Transmission stuck in first.

[Dpsthomas]

Hello all,

I have a 99 Tahoe two door sport. I had the transmission rebuilt about two years ago. I haven't had any problems until now. I used four wheel drive for the first time two days ago with all the snow we've been having. Well yesterday while driving home (in 2 hi) I noticed it shifted a little stiff into second. A short while later it wouldn't go into overdrive. It stayed in 3rd most of the way home. Then, about a mile from home it suddenly went into first. Now it won't shift out of first. I tried selecting each gear but it just stays in first. Reverse works fine. I tested the TPS, it's working properly. The speedometer works so I don't think the VSS has failed. I replaced the brake switch on the pedal just to see if it was the culprit but that didn't change anything. Does anyone have any ideas about what I should check next? I'm thinking it's something electrical but I don't know where to look.

I should also mention that there was a lot of snow stuck up around the transfer case.

---------- Post added at 06:32 PM ---------- Previous post was at 05:52 PM ----------

I forgot to add that there are no codes present and the fluid level is good and is red not burnt smelling or anything.

 

[SunlitComet]

I am fairly positive your 1-2 shift solenoid is physically stuck in the on position. In automatic or manual selection. Other possibilites include a mispositioned or damaged space plate, or a goofy 2-4 band. The first two you can handle with a pan drop. to get access to the components.

 

[Dpsthomas]

Thank you very much for the reply. I've replaced a solenoid before so I'm confident I can give this a try.

 

[SunlitComet]

not such much the solenoid coil but the valve itself if coil ohm test is good. but in case you want to test at about 68°F it should read 20-40 ohms.

 

[Dpsthomas]

So I dropped the pan and pulled the 1-2 solenoid. They valve may have been stuck open. The solenoid fell out along with a good bit of fluid. I depressed the valve and spring, they seemed to move freely so I inspected the solenoid. The screen was absolutely covered in what can only be described as "gunk". It didn't seem to be metallic, more like deteriorated fabric or something. I cleaned it off thoroughly, along with the rest of the solenoids. I tested them and they all seemed to function properly. I thought about removing the valve body to clean it entirely but I was afraid of breaking something in the process. Then I replaced the filter and fluid. Hoping to have solved the problem. I bolted it back together and took it for a test drive. It shifted normally through 1-2-3 but reluctantly into overdrive. As I continued to drive the shifts became more and more reluctant. Then, it would only go as high as third, then only to second. Now, it may shift to second but then reverts to first gear. I hope this makes some sense. It's got me thinking that there's still a lot of "gunk" in there gumming up everything. Anybody got an idea of what's going on? Is it time to take it to a transmission shop?

 

[SunlitComet]

If you are up to it try cleaning out again even full valve body. If it continues then I strongly suggest going to a tranny for further inspection and take a big sample of gunk with you. As you describe it it sound like friction material or filter deterioration. But of course the filter should catch such things if it ends up in the pan instead mechanical parts.