A leak from the front of the transmission would be caused by three things. Bad pump bushing, pump o-ring, or pump seal. You will have to pull the transmission to find out which. There is a video about how to pull a pump without a pump puller on youtube, but you will have to drop the pan as well to do it that way.

 

My 2003 1500 silverado used to 70 mph at 2100 rpm. Last night it was turning 300 rpm at 70. Recently dropped the drive shaft to replace rear u joint . Any ideas HELP.

 

Scan it for codes, if there is one that would give you direction where to look.

 

no check engine light was on . Seems thst it would go to reduced power mode

 

Not really sure, i hate the fact that no code popped up, you may want to look at scan tool data while your having the problem. How often does this happen? What scanner are you using, snap-on? Gary

 

My 99 Silverado with a 5.3L had the same issue. My mechanic pulled the shaft and welded the seal/hole. Haven't leaked tranny oil since.