i have a 1998 2wd blazer when i drive for more that 2 hours the transmission shifts really hard for the first shift when it is around 25mph, but then if i park the truck for like 20min then start it back up it shifts just fine,a friend of mine says its something called transmission module, but i've searched the part online and haven't found anything is there such a part or is there something else that could be wrong? any help would be great

 

When was teh last time you changed the fluid and replaced teh filter? Do u have any shift kits like teh B&M shift +?

 

how is the fluid level and condition. low fluid level could make it shift abnormally. check engine light on?