Quote Originally Posted by Fivefingerdeathpunch View Post

The 4T65e HD is the only transmission that was put in the supercharged and V8 GXP cars. The 4T65e which is exactly same minus the gear ratio and HD diff are in the regular SE, GT, Base model cars. The HD transmission is not any stronger than the regular transmission but to be a direct drop in replacement you need a 2004-2007 GTP/GT(supercharged 06-07) unit to work, if you went that route. Also the COMP G transmission run a different gear ratio as well compared to the standard GTP cars, another small change GM did.
Thanks for the link to the site. That might help when I get the codes out.

Your comment on the HD transmission needing to be used in the GTP is also helpful. Just checking what I might do, I went to two auto parts places to price a remanufactured trans. At least one of them had both an HD and non-HD transmission shown as appropriate for my GTP. What a disaster it would be to pay to have the wrong one installed.

Terry