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Thread: Getting the HMMWV ready for summer

  1. #1
    Join Date
    Apr 2016
    Location
    Etna, NH
    Posts
    28

    Default Getting the HMMWV ready for summer

    I pulled my 92 m998 HMMWV out of its winter slumber a couple of weeks ago. It had a major dental problem in the fall: the front diff lost some teeth. These have what is basically an amc20 diff with a torsen t-1 center, and the torsen got unhappy, and was the part that lost the teeth. When I bought the truck it had no oil in the front diff, so I'm not surprised it failed. There had been too many metal shaving for comfort when I changed the oil before. What I was surprised about is I had no idea it had failed until my fall maintenance routine when I discovered a tooth sticking to the magnetic drain plug along with the shavings. I was able to source a surplus diff over the winter which was cheaper than the parts to rebuild the broken one.

    Mine is an early model (known as an m998a0), but changes were slowly made through the a1 and a2 series, and finally what I think we run now: the "ecv" series. In any case, my new front diff had a larger yoke than my old one, which meant either replacing the yoke, or replacing the front part of the front driveshaft with a later one that can handle the larger yoke. Its relatively cheap and easy to replace the drive shaft (bonus is I get a new pillow bearing and universal) , and the thought of taking the pinion off and fouling up preload didn't appeal to me, so I'm waiting on my new driveshaft.

    In any case, it's in pieces in the garage. Have I mentioned very little on this thing seems to be symmetrical? The whole engine/trans/transfer case is angled and offset, and one brake caliper (they're inboard on the diff) on the front is at a different angle than the other.

    Other tasks include getting the e-brake to release properly again, which is important, since early HMMWVs have no park on the transmission, the th400 parking pawl not being considered strong enough.
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  2. #2
    Join Date
    Apr 2016
    Location
    Etna, NH
    Posts
    28

    Default

    Well, new diff is in the truck, which was a bit of bear. That thing isn't light, and there isn't all that much space. The new drive shaft hasn't showed up yet. I've got a few more parts on order including a new front left half shaft since the CVs felt loose in the old one. Even though I put the calipers back on (they're inboard and mounted on the diff) I'll probably order new rotors and put them in since the left hand one wasn't in great shape, and this is my chance while it's all apart. I sometimes feel I'm rebuilding this thing one part at a time.

    It's not really a hard vehicle to work on, but there are a lot of moving parts, many of which were tucked up out of the way on purpose, making them a bit harder to get to, or requiring the removal of more other parts than I would have thought. I often wish it just had live front and rear axles, but then it wouldn't be a HMMWV :-)

  3. #3
    Join Date
    Sep 2010
    Location
    Lebanon NH
    Posts
    2,725

    Default

    Lookin good, been keeping my eye out for it across the road ;)

    Sent from my SM-N910V using Tapatalk
    Gone now :( -2000 Jeep Wrangler Sahara, 2" BB, 4.88's, TT F&R, 33x10.5 km2's, xrc8 winch, uniden pro xl520 cb, 4' wilson
    Gone now too :( -2008 Rubicon, uniden pro xl520 cb, 5' wilson Silver Load, JCR engine skid, JCR evap skid
    Present-2012 JK Sahara-KO2's plus neat stock stuff

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  4. #4
    Join Date
    Apr 2016
    Location
    Etna, NH
    Posts
    28

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    Good to hear from you Bob! It will probably be a little while before you see me.

    The HMMWV is happily still apart in the garage, awaiting more parts.

    The new front driveshaft is in, and the front end is almost back together. I'm just waiting on brake rotors. After I get those in, it shouldn't take long to finish the diff replacement project.


    The parking brake cable replacement is ridiculous. The parking brake holds fine, but it doesn't release all the way, which then cooks the brakes. The HMWMV has an automatic transmission, but early models like mine have no park position, so you can see the importance of the e-brake working correctly :-) Right now, I have to run around the back of the truck, pull on a little lever on the right side caliper to get the parking brake to release all the way, pull the chocks, and try to run into the drivers seat before it rolls away. Not ideal.


    I'll give the engineers the benefit of the doubt, but to replace the parking brake cables, which are the problem children, I have to pull part of the exhaust. Of course, every nut and bolt related to the exhaust is rusted to pieces. I manged to get the exhaust out today, which took a few hours for about 10 fasteners. I sheared a bunch of them, and the others only came off as I had soaked all of them in penetrating oil for a day. I've got all new nuts/bolts for the exhaust on order, as the ones I took out shouldn't go back in if I ever expect to get it apart again. From the factory the HMMWV is all grade 8 hardware, mostly with all-metal lock nuts, and I'm trying to keep it that way. The hardware isn't expensive, but I sometimes have a hard time sourcing it locally.


