New Member & New Truck

[DLJIII]

Hello Everyone,
I have had a draw to humvees for a long time but, I never took it seriously enough to consider buying one.
Honestly, I never thought it was possible.
Well, today I bought one.
1987 HMMWV 998, 31,000 miles, soft top, four door, soft door, canvas cargo cover.
Road legal title, tuned up and well serviced recently.
The truck was a national guard depot truck issued specifically for a LT. WARD.
New LED headlights, new crew and cargo cover, professional serving and overhauling or major systems.
It runs great, feels great and served me very well on my first drive ever three hour drive home.
I will post pictures below but, I paid $13,500 for it.

Now, I have a few questions and I am sure they are very stupid questions.
This is a chance for everyone to share their wisdom, experience and passions with me.

Every once in a while the engine will increase RPMs and the volt indicator will hit red line.
I am assuming that is the engine charging the batteries but, am I right and how often should this process occur?

A few times at low rates of speed 5-10mph with a turn or slight direction change, I could hear a loud thumping sound coming from the rear drivers side tire.
My first guess is a U joint but, I could be wrong. If it is, will the repair be major or minor and is it costly or not too bad?

How big is my gas tank and what type of mileage can I expect? The guy I bought it from put $10 about 2.5 gallons in and I topped it off not long after with about 11 gallons. It covered about 180 miles and the gauge shows about 1/3rd of a tank. I have to assume this is completely wrong, two thirds of 13 or 14 gallons pushing 7,700lbs 180 miles. Does type 1 or type 2 go go juice work best?

Can the cross bar behind the drivers seat be removed? I would like to mount the seat a little further back, I can beef it up and replace the structural properties of the arm. I can rivet, weld, bond and fabricate what I need to make up for any losses there.

What kind of converter / inverter is best for creating an additional 12v system from the 24v system? I plan to install some basic electronics but, they are all 12v. So, I need to establish a 12v system first.

Ok now this one I am dying to hear.

What upgrades are a must?
What should I do?

I am not a mechanic but, I have converted an old school bus into an off the grid home and wired up enough crown vics in the middle of the night to feel comfortable fabricating what I need, deconstructing everything else and wiring things back together. Plus the most important part of experience, knowing when I need to hire it out.

Thanks, here are a couple of pictures.

 

[Postman515]

When starting it cold the glow plugs will cycle for a few minutes making the alt gauge jump some. If your in the red driving you need to put a voltmeter on the batteries to make sure your not overcharging. WOn't take long to burn everything out if its putting out 30+ volts. It will cook your batteries in minutes and possibly take out your pcb, gauges, etc.

 

[Tracer]

Nice looking truck! Also welcome aboard from Nevada.

 

[Bravojmc]

Very good looking truck! Welcome aboard from Western Colorado!

 

[dmetalmiki]

Welcome to the site, hobby, friendships, and events to come. Which you will most certainly enjoy with your newly acquired and very smart looking truck. Inside and out.

 

[ryanruck]

Nice truck! I'll throw my $0.02 in...

Every once in a while the engine will increase RPMs and the volt indicator will hit red line.
I am assuming that is the engine charging the batteries but, am I right and how often should this process occur?

This doesn't sound normal. As Postman said, if you're overvolting it could burn stuff out. Maybe a bad voltage regulator?

If it is, it may be worth replacing the entire alternator with one of the newer dual voltage ones which would help solve your question below about 12v accessories. The dual volt alternator will allow you to draw 12v off the rear battery but will keep it charged.

How big is my gas tank and what type of mileage can I expect? The guy I bought it from put $10 about 2.5 gallons in and I topped it off not long after with about 11 gallons. It covered about 180 miles and the gauge shows about 1/3rd of a tank. I have to assume this is completely wrong, two thirds of 13 or 14 gallons pushing 7,700lbs 180 miles. Does type 1 or type 2 go go juice work best?

Should be a 25 gallon tank. I haven't measured exactly but I guestimate I get about 12MPG average. Also, you should be weighing in at around 5,200-5,500 lbs. 7,700 would be the gross vehicle weight. For type 1 or type 2, I just use whatever they've got in the pump. I do add Diesel Kleen to each tank to make up for the ULSD.

Can the cross bar behind the drivers seat be removed? I would like to mount the seat a little further back, I can beef it up and replace the structural properties of the arm. I can rivet, weld, bond and fabricate what I need to make up for any losses there.

I've seen a number of different solutions. Some people notch it and box the brace. Some people remove it entirely.

