I'm having some issue's with my Allison trans in an 04' GMC 2500HD, 6.6l turbo. First off sometimes when I come to a complete stop there will be a bumping feel, and again as soon as I let off the break to go again. I read some stuff that makes me believe it could be in the drive shaft. However, I recently noticed trans fluid around the rear "controls" or where the electrical plugs are located. I took it in, and they told me its in the beginning stages of going out. The guy at the shop told me he got five codes, but I've yet to get a single warning light. They removed the pan, and it appeared to be dirt in it. To me it looked like dirty trans oil, they said it is "clutch material". I became skeptical of the alleged claim that they had five codes from the trans, because I have not had the first check engine light. It used to run in the 140-160 temp range, but now it gets up to around 200 without working it very hard. I had them change both filters, refill it, and I got it back. I was still able to get it up to 190 temp, in the 200 range it doesn't seem to shift quite as smooth as it does in the 140-160 range. I know there is probably something up with it, but these guys wanted to charge $3500-$4500 for a rebuild. I know something might not be quite right, but it doesn't feel like a $3500+ repair.
