I've got a 92 C2500 5.7l and within the past 2-3 months i have noticed when going down the highway it refuses to shift into i would assume to be over drive, tho at times it will shift and cruise at about 1700rpm but on the times its not shifting its running at about 2000rpm, was wondering if anyone had any suggestions as to what could be causing it.

 

check the fluid level. If the level is good change the fluid and the filter, hopefully it will fix it if not you may need to buy a new torque converter.

 

most likely the lock up solenoid, easy to replace

 

You cruise at 1700 on the highway?!? I do at 2100 and I thought that was low.. maybe I have an issue with OD to?

70 mph correct?

 

Check and make sure the linkage is in sync with what the selector says. If you think you are in Overdrive where is the needle on the dash? completely on OD or D? Or in between? It has been known to happen, guys pull down on the selector lever and put it in D when they think they are in OD. Some guys dont even know what OD means or how to use it.

 

does it shift normal when doing everyday driving or have you noticed it alot softer then normal?

 

Yeah oddly enough once i got done doing a few fixes to the engine it started cruising at about 1700rpm but as of late it is cruising around 2000rpm sometimes when i am driving for awhile it will decide to shift and i will be cruising back down about 1700, i've got the filter for it but havent done it yet because i didnt have the right wrench to get the back few bolts off the pan since they are situated between the trani and a cross member for the frame.

 

most tranny problems are actually electrical, id look into changing the electricals in the pan, i did in mine and it fixed it

 

It is a 1992. It may not be electrical. 1993 was the changeover year. Some may be electrical some may not be, IF it is the original case.

 

hard to say with this truck, it seems whoever had it before me did some nice mods and other things they neglected horribly!