Need help with tranny or transfer case issues please

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Valleyordnance

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Hi Guys,

Need some input on a problem I'm having with my '95 M998, 6.5 w/3L80e Trans.

Shifting into drive with the t-case in H, the truck acts like the E brake is on, takes a lot of pedal to get it to move. Jacked up the front and rears to see if the brakes were dragging, all wheels spin freely with no noises. Gave each half shaft a good look and tug to see if they were broken, all good.

Changed tranny fluid and filter, replaced fluid with Dex III. Still same results.

If I put the transfer case in HL it moves a little better, but still real sluggish.

Could use a few clues on where to look now if anyone cares to jump in.

Thanks

Chris
 

Bulldogger

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Curious. I don't have an answer, other than complete spitballing. But I'm interested to hear what comes of this thread.
I guess I'll offer the idea to check your linkage for the transfer case shifter. Investigate inside the boot for foreign objects and check that the connections/controls between the shifter and the TCase are not being interfered with or loose.

I had an old Jeep that was sluggish and complained about shifting into 4WD. My theory was that it had been driven too long without using the 4WD gears of the transfer case. Doesn't seem likely to be your issue.

BDGR
 

Bulldogger

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Sue raises an interesting point. Have you used Lock often and if so did you perform the 50’ reversing maneuver to relieve drivetrain tension? Seems like a simple thing, but it makes a difference.
Bulldogger
 

Valleyordnance

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Sue raises an interesting point. Have you used Lock often and if so did you perform the 50’ reversing maneuver to relieve drivetrain tension? Seems like a simple thing, but it makes a difference.
Bulldogger
New to me truck - Bought it about a year ago, just finally getting a chance to mess with it.

Chris
 

Bulldogger

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Try finding a place to back up 150’ to be sure the differentials are stress relieved. They could be bound up.
I’ll Bulldogger
 

Valleyordnance

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Try finding a place to back up 150’ to be sure the differentials are stress relieved. They could be bound up.
I’ll Bulldogger
Jacked up one end at a time and free spun the wheels to ensure the brakes weren't dragging. Should have released any windup.

This isn't my first HMMWV - Just the first one I can't figure out....

Thanks for the suggestion though, keep them comming. I'll figure it out sooner or later.

Chris
 

Katavic918

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Does it coast freely when you let off the throttle, such as down a hill, or does it slow down like something is dragging/binding? I assume the engine revs freely when in neutral? Does it seem like the engine is under load or slipping when trying to accelerate? Just trying to get a better picture of the issue. A video might help if you can.
 

Bulldogger

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I'll throw out another potentially silly question: did you happen to replace the rear brake pads, and NOT readjust the free play in the parking brake assembly (leaving the rear brakes partially engaged)? Happened to me.
BDGR
 

Valleyordnance

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I'll throw out another potentially silly question: did you happen to replace the rear brake pads, and NOT readjust the free play in the parking brake assembly (leaving the rear brakes partially engaged)? Happened to me.
BDGR
No - haven't messed with the pads on either end yet, there looks to be better than half a pad left. Like I said I jacked up each end of the truck and free spun the wheels to make sure there was nothing dragging.

my other Hmmwv's will want to crawl if you put them in Drive with the brake off and no gas. I need to give this guy half a pedal to get it to move. I figured it might be torque converter, but from what I understand they either work or they don't. Is that the case?

I haven't had a chance to take it out to drive yet so I don't know about coasting it. I'm paranoid I'll break something if there is a problem already.

Going underneath today to check stuff out.

Chris
 

Bulldogger

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Hmmm. My own HMMWV needs prodding to move, though it sounds a nit better than yours. We may have the same problem, though it sounds like yours is worse than mine. I attribute my lack of get up and go to my HMMWV coming from the MD National Guard who do not seem to have given her the best treatment. Radio antenna holes all over her indicate a potential for a lot of idling while running comms rigs as well.

I've been hoping a rebuild to the 3L80 will help, but also need to run a compression test too.

BDGR
 

sue

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Find 50’ or so of area that you can drive slow with
zero (0) brake application, again zero. Then slide
under and
and check disc temperature. Easy way to see if
a brake is the problem.
 

REF

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Building on Katavic,s thought, Place trans and transfer in neutral and roll the unit, your choice by hand/hill or tow rope. if it still rolls freely shift transfer case into High and see if there is a big difference, if their is I would look at the transfer case if not I would look to the trans.
Hope it helps
 
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