I addressed this issue back around the 6/05/05. I recieved many thoughts about hauling in overdrive pulling my 11000# boat, but I still am looking for answers to why I lost OD and 3rd while traveling down hill grade for 20 miles. My speed was 65mph, Tranny temps under 200F, eng temp 190F, EGT 800F. Everything going smooth. After approx. 18 miles down hill, I lost OD and 3rd gears. I pulled over and checked fluid. Fluid looked clean and did not smell hot.I proceeded on my way again and everything was and still is working normal again until last night it happened again. Now the samething happened again exept I was pulling up hill this time. 45 mph, EGT 1200, eng temp 200, tranny temp 245. I heard no suspious noises or had any warning anything was wrong. RPM's race to 4500 and I had no 3rd or OD. I pulled over, fluid looks and smells fine. I then proceeded up the hill, but this time had only Reverse, 1st, 2nd. I drove 40 miles in second gear keeping all gauges in normal limits. We got to a town, stopped for something to eat for an hour. We then proceeded again towards home 90 miles. The darn thing decided to shift into 3rd and OD when I could the rest of the way home. Does this sound like a computer problem, valve body, or pump problem or what? Any ideas.

Sounds like maybe a tranny limp mode. Runs okay after ignition off and back on again? If so, the ECM isn't likin' what it's seeing out there. 1200 EGT seems mighty toasty.

happened to a buddy of mine and it was his ECM. Oh course this was after changing the valve and a wiring harness out that they found the computer bad.

I went through the FAQ. Did not find ECM. How does this differ from the PCM? Where is it located and how much? Is it difficult to replace?

Vehicle speed senor and/or input speed sensors could be fouled with metal fragments, or the tranny is slipping a little.

ECM and PCM mean the same thing: The Electronic Control Module mounted behind the glove box. It controls the 6.5's little world.

Sincerely,

Rob

Vehicle speed senor and/or input speed sensors could be fouled with metal fragments, or the tranny is slipping a little.

The quantum mechanic speaks wisdom!

The reason I found this place (and that page) was because of a limp condition (WITH MY TRANNY, you sick bastards!).

No shift out of first unless you really overreved the engine, then a rock-hard shift to second and never a shift again. My speedo would also go to zero during these phases.

Replacing the transmisison output speed sensor cured that problem, after quotes ranging upto and including replacing the transmisison.

Cheap, simple $30 fix.

Tim

Where is the speed sensor located? Any idea how much to replace? As far as the tranny slipping. I have experienced this in the past with other trucks in the past. What I'm eperiencing now doesn't feel like it is slipping or shifting sluggishly. I have a gasser 99' 1 ton with the 4L80E tranny and it does slip some when shifting. The diesel shifts into all gears without hesitation and feels solid when it does shift. Especially when starting up a hill from being stopped, it runs through all gears now without slipping a bit and continues to climb.

what Tim is talking about is located in the tailshaft part of the tranny on the driver side, there is one bolt that hold a clip on that keeps it in. If that don't do it there is the 1-2 & 2-3 shift solenoids in the tranny but they are not too bad to change either, you have to drop the pan to get them.

Have you scanned it for codes? That might point you somewhere too. The ECM and PCM are the same, the main control for the truck.

I have not checked any codes. I don't have code reader. I will have to take it somewhere to be checked.

I have not checked any codes. I don't have code reader. I will have to take it somewhere to be checked.
Auto Zone will do it for free

Follow the FAQ stickey and pull the codes yourself!

Paperclip only works on OBD-I trucks (95 and earlier). After that you need the digital paperclip.