I'm pretty sure theres an aftermarket kickdown valve in the tranny that can be replaced. However I'm not positive. Basically when im thundering down the highway, the car seems to have more to give but can't. The thing is the pedal is only half way down, if I push it a little farther it kicks down way to early. It's like I can't get full use of the tall gear. Anyone know if there is a part that can fix this?

 

yea.. Summit carries the part ou are looking for. ussually the tranny will kick out of gear and into the one lower at around 60% throttle.. give or take.. the TV Boost valve i think it is stops that and aises it to 80% i think.

Or you can go this route

also from summit.

BMM-70249

$119.88
Brand: B&M
Product Line: B&M TH-700R4 Wide-Open Throttle 3-4 Upshift Kits
Quantity: Sold individually.

Automatic Transmission Controller, Buick/Chevy/GMC/Oldsmobile/Pontiac, TH700R4, Each

* Check to make sure this part fits your application

Get wide-open throttle!
These upshift kits from B&M are designed to provide wide-open throttle 3 to 4 upshifts for TH-700R4 (4L60) transmissions. Most TH-700R4 transmissions will downshift from fourth to third gear at about 3/4 throttle. This allows the transmission to remain in fourth gear at full throttle.

 

You can remove the TV plunger sleeve (without removing the valve body) and install 2 small allen screws in the part throttle 4-3 downshift passages, then grind with a Dremel to clear the TV plunger valve and valve body. The allen screws cost about .40 cents for the two. Find the schematic for this, and you will see what needs to be done.