We have a 2001 Blazer 4WD automatic transmission. It has 164,000 miles on it. While driving it will do a little "bump". It does it at any speed and not while it acclerates. My husband thinks it is a modulator? Does anyone have any suggestions? Does anyone have a transmission schematic we could have to look at? This is a good engine and has been a very reliable auto.

 

I had a similar problem. Sort of bucked. Changing the cap and rotor on the distributor helped. It ran fine and only did it at highway speeds.

 

Hey, thanks for the info. Will have my "back yard mechanics" check into it.