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If you would like to get a little experience with these trucks, I have a few and you're welcome to stop by and check them out. I have nothing to sell, so there's no pressure. Then when it's time to buy, you have a better idea of what you're getting into, and what to look out for.

Big Tex - If your motor is running properly, with correct fuel delivery, the pump adjustments listed in this thread will make a big improvement. My 923A2 has the full rack travel turned all the way out, and a few turns of pre-boost fuel added as well. The truck moves pretty well, and not...

Your T-stat is opening (at least part way), as the fan shutter-stat is reaching 180 and running the fan. Is the radiator getting hot also? Hot inlet at top and cold outlet at bottom of the radiator could mean minimal coolant flow. Is the coolant system building pressure before it reaches temp?

Crew cab builders- Have any of you considered a soft top for your truck? I'm thinking about biulding an extended cab w/o rear doors, or a "shorter" crew cab with less room in the rear seat row. The builds I have read about all have hard tops, and I'd like to try one with an easily removable...

The pressue limit is for the 2 piece rim, not the tire. They're stamped 85 psi max.

I attempted riding around with lots of weight (8k or so in the bed),varying tire pressure for many miles and the tires never improved. The trucks do ride better with weight added though. Wearing the tire down with road use will also not improve any distortion or run-out. If you try it, you...

Here's a few pics of the tire shaving process. Keep in mind this could make the weight balance worse if an uneven amount of material was removed. I had already added Counteract balance beads. As for tire pressure, the AT2A's are rated for 9900lbs at 100psi. Our trucks empty don't weigh very...

I had a shop shave the tires. The procedure was performed with the tires on the truck. It took about half a day, im thinking I paid around $40 per tire. I'll post a pic later.

Get them shaved! I tried balancing, etc with no improvement. Shaving, buffing, grinding the tires is the only thing that corrected the shake on my truck. I ran almost 1000 miles at varying air pressures hoping to wear the tires even, but only shaving corrected the problem. Even a tire which...

Bringing this back up, as by now there is likely more of these trucks in commercial service. Has anyone gone through a roadside inspection with an M939 truck yet? DOT / motor carrier enforcement is becomming more common with local LEO around here, as an easy way to generate revenue, and...

You will find that the truck is not real enjoyable to drive at 65 mph, even if you had an OD. I'm considering a Fuller manual transmission swap at some point, but there's really no way to justify it, other than improving the truck's on-road drivability. For off-road, the Allison seems to be a...

Tashaak- To clairify, the length above does NOT include the Tee handle. Sorry, didn't get you a photo (phone trouble).

Dipstick length top cover to bottom: 17" Cold full mark to bottom 2 1/4" Add mark to bottom: 3 1/2" Full mark to bottom: 4 1/2" This is for one of my A2 trucks with the 6cta

I'm hoping the prices stay high for a few reasons. 1. It's easier for me to justify spending money maintaining, and upgrading a