Hello All, im new to this forum and I am fully restoring a 1995 hummer h1 with a 5.7 GAS engine TBI.


A little background:

I modify exotic cars for a living so I am pretty mechanically inclined, however I am not a mechanic.
so the car came to me not running, turned out to be a simple fix (drain plug in gas tank was toast so tank was empty (haha) I also rebuild the throttle body with new injectors. and she runs! I tore the care down completely and sent it out to Line-x for a full liner and re assembled the car with every single part brand new. so she looks GOOD.

As I never driven the car more than just around the block a few times after getting it running, I don't really know if the problem was there before or not. but I do not feel like it was.

long story short, the car will not shift, just stays in one gear (assuming 2nd) I removed and cleaned the speed sensor (will replace soon after getting some input). Fluid is good.

My question is (and I've searched for days) would a disconnected speedometer cause the transmission to not know vehicle speed, thus causing the shifting problem.
I put all new speed hut gauges and the speedometer works off GPS and is not actually connected to the VSS signal.

any input would be greatly appreciated as I don't want to just throw new parts for no reason.

and no intro is good without photos!

 

there is two sensors on transmission that the hummer h1 uses them both. Has this transmission been changed or is it original to truck
thx

 

as far as I know its original, nothing looks out of the ordinary or modified. however looking under at the two sensors there was a previous hack job on the wires for those sensors. (will post photos) I temporarily re did the wires to see if it would fix the issue as the old wires were melted and in rough shape I was suspecting a short. (maybe a short happened while I was tinkering with the wires and caused a fuse or the sensor itself to go bad? however it did not fix the problem. also I noticed one sensor on the transmission that is not plugged in and does not even have wires, or a plug, to plug it back.

the only issue is I don't believe the car has this issue when it came to me as I remember going down the street at 60mph comfortably and now I can't even touch 50mph without feeling like the engine is going to blow. it is either a coincidence OR it has something to do with me changing the speedometer?

if I can rule out the speedometer causing this I will go ahead and change both those sensors.

 

will be taking it to a reputable repair shop tomorrow so they can scan it. (obd1 with obd2 connector) my obd2 scanners all do not communicate with the car.

really hoping the speed sensor just took a crap on me coincidentally while I was working on it. rather than the speed hut speedometer and rpm gauge causing the problem


any input would be greatly appreciated.

 

Sir I have this same issue and have spent over $1500 trying to solve this puzzle. I've had my military H1 for over 2 years and finally I had to put it away in my storage before I put it out in the street **** on it and set it a fire. I've several transmission shops look at it. If you have had some luck with getting your issue resolved I sure would like to hear what it was. Sounds like it is the same thing. Not positive but it sure sounds the same cuz I did just about everything you did and more. Anyway, I sure would like to get old Betsy out of the storage and go for a rip. Good luck. My email address is kingpin2000@me.com if you want to contact me directly. Take care. Kelly P Fort Worth, TX

 

Call Mike Sabaresse at Tustin GMC. He is the finest H1 mechanic in the country and also works on a lot of HMMWVs.