HMMWV Transmission selector difficult to go from Drive to Neutral

Hi guys,

Having a problem where the Transmission selector has been getting harder to move from Drive to Neutral.

I've had a look through the TM's and I'm going to start with the selector box, hoping when I take it out and clean everything it'll sort it. Hoping it's a sticky shaft, down from the selector button.

Has anyone else had a problem like this? Appreciate any pointers.

The transmission oil and filter was changed a few months ago, dirty inside when I took the Transmission filter out, but no debris. M998 6.2l with 3 speed transmission.

Many thanks,

Sarah

Have you checked the linkage between the shifter and the transmission? It could be in a bind.


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The linkage looks fine and is not binding.

In that case I would pull the shifter out of the truck and clean it well and put a good dry lubricant on the moving parts.


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I'll do that, would one of the bicycle dry chain lubes he okay?

Is the tranny itself binding?

What do you have? Three or four speed tranny?

TOBASH said:

Is the tranny itself binding?

What do you have? Three or four speed tranny?

Click to expand...

You can confirm by unhooking it from the transmission and cycling the gears.


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I will try cying the gears. Will I feel anything like a notch in each gear?

Three speed transmission.

Should be a detent or notch for those across the pond for each of the selected positions. Transmission control at trans may be a little stiff when turned by hand or jerky when pushing / pulling on the control linkage. Hand shifter disconnect of course.

Shifter locking positions of 1,2,D,N,R or P MUST track the same detent of transmission for the selection of 1,2,D,N,R or P. (if you got a park?) May have to count the detents to learn the positions. There may be a little slop or backlash in the control linkage between the two but not much. (it's made that way)

All together run the shifter back and forth to see that you are hitting the all the centers of detents or the "sweet spots" on transmission. Work from a good, locking into position shifte . Adjust linkage back to the transmission control. There is no adjustment on the shifter, the locking /indexing is fixed with NO backlash.

Somewhat same goes for the transfer case controls.

Check and set them both to be sure. Usually take two people. One shifting up top, one in the dirt, the smart one doing the science.

It is what it is....

CAMO

Thanks for your help guys. I'm up at my Humvee later this week and I'll keep you appraised of what I find.

Best wishes,

Sarah

Apolgies for not concluding the thread sooner. I've done a conclusion below as it could be useful to someone else in the future.

I did as suggested and disconnected the Transmission linkage (tape was put on the trunnions on the two linkages so they would not move). The Transmission linkage moved nicely, with a slick and positive selection of all the gear positions. The gear selector was definately the problem, as it was very hard to go into neutral.

I undid the four fasteners and took the selector box out. The big rubber boot on the lower part of the selector box had a big split in it and there was a lot of mud and dirt inside. The Neutral safety switch was dirty and very stiff to operate. This was the reason it was hard to get into neutral as the gear selector shaft was having a problem pushing the ball part of the neutral safety switch.

I tried cleaning the neutral safety switch, which helped a bit, but was still stiff in operation. I ordered a new rubber boot and neutral safety switch, then stripped the selector box completely to give it a really good clean. The gear selector push button was a bit dirty and rusty on the shaft, this was cleaned with wire wool and a dry lubricant applied. The gear and transfer case shafts were also very grotty, so were rubbed down and sprayed satin black.

When the parts arrived the selector box was reassembled with the new parts and refitted to my Humvee. The registration of transmission selection to the gear selector was checked and found to be fine. The button on the gear selector was a lot easier to move and neutral was now very easy to select. Very happy now and glad it wasn't a transmission problem