M998 wont shift out of 1st--any ideas

M998 wont shift out of 1st--Maine rebuild with 5k miles--6.5 gep--Fluid is at correct level and is clean--in low range at high rpm does not shift--on highway in hi range no shift either--reverse is ok and the shift from neutral into 1st feels solid-- --It has sat for 2 years in my garage--I may have purchased it not shifting--only now had time to play with it---Any ideas what might make it shift--thanks George

Have you checked the shift linkage?

If the linkage is good drop the pan and see if it’s full of metal.


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gem1410 said:

M998 wont shift out of 1st--Maine rebuild with 5k miles--6.5 gep--Fluid is at correct level and is clean--in low range at high rpm does not shift--on highway in hi range no shift either--reverse is ok and the shift from neutral into 1st feels solid-- --It has sat for 2 years in my garage--I may have purchased it not shifting--only now had time to play with it---Any ideas what might make it shift--thanks George

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Which transmission do you have? 3 or 4 speed?

3 speed in this one

Vacuum modulator? Sure will cause this problem.

No vacuum on Hmmwv. Uses a cable pull control.

CAMO

What is the adjustment for the modulator cable--I have 6 threads shown at the rear of the adjustment up by the engine

Milcommoguy said:

No vacuum on Hmmwv. Uses a cable pull control.

CAMO

Click to expand...

And maybe the cable is broken in the conduit. Pull the end that's in the transmission and see if the plunger moves when soldier b presses the gas pedal.

ok--can look at that tomorrow--do you know the adjustment spec--thanks

A bad governor can cause the vehicle not to shift properly. Kits are inexpensive online and the job can be done in the vehicle. There is a plastic gear inside that can fail along with some springs that can let go or it can just be gummed up from inactivity. TM 9-2320-280-34 section 7 talks about governor repair.

Here's how to check the governor valve: hold it by the plastic gear, and snap the weights in and out while watching the inner valve. It should be sliding up and down. If it's stuck, drive the 1/8" roll pin out, pull the plastic gear out, and then pull the valve out. Clean it out, lube it with WD40 and make sure it's free when you put it back together

youtube link: https://www.youtube.com/watch?v=-0Ry1Z92CGk

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Pull dip stick look in sunlight or flashlight and look for glitter, smell of burnt fluid. If you see metal next step R AND R. But as been said that since there is no vacuum source then cable adjustment, or has fallen off at contact points. Although it is possible the governor does stick, springs corrode fall out, gear pin or breakage, helps tailor shift points. Sticking valve body, again rarely but does happens.

Do not get abusive just probably a simple fix. As Dock Rocker has said also, I WOULD pull pan anyway for piece of mind if you have never had the trans pan down anyway, just for observation at the very least.

Hey guys, just an update on this since I'm the one that bought the truck. I brought it to the trans shop and it turned out the kick down solenoid broke apart. The guy said he's been doing this a long time and had never seen that happen.
All is well except now I want to do an overdrive conversion since I hate hearing the poor engine scream over 40mph lol.

Mike

Good to hear the issue was resolved. I’m with you in the overdrive. It’s like I’m reentering the atmosphere anytime I go above 45-50mph.