2000 Blazer surging while driving

ninthplain

Hello all,
When I am driving and get around 45 miles per hour the tach begins to bounce and the car feels like it is surging. Step on the gas and it quits, eventually around 65 - 70 it appears to stop. I have had the fuel pump tested and the filter has been replaced with no improvement.
It almost feels like Overdrive is not working.
Any thoughts?
Ninthplain

wuddarush

Mine is doing the same thing. I have a 1998 v6 4wd blazer. When im driving it starts to surge and the tach jumps. It also seems to shut off the cruise control while in cruise mode. Sometimes the cruise wont work again until it surges again. Could it be a vacuum leak somewhere? I have had the FP replaced a year ago. It has never had a tune up. If you figure anything out, please post as i will do the same.