The Express I have has a noisy mechanical rattle from the mid part of the transmission, forward of the pan. It rattles on tickover when in Park or Neutral. In gear and when the truck moves, the noise goes away. Photo below, anyone any ideas what this rattle could be? Also, where would I find the info that would give me the model number/type? It's a 4 speed auto

 

Going back to the VIN Decoder, go to the Tech Specs, scroll down to the Transmission Order Code, it will probably be M30, which is a 4L60E. I highly recommend you getting a commercial VIN Decoder from compnine.com. It costs $5 for a complete build sheet with original build information for that VIN, 2 or 3 pages, and can decode five vehicles for that $5.

 

Thanks for the build spec advice Twscarp I shall give them a shot to get the spec. When I highlight over my VIN spec on GMPartsGiant.com, it comes up with 4-speed autmatic transmission, THM-R2(4L80-E) I'm guessing this might be a variant of the model you suggested?
No ideas on the rattle from the cetral part of the 'box though?

 

The only parts forward of the pan are the torque converter and flywheel. My bell housing has two inspection ports, which are good places to shine a light and see what's going on. Failing that, you're probably looking at dropping the tranny.

 

Thanks Joe, I will serch out the inspection hatches

 

I would start with a tranny service, inspection and road test at a good tranny shop.

 

Does look like the transmission has a break and something going on at the top of your picture you posted
Thank you
Ken