What kind of converter / inverter is best for creating an additional 12v system from the 24v system? I plan to install some basic electronics but, they are all 12v. So, I need to establish a 12v system first.

Easiest and closest to factory way would be the dual volt alternator I mentioned. No inverters or transformers you have to worry about getting wet.

Ok now this one I am dying to hear.

What upgrades are a must?
What should I do?

Personally, here's what I think of as "must dos".

- LED headlights at the minimum for much improved visibility at night (which you've already got) but all external LED lighting for good visibility to other drivers since it is a camo truck.
- Upgraded seats. I've got MRAP seats in mine. Couldn't imagine riding on those glorified stadium cushions all the time. You'll need to upgrade the driver's seat mount to the high back style and the heavier battery cover/seat base for the front passenger. The existing rear ones will work with a little reinforcement but there's heavier duty ones if you want.
- Since you're in Minnessota, a heater upgrade might not be a bad idea. I upgraded mine to an MRAP heater and added rear ducting and, it will turn the cab into an oven! Heater is NSN 2540-01-554-3505. You can find them on eBay. I did a short write up on here in a thread.
- A rear airlift bumper is a good idea since it seems like people inexplicably love to tailgate these trucks. A little extra insurance to protect you is a good idea.

 

[DLJIII]

Thank you for the warm welcoming Dmetalmiki, Bravojmc, Tracer, Postman and Ryanruck.
I certainly appreciate the advise and I will be fixing or getting them addressed.
25 gallons seems much more realistic and 12mpg is not bad at all. I had a 68 C10 chevy as my daily runner and I was getting 7.5-8 mpg in an old standard pickup.
I actually sold it gassing it up, an older gent walked up complimented me and made an offer that I could not refuse.
Check cleared and he picked it up the following evening.

My truck needs work, generator needs attention or replacement. The braking system needs work, the parking brake works fine until you are pitched nose up or down and it gently slowly lets an inch out at a time. I noticed a sway or lurching at a red light after I made his thread, the approach was fine and once the vehicle came to rest there was slack when holding the brake. A very slight roll forward and back before it would completely stop.

I am glad to hear the cross bar can be worked with and a new seat can be installed. I am 6'6 and 300lbs so I could use every extra inch but, surprisingly the half seats and foam was comfortable for me. The distance from the seat to the pedal was my biggest issue, a man who spends 10+ hours a day in a Crown vic nearly dies when squeezed into close foot pedals. Those lovely little muscles you forget you have until they are unhappy.

Ok, immediate priorities are transfer title, insurance and paperwork.
Set up an appointment with my diesel garage to look into brakes, alternator, rear wheel thumping.
I want to install a tach, digital battery volt monitor and start planning door fabrication.
Thanks again for the help, feel free to push me in the right direction.

 

[ryanruck]

My truck needs work, generator needs attention or replacement. The braking system needs work, the parking brake works fine until you are pitched nose up or down and it gently slowly lets an inch out at a time.

Have you tried adjusting the tension on your parking brake lever? Turn the top clockwise to tighten, counter to loosen. Don't overtighten.

I noticed a sway or lurching at a red light after I made his thread, the approach was fine and once the vehicle came to rest there was slack when holding the brake. A very slight roll forward and back before it would completely stop.

The rocking on coming to a stop is normal on most of these trucks. Just part of the geared hub design. The new style geared hubs don't do that though.

 

[ageregunner]

Very nice truck. Welcome to our hobby from PA.

 

[DLJIII]

Thank you Ageregunner.

Ryanruck, I had no idea the parking brake had a tension selector. I will give that a go this morning, small adjustments, quarter turn type of thing.
Ok, good the resting braking is normal.

Haha, I told ya I was brand new to this.
I appreciate the help and greetings from everyone.
I woke up an hour early today just to get driving and all the paperwork moving.
Thanks

 

[Wire Fox]

Have you tried adjusting the tension on your parking brake lever? Turn the top clockwise to tighten, counter to loosen. Don't overtighten.


The rocking on coming to a stop is normal on most of these trucks. Just part of the geared hub design. The new style geared hubs don't do that though.

Really, the new hubs don't do that? I'm actually very interested in that down the line, then. I don't need the extra strength or necessary the supposed noise reduction, but the rocking I'd like to be without...

 

[Bravojmc]

I like that feeling at stops! It just reminds me every time that I'm driving my favorite vehicle!

 

[ryanruck]

Really, the new hubs don't do that? I'm actually very interested in that down the line, then. I don't need the extra strength or necessary the supposed noise reduction, but the rocking I'd like to be without...

