http://www.dieselplace.com/forum/smileys/Confused.gif hello , I am new to the PLACE , and fairly new to diesel trucks. I have a 93 chev 6.5l with what i believe is a 4l80e trans. THE PROBLEM I am having seems to transmission related. so here goes, when going down the road at 30 mph or more the speedo starts to drop out. it will bounce up and down and then usually it will drop to 5 mph or less and then i've got nothing but neutral untill the speedo jumps back up and then away we go , sometimes for a second and sometimes its good to go for the duration of my trip. this problem first started occuring last fall when temps started dropping but if i let the truck warm up for a good 15 to 20 minutes it was usually fine so i didn't pay much attention to it. now this summer with temps rising the problem seems to be back and more intense than in colder temps. it seems to become more of a problem after operating temps are up. although today i had problems right out of the chute. yesterday i only had minute problems even after about 40 miles of driving. i have been driving with a scanner connected and have detected no trouble codes but the output rpm drops to zero or near zero as does the speedo while this condition occurs. i have not noticed any other values dropping out . but the brake light will come on after this has been going on for awhile. i suspect ground issues. has anyone experienced any thing like this.





P.S. sorry so long but this is hard to describe in just a few words

A bad/corroded connection between the alternator and positive terminal or fuse block and fusable links will cause the RPM to read zero.

http://www.dieselplace.com/forum/smileys/Big Smile.gif I believe i found the problem to be a chafed wire from the main loom out of the tranny control. cleaning and tightening the connections of all power and grounds seemed to help also but it has not re occured since i found the wire. i m not sure what the curcuit is as i have not traced it down yet. thanks for the input.