wheels and tires (original Denali 17's with 3 year old Michelin's on it with good tread), but again, thought I'd feel more vibrations somewhere? Maybe a rear tire is unbalanced or a bent rim? Loose u-joint maybe just not tightened to spec when putting the trans back in?
Shifting is smooth, engine is smooth, no other noises. And no big vibrations at highway speeds. It rides great otherwise.
I'm baffled by this one. Figured I'd ask here before taking it into another shop. Thanks for any recommendations.
Since then, it shifts smooth and don't have complaints except...
On the highway at 70ish mph, let off the accelerator to coast and I hear a noise like a bass drum under the car (duh, duh, duh, duh). Step on the accelerator and it quiets down (but doesnt totally disappear).... Same thing will happen at 60/70mph and going uphill with foot on the accelerator. Same droning noise. No vibrations in the steering wheel at all. Can feel slight pulsing through the gas pedal when it happens but it's barely noticeable. The noise gets louder as the car is up to temp the longer it runs VS just starting out and cool. Nothing overheating from the gauges or by looking at it. The noise gets louder the longer you're on the highway (but just when coasting around 70mph or light accel going uphill). Go down around 55, noise goes almost completely away.
I also don't know if it did this before the trans rebuild because I wasn't taking it on the highway before it was done cause of the slipping.
Had both front wheel hubs and brakes and rotors done on all 4 corners. New front axle on the driver's side (boot was torn).
Changed the front and rear diff fluid and didn't see metal in either. Fluid looked decent...
Took it to the mechanic that did the trans rebuild to see what they say, but they can't pinpoint the issue and they didn't want to throw parts at it. They think the issue is in the rear somewhere. They had it on the lift and didn't see issues with the u-joints. They said to see if it gets worse so it's easier to diagnose.
Anyone have any ideas? Unbalanced drive shaft (although figured I'd have some decent vibration if it was that)? Thought about maybe the wheels and tires (original Denali 17's with 3 year old Michelin's on it with good tread), but again, thought I'd feel more vibrations somewhere? Maybe a rear tire is unbalanced or a bent rim? Loose u-joint maybe just not tightened to spec when putting the trans back in?
Shifting is smooth, engine is smooth, no other noises. And no big vibrations at highway speeds. It rides great otherwise.
I'm baffled by this one. Figured I'd ask here before taking it into another shop. Thanks for any recommendations.