New ones on the left are helical cut and are supposed to run quieter and keep the truck from rocking on stop. Original design on the right.

Personally, like Bravojmc said, I like it since it's unique to these trucks.

 

[Retiredwarhorses]

Thank you Ageregunner.

Ryanruck, I had no idea the parking brake had a tension selector. I will give that a go this morning, small adjustments, quarter turn type of thing.
Ok, good the resting braking is normal.

Haha, I told ya I was brand new to this.
I appreciate the help and greetings from everyone.
I woke up an hour early today just to get driving and all the paperwork moving.
Thanks

I highly suggest downloading the -10 operators manual on this site.

 

[DLJIII]

Ok, I tested the charge voltage. Idle sits about 23.6 to 24.4 volts, when the engine kicks in and hits the generator the voltage spikes to 30.4-32.8 volts for any time between five seconds to 25 seconds.

The two batteries are dated 05-16 so they are newer than I expected.

My insurance company told me to come back later when they figure out how to insure it and in order to get a title transfer I need insurance so right now I am waiting but, not worried.

I will look into the replacement alternator tonight after work and I was hoping someone could shine some light on the rear wheel noise.
A chunking, thumping, flat tire sound at a low rate or speed and during turns or shifts in weight you can hear it vibrate.
What are the possibilities and how much can I expect to spend fixing a barring or U joint or what may be the cause?

Thank ya. I love my truck by the way, I am normally a speeder but, I certainly dont mind cruising a whole 47 mph. It feels very optimal for the truck for the high end travel. I need a tach and volt meter on the cluster, I have seen a few I like but, dont know if our truck is a single ignition pack or dual or what i need exactly.

I love this forum and the help. Thank you gents.

 

[DLJIII]

Ryan, is this what you are talking about?

http://www.ebay.com/itm/like/122262064649?lpid=82&chn=ps&ul_noapp=true

12 & 24v alternator and its only three bills.

 

[Wire Fox]

Ok, I tested the charge voltage. Idle sits about 23.6 to 24.4 volts, when the engine kicks in and hits the generator the voltage spikes to 30.4-32.8 volts for any time between five seconds to 25 seconds.

The two batteries are dated 05-16 so they are newer than I expected.

My insurance company told me to come back later when they figure out how to insure it and in order to get a title transfer I need insurance so right now I am waiting but, not worried.

I will look into the replacement alternator tonight after work and I was hoping someone could shine some light on the rear wheel noise.
A chunking, thumping, flat tire sound at a low rate or speed and during turns or shifts in weight you can hear it vibrate.
What are the possibilities and how much can I expect to spend fixing a barring or U joint or what may be the cause?

Thank ya. I love my truck by the way, I am normally a speeder but, I certainly dont mind cruising a whole 47 mph. It feels very optimal for the truck for the high end travel. I need a tach and volt meter on the cluster, I have seen a few I like but, dont know if our truck is a single ignition pack or dual or what i need exactly.

I love this forum and the help. Thank you gents.

Your voltage is definitely not regulated properly...I wouldn't run it until you get that fixed. At the least, it's the regulator. At the worst, it's the alternator itself. Sounds like you've already got one on the way to replace it all.

Your wheels are not driven by U-joints; your wheels use CV axles. (the propeller shafts from transfer case to differentials DO have u-joints) You're going to need to generally inspect the rear suspension and look for loose or broken components. Ball joints, control arms, CV axle bolts, brake calipers, spindle nut, shocks, etc. The TM can guide you on what to inspect and how to inspect it. If you're not comfortable with doing the job yourself, I'd have a mechanic look it over or find a nearby SS member that would be willing to look it over for you and offer some guidance to you for lunch and a six pack. Be warned that your average mechanic will not know how to work with the geared hub assembly. The cost of the repair can be $5 for some thread sealant on up to a few hundred dollars for replacing a damaged control arm.

 

[snowtrac nome]

I would look at the 6 bolts holding the axleshafts to the differential. I have seen these come loose may also be part of the brake problem as they also hold the rotors on.

 

[DLJIII]

Ok, thank you so much Wire. I am totally new to this vehicle and everything.
I watched a couple of videos on youtube of changing rear end components and it looks straight forward enough.
I have no idea what the TM is or where to find it, I bet its a tech manual and is in the resources section.
Ok, I will check the bolts and give it a once over tomorrow before work.
I am dying to crack into this beast but, work gets in the way haha.
Thank you guys for the help.
I will keep the thread updated as things progress.

 

[Action]

TM 9-2320-280-10
Operator's Manual