Humvee Transmission Problems

[Dock Rocker]

Hello guys I have an 89 m998 and I only have forward and reverse in HL and L . When in H it feels like it engages but when I give it gas I get noise from the rear end differential. Fluid is check and clean. Any ideas on where to start checking components???? Thanks ALL

Make sure the linkage is properly adjusted and that it’s not stuck between gears.

If not that then I bet you will be in the market for a torque converter and a transmission rebuild very soon.

I would check the linkage and if it’s properly adjusted throw It on a trailer and take it to a transmission shop.


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[tomelroy]

Something is broke in the drive train to or from the rear diff.

 

[Retiredwarhorses]

Bad diff, broken half shaft...this is how you limp a truck home when you loose any of those

 

[Gigrah]

Thanks guys, I thought it was weird that all of the other gears worked except the H . It just seems odd that in HL and L that everything is functional with no clanking when I applied the gas. Just thinking here, but if something broke like differential or halfshaft wouldn’t I be getting the same result in all the selections? I apologize for my ignorance or acceptance of facts but I can’t wrap my simple mind around how if a shaft or differential is damaged why would changing gears bypass said damage and allow you to limp back? SEMPER FI!!! And thanks to all that jumped in to lend a hand in my debunkle..

 

[Action]

When in H, the power will follow the path of least resistance, which could be something broken. When in HL or L, the transfer case will send some of the power to the other end of the HMMWV.
An example of this is if you jack one wheel off the ground, put in in gear and H. You will not move, but the tire will spin.
Have someone get in a put in in gear in H while you crawl underneath and look for what is spinning and making noise.

 

[OperationDesertSand]

Hi all, I dont think I have the rights to post a new thread so I will ask in this thread since it seems similar. My 1038 has been working and driving great. Then all the sudden yesterday when I put it in drive(after reverse) it wont engage and if I put the pedal to the floor I only hear the engines rpms go up but with no vehicle movement. Reverse works great, when I shift to neutral I hear the transmission change, when I shift to drive I don't hear any transmission change, when I shift from drive to 2nd I hear the transmission change and 2nd works great and when I shift from 2nd to first I hear a transmission change and 1st gear works great. I usually have it in H. I dont know too much about the transfer case settings so not sure if I need to try something more with that. Also transmission fluid looks great and is full. Thanks all for your help!

 

[Dock Rocker]

Hi all, I dont think I have the rights to post a new thread so I will ask in this thread since it seems similar. My 1038 has been working and driving great. Then all the sudden yesterday when I put it in drive(after reverse) it wont engage and if I put the pedal to the floor I only hear the engines rpms go up but with no vehicle movement. Reverse works great, when I shift to neutral I hear the transmission change, when I shift to drive I don't hear any transmission change, when I shift from drive to 2nd I hear the transmission change and 2nd works great and when I shift from 2nd to first I hear a transmission change and 1st gear works great. I usually have it in H. I dont know too much about the transfer case settings so not sure if I need to try something more with that. Also transmission fluid looks great and is full. Thanks all for your help!

Have you checked the shift linkage to make sure the shifter is actually putting it into drive?


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[Retiredwarhorses]

Also check and make sure you don’t have a broken half shaft or you Tcase is in neutral

 

[OperationDesertSand]

If I can shift into R,N,2,1, wouldn't that mean the shift linkage is fine?

 

[OperationDesertSand]

Hey thanks for the repsonse! Would you be able to explain how I can check those? I have minimal experience with this.

 

[Dock Rocker]

Hey thanks for the repsonse! Would you be able to explain how I can check those? I have minimal experience with this.

If you have an assistant that can hold the breaks you can go under and manually actuate the shifter on the transmission. You may need to unhook the linkage in order to do this. Look to where the linkage attaches to the body of the transmission. If the transmission drops into drive you know it’s the linkage or the shifter.

Do not try this without someone in the drivers seat holding the brakes. Even if you have the park brake set. If it moves it will roll over you.


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[OperationDesertSand]

Hey guys I just realized I made a rookie mistake in driving around on dry pavement in HL. Am I supposed to have it in H? It was working great with no issues to report. Now I'm scared I might have thrown a short shaft like the other post said. If I have a broken short shaft would I still be able to go in reverse, 1 and 2nd just fine? Because I can.

 

[OperationDesertSand]

So I went under the humvee and checked the linkage. It looks good. I also saw it move the transmission shifter. Does anyone know if the transmission ever has issues because of a bad ground? I'm wondering if the transmission controller could be out of wack because of a bad ground. I do notice that I have some electrical issues like only high beams working, turn signals are doing a quick strobe, when first starting, the engine is pulsing and the gauges pulse along with it. I plan on getting the grounding kit and installing next.

 

[Dock Rocker]

So I went under the humvee and checked the linkage. It looks good. I also saw it move the transmission shifter. Does anyone know if the transmission ever has issues because of a bad ground? I'm wondering if the transmission controller could be out of wack because of a bad ground. I do notice that I have some electrical issues like only high beams working, turn signals are doing a quick strobe, when first starting, the engine is pulsing and the gauges pulse along with it. I plan on getting the grounding kit and installing next.

If you have a 3 speed transmission (I think you do) there is no controller it’s completely mechanical.




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[OperationDesertSand]

Update, I put on the grounding kit and no change. In H the transmission has 1st, 2nd, and reverse but wont move in drive. I took it to the repair shop and they say I need a new transmission but without any real evidence. Last time it drove there was no weird noises and when I drive it there are no weird noises coming from the transmission. Any ideas of what it could be or what I could try instead of paying $1350 for a new transmission? Thanks all, I feel hopeless right now.