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Discussion Starter #1
Hi, i just bought my first truck 14 days ago. It's a 04 1/2 Gmc 2500 HD Duramax with automatic transmission (allison).

When i'm on tow haul (with trailer or no trailer), after shifting in 2 nd gear, there is a funny noise that last for 1 or 2 seconds. It only does that on tow haul ???

The sounds is like BOOUVVVVVVVVVVVVVVVV.

Can any body help me ?

Is it a major transmission problem ?

The truck as about 40 000 miles.

Phil
 

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That might be your torque converter locking and you hearing the allison whine. (tow haul will lock the torque converter in 2nd gear on up and raise the shift points) When is the last time the tranny was serviced? I don't know if you got any record of it. Also, it might be time to change the external filter on the tranny. There should be a magnet on top of the filter that you have to swap over.
 

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Discussion Starter #3
I dont kwow when the last time the transmission was serviced, a got the truck like 14 days ago from a dealer .
Do you think that a transmission oil and filter change could solve the problem.

The owner before me tow a fifth wheel for is vacation.
 

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Discussion Starter #4
Ive notice too that the sounds get louder as the transmission gets hotter , and or when the wheater is really hot !


Phil
 

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How does the tranny fluid look and smell? Check the level too once you get it up to operating temp. The allison has a "whine" to it that you can hear when going slow....some trucks are louder than others. How does it shift otherwise?
 

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Discussion Starter #6
i didnt check that yet, what is the tranny oil suppose to smell and look like ?
Other wise, it shifts really smooth.
Do you think that a oil and filter change could solve the 2 seconds noise in 2nd gear on tow haul ?
 

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it should still be red, maybe dark red and not smell burnt. Personally, I would change the fluid and the external filter since you don't know when it was done last. I don't know if it will fix your problem. It might be normal, I guess I haven't really noticed it on mine since my exhaust covers most the other noises.
 

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Yeah change the spin on and change the ATF just to be safe. If it still does it after that we'll have to think of something else.
 

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Discussion Starter #9
Today, iv'e changed the oil and the filter of the transmission, and for now, no more noise.
The oil was dark red and smelled burn, and there was a lot of "/$%?&* on the magnet over the filter.
7 liters of new oil and a filter seems to have solve the problem, for now ...

Thanks a lot !

Phil

2004 2500 HD Duramax LLY.
 

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Is there an allison dealer close to you? I would talk to them and see if it is normal. I am willing to bet that what you are hearing is the allison whine or the torque converter lock up. If there isn't an allison dealer close by I would take it back to the dealer and have them look at it. It sucks trying to diagnose a problem over the internet.
 
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