Allison ? on noise

[gillguy]

I just noticed a noise on my truck yesterday when I went from D to P. I was unhooking a trailer so I had the door open an when I pulled forward a little then put it in P it sounded like the bottom was falling out. I then tried it again and nothing, nice and quite. So I shifted thru the gears again while setting there, went P to D then P again and it would duplicate the noise, sometimes louder than others. I then called the dealer and went over there this morning and now have an appointment in Albany GA at an Allison shop.
Anyone heard of this or have any ideas? I have 6300 miles on it. I put 2167 miles on it before I towed my TT with it, though I did pull a light trailer with it before then. I now have over 3K miles towing my TT with it but I don't think that should hurt it, my TT is a Rockwood 8317SS and only weighs about 7500 loaded.
Thanks
Bobby

[Duramaster]

Sounds to me like it is the park pawl in the transmission. This has been an "on again/ off again" complaint with customers. Especially ones that are not familiar with trucks. The park pawl in the Allison transmission is HUGE and the noise can not be duplicated everytime. BUT for piece of mind, If you already have the appointment with the Allison shop then you might as well go and have it checked out. ;)

[gillguy]

Going from a manual tranny to a auto like the Allison, I just thought it would be quite, like the auto tranny in my wifes car.
One of the techs at the Chevy place said he's heard it before, but he said the same, go on over and let the Allison boys check it out.
I'm thinking on hitting the dealer up on a tank of fuel too since I have to drive over an hour away for something they can't do.
Let you know on Monday what they say about the noise.

[gillguy]

Ok. Returned from my trip to the Allison shop. My tranny checked good.
They said the noise sounds more like it's in the drive shaft or to much free play in the rear end. They do not know the acceptable limits of free play in it, but it does look like when you go from P to D it do rotate pretty far without turning, even from R to P it rotates some then when you go back to P it returns to like a nuetral postion but makes the loud clunk noise.
I'm going to take it to another Chevy dealer next to see what they say.

[moss6]

If you are new to the allison I am not surprised that you are alarmed at the noise they make when parking; especially in the garage here the noise is amplified because of the confined space. Really sounds like some damage has to be occuring with the dreadful clunk eh! Not to be alarmed though, this is quite normal and in no way detrimental to the transmission; remember this is a HD tramsmission unlike any other on the market that is used on a otherwise light to medium duty truck. Try to just view the noise as a verification that your transmission is far and beyond the marginal units that Ford and Dodge are forced to accept.

[DieselMonk]

I've got that noise too, not that lound, but it is there.