hey i just bought an 1985 full size chevy k5 blazer. the truck is the shizzz! but i took it out feild surfing ( tilling or tearing up the yard a bit) and well ever since then it has been acting strange. gets itself through first and second when moderately accelerating but then it seems to try to shift to third and goes to no where.. i later noticed that if i hound the throttle a little bit harder that after it pretty much shifts to nothing i will go to over drive or back to second, and then when i feel it getting high on the rpms i lef off but not completely and then it wants to shift to what i'm guessing is fourth because i'll be then doing about 55-65 mph. i had a leak in the trans but i fixed that the other night. just some dry rotting lines. so now it's all sealed up and i refilled what i lost in the tube swap. i also just changed the oil and filter. doubt that has anything to do with it though. oh and just a Q on the side my alternater belt squeaks real loud. new belt fix that? it's tight but not too tight. no slipping. just loud noise at start up. thanks for whatever you guys can do to help.

 

First off when dealing with transmissions, things that you might not think affect performance do. Fluid level, Fluid condition, Filter condition, shift points, shift firmness and the time it takes to shift into the next gear. Transmissions are touchy so pretty much everything that occurs during operation.

Check everything I just mentioned and when it shifts, if it is infact a hard shift that does not mean it is bad.

As for you belt issue, you can test the belt tightness by turning the belt 90 degrees after you have tightened the alternator down so it can not pivot and loosen. It should be pretty firm once it has rotated the 1/4 turn or 90 degrees. If the belt makes noise at start up only, its starting to wear out.