2004 Chevy Silverado knocks shifting 3 to 4 Gear in Drive
 

Dear members,

I have a 2004 Chevy Silverado 1500 4WD with 4 speed automatic transmission. When driving between 45-55 mph the truck tries to shift into 4th gear as it should however there is a constant knocking sound coming from the engine during this shift. However when the transmission shift lever is in 3rd this shift problem does not happen. I need to know what are some things that I can check and test on my owe before I have to take it in and have the transmission look at. Already replaced rear knock sensor because of SES light code.

Any help with this problem would be appreciated.

Thanks
Tom S.
Wells, MN