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Discussion Starter #1
I've got a strange situation. Two days ago, I took my truck out for a drive. As I was leaving my driveway, I noticed that it felt like 4WD was engaged. I confirmed that it was definitely not engaged. Thought it might be the fan, but it was also not on. I drove about 60 miles that day and the condition did not change. Here's what I noticed:

1. Could hear a very slight hum when on the accelerator. This coincided with the rpms. The higher the rpm, the louder the hum.
2. Could feel a slight drag on the drivetrain. As if it were in 4WD, or something was engaged on the motor. About the same as when the fan is on, but without the tell-tale noise of the fan.
3. When rolling off the throttle, could feel a drag as I rolled to a stop. It is definitely not as free-rolling as it usually is. It also feels like it's downshifting as I roll to a stop.

The condition is significantly exaggerated in tow/haul mode. The hum is much louder and the drag heavier.

I'm beginning to think it's the transmission. It's as if the grade braking is continuously engaged. Anyone else hear of such a thing?
 

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Cold makes them feel strange.Where are you?
 

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Discussion Starter #4
I'm in Seattle. It's probably in the 40's today, so not very cold. We had some sub-20 degree weather a few weeks back and I didn't notice anything then.
 

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It's not the cold then!
 

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I have a thread running about the brakes engaging while turning the steering wheel. Sounds a lot like what was happening with mine, but you could bring truck to complete stop by turning the wheel sharply left or right. As long as it was rolling straight you couldn't really feel the drag but even a small correction with the wheel would cause it to feel like you were dragging something.
 

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Mine does the exact same thing! Even did it when it was 90 out, and it doesnt happen all the time. I've taken it into the dealer 3 times, and they can never reproduce it but I'll be damned if it doesnt happen the next day. :rolleyes:
 

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Discussion Starter #8
I'll try testing the brakes. I found several threads in the Allison OEM forum about transmission "whine". Could be the same thing I'm experiencing. But no one in that thread has mentioned any drag. I suppose it's possible that it's been like this from the start and I'm just now noticing it.

SubTexel, does your truck do the transmission thing? Or the brake thing? I'm reluctant to take it in to the dealer because I know I'll get the "we can't find anything wrong" response. In my case, I doubt anyone could feel anything is wrong because they don't drive the truck every week. I'm going to watch it for a few weeks and see if my gas mileage plummets.
 

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tmkhsv;1575747; said:
I'll try testing the brakes. I found several threads in the Allison OEM forum about transmission "whine". Could be the same thing I'm experiencing. But no one in that thread has mentioned any drag. I suppose it's possible that it's been like this from the start and I'm just now noticing it.

SubTexel, does your truck do the transmission thing? Or the brake thing? I'm reluctant to take it in to the dealer because I know I'll get the "we can't find anything wrong" response. In my case, I doubt anyone could feel anything is wrong because they don't drive the truck every week. I'm going to watch it for a few weeks and see if my gas mileage plummets.
Mine does the same as yours, not exactly sure what is causing it. I'll step on the gas and it's noticeably louder and seems to have power loss compared to normal, and engine braking is very prevalent... It'll go away after about a mile or so, and you can hear the noise drain out and the power all comes back. And it only happens when I step on the gas... I've also noticed oil pressure is higher than normal when this happens (normal meaning compared to other times at the same speeds and load when the noise does not happen)
 
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