    Probably another week or two, and it will be ready to go again. I'm trying to be smart (and failing) by keeping a list of the tools I need to add to my in-truck toolkit to bypass potential non-catastrophic failures, such as broken half shafts, drive shafts, etc.. The half-shafts are well known as drive train "fuses" for this thing. Three of the four half-shaft have been upgraded to heavier duty, later models from the 10k gvw trucks. They're plug and play replacements for my earlier 7k gvw truck. There is also a 12k gvw model, but retrofitting parts from that gets more in-depth than I want to go. The curb weight on this thing is only about 5,200 lbs.


    Quote Originally Posted by bob View Post
    Lookin good, been keeping my eye out for it across the road ;)

    Sent from my SM-N910V using Tapatalk

  5. #5
    Join Date
    Apr 2016
    Location
    Etna, NH
    Posts
    28

    Default

    The weekly forum group therapy update on the HMMWV :-)

    The front differential is all back together and ready to go. I discovered there quite a bit of backlash in the the front right portal gearbox, so that now goes on the list to rebuild. Not critical (I don't think it will fly apart), but should be done. I feel like I'm living a modified version of the Johnny Cash song One piece at a time. In my case I rebuilt it one piece at a time. The joys of owning an older piece of machinery that was used by a new group of 18 year olds since 1992!

    Still waiting on parts to put the e-brake and muffler back together. The parts supplier I use is normally quite prompt with shipping but has slipped these last couple of times. I ordered the newer model e-brake brackets that should prevent the rear control arms from crushing the cables.

    I fully intend to show up for the anniversary run. I think I'll probably do the novice/beginner run again since I don't have proper rock rails and undercarriage protection yet, and I'm cautious because of the width and lack of articulation and relatively cruddy military tires. On the other hand it has 37" tires, 16" of clearance, a nice Mile Marker hydraulic winch (put that on after I got well and truly stuck in the mud), and torque biasing diffs, so maybe I can be convinced into an intermediate run.

  6. #6
    Join Date
    Jul 2017
    Location
    New Jersey
    Posts
    63

    Default

    do you want to buy a snow plow frame for it?

    back in 93 I bought the sixth humvee to be sold in the civilian market in NJ

    owned it and drove it for about 15 years -- I was a snow plow contractor so I designed and built a snow plow frame for it -- I pushed a 8.5 foot Meyers snow plow with it -- it was desert storm time so I had the plow painted desert camo

    that truck could push snow

    it was the original design to hit the civilian market -- 6.2 gm diesel with a 3 speed transmission -- soon after they went to the 6.5 and 4 speed

    truck was awesome at what it was designed to do

  7. #7
    Join Date
    Apr 2016
    Location
    Etna, NH
    Posts
    28

    Default

    I'm tempted, but the military version that I have isn't the best winter vehicle for my purposes. Too little insulation, too little rust protection, and too little heating system until that thing has run for a LONG time. For the moment I'm treating this as a three season vehicle, and it goes to live in a friend's garage over the winter, as I don't have a protected space for it at my house, much less it and a plow :-)

    Quote Originally Posted by Heavyopp View Post
    do you want to buy a snow plow frame for it?

    back in 93 I bought the sixth humvee to be sold in the civilian market in NJ

    owned it and drove it for about 15 years -- I was a snow plow contractor so I designed and built a snow plow frame for it -- I pushed a 8.5 foot Meyers snow plow with it -- it was desert storm time so I had the plow painted desert camo

    that truck could push snow

    it was the original design to hit the civilian market -- 6.2 gm diesel with a 3 speed transmission -- soon after they went to the 6.5 and 4 speed

    truck was awesome at what it was designed to do
    Last edited by uvwanderer; 04-29-2018 at 05:40 PM.

  8. #8
    Join Date
    Jul 2017
    Location
    New Jersey
    Posts
    63

    Default

    The civilian version had a second heater in the rear -- Was a box, with heater core, fans, and controls -- I believe it was just blower controls and not temperature controls for the rear system

    It might have been a factory recall or upgrade but I remember they installed it after I had already owned it at no cost to me -- Might even have been AC too, I don't remember

    Would be easy to build a secondary heating system -- put it right on the drivetrain hump between the rear seats

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