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Thread: Getting the HMMWV ready for summer

  1. #1
    Join Date
    Apr 2016
    Location
    Etna
    Posts
    13

    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
    Posts
    13

    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
    2,574

    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
    Present-2008 Rubicon, uniden pro xl520 cb, 5' wilson Silver Load, JCR engine skid, JCR evap skid

    Buy a Gazetteer

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