ThirtyFive 21

Just checked in to a new unit and a couple vehicles are down due to not shifting. I've replaced (M1152) TCM, TISS/TOSS, pressed the reset button. I hook a supershifter into the TCM to manually shift and shifts without a problem. I Diagnosed with the Supershifter but no codes pull. Any ideas as to what it can be? The transmission light does illuminate.

Does your transmission light come on at all? If not pull the wires out of the reset button and plug them together if the light comes on the circuit breaker is bad.Also check your Throttle Position Sensor, if it is out of adjustment will prevent from shifting. One thing I would also check, it's amazing but I've seen it, the tiss and toss wires to make sure they are not switched around.

Transmission light does illuminate. I'm getting 12V to the reset button wires. I can't image the tiss/toss wires were switched around but anything is possible in this case. I'll follow up with an update if or when I figure it out.

Check the fuel line on the back of the engine leading into the fuel water seperator. If the engine was replaced there is a good chance they didn't cut it down to size and the fuel is being restricted at higher RPMs. This will cause the vehicle to seem as though it's not shifting.

The way to test this is by slowly bringing the vehicle to Wide Open Throttle (WOT). If the engine begins to sputter then it's a fuel problem.

Note** I've had issues further down the fuel supply line that have caused the same issue. There is a one way check valve in-line on the fuel feed that had a small plastic burr stuck in it causing the same issue as the above mentioned issue.

having some what of the same issue. just replaced the transmission and it wont shift out of 1st. now its just screaming down the road.

*also the speedometer isn't working as well, if that has anything to do with it. *

it wont shift out of 1st or is it stuck in 2nd?

I took it out on a road test, it shifted out of first and into second once. We stopped and turned around. Came back to the base and I tried to troubleshoot the speedometer. Now literally time now, I start it up and now it won’t move. The engine oil was low so we filled that up to specs. But now the damn thing won’t move.

Now I mashed on the pedal, in revesre. We are moving again for the moment, we are taking it on another road test.

Just got back from our short test drive. No joy. It still won’t shift out of first. Tried to move the transmission selector to D, 2, and 1 and it was doing anything.

do you have a tran-x? I think you actually might be in 2nd this whole time. need to know because that will make the difference.

also what kinda HMMWV?
did you click the reset behind drivers seat?