Car when in gear will barely more or rev up?

Question

The situation as far as I know it. The Truck will move forward at a snails pace at normal revs, pedal to the floor the vehicle doesn't rev up or increase in speed. My initial suspicion was with the Transmission which was replaced. My second suspicion was with the fuel system, which has been troubleshot.
I considered the transfercase, but someone who I really trust with mechanics said otherwise and to look at the fuel. As if the engine is not providing sufficient force to turn the transmission or even rev up when in gear. What I've done so far. -Transmission has been replaced. Fluid replaced with filter.-Fuel Water separator replaced- Kick down cable adjusted manually adjusted and even replaced modulator for transmission.-transmission lever linkage checked
-Low fuel pressure (Before the fuel injection pump)checked 
-High fuel pressure (After the fuel injection pump) Checked.

If this sounds familiar, would love a little insight. I feel like I hit a wall in this project.

Jeffrey · Answer

As a military mechanic for over 30 years, I've worked on 1000's
 of HMMWVS.As you already know, there is no on-board computer, no sensors to go bad, no cat converter in the exhaust system to clog up.......being military it was exempt from EPA regs.My thoughts on your issue, first, low transmission fluid level......or two, bad torque converter. Top off the fluid level after the engine has warmed up and is running and see if that cures the problem.
If that doesn't cure it, go under the vehicle, remove the flywheel/torque converter dust cover, remove the 6 flywheel to torque converter bolts, push the converter towards the rear. There should be about 1 inch between the converter and the flywheel.
Start the engine and see if it revs and runs normally.
Good luck.

thebax2006 · Answer

WTF is the year make and model? If the throttle body is drive by wire the system my have lost the programming.and the gas pedal is not opening the throttle boy.

not · Answer

Restricted exhaust is a possibility. Transmission won't shift properly when it's partially restricted. When worse it runs, idles but makes no power to move. Eventually it can restrict to the point that the engine won't run. A backpressure test is in order, special gauge most people don't have; buy gauge and test. Or take exhaust loose before cat converters, make big loud exhaust leak and retest for normal power. Failed cat will be the restriction if it runs good without exhaust. Driving with bad running condition normally causes cat failure like this.

champer · Answer

First thing to establish is what the engine is like when it's in neutral. Does it start normally, idle normally and rev normally when you give it gas?  If it does, it's a transmission issue. If it doesn't it's an engine issue and that's where you should be looking.  It's always wise to establish the facts before you go throwing parts at it on the off chance.

CactiJoe · Answer

90 times out of a hundred, this issue is caused by low tranny fluid level. Usually more than two or three quarts low.

Anonymous · Answer

Year make and model.  Check for trouble codes.  Could simply be a bad TPS.

arther · Answer

you haven't said what it is so no one can help you? Does it have an accelerator cable or is it drive by wire? What codes are you getting why did you replace the transmission because the engine wouldn't rev?  I gather it has an accelerator cable since you say kick down cable but from what you've written you wont get any usefull help.

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Car when in gear will barely more or rev up?

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