Hi All,

Transmission problems seem to be my issue today.

Last night on the way home from work my 98 Suburban diesel 4X4 2500 would not shift out of second gear. This happened climbing a fairly low grade. The truck simply refused to shift to 3rd the rest of the way home. Frist to second shifts were smooth Thankfully there was lots of traffic and driving at 35mph was not such a big problem. I believe I have the 4L80E transmission.

When I got home I checked the transmission fluid and found it to be low, (bottom of dipstick) No visible leaks, but a bit hard to see as the truck underbody is cover in snow and ice.

This morning I took it out and 3rd gear was working fine. I stopped to get some more transmission fluid and added ¾ of a quart. Everthing was still ok but in about 5 minutes of driving the no 3rd gear problem was back. I continued driving as I was in stop and go traffic and in about 5 more minutes it was shifting into 3rd again. I made it to work with the problem coming back, she is now parked for the day.

Over the last few weeks I have noticed an occasional delay in the shifting from 3 to overdrive. Also for the last several months I have had on and off issue with hard shift from 1st to 2nd I am not sure if this is a related problem or a separate issue. The truck sometimes give a clunk from 1st to 2nd other times it is smooth as it should be.

Can anyone give me some ideas what to check before heading off to the transmission shop. The tranny has about 135000 miles on it.

#1 Connections.
#2 internal wiring harness in the transmision.
#3 Sticky transmission solenoid or shifting valve that it commands going into third.

Pull codes so we can stop guessing. But my guess is, 1,2,3 and not necessarily in that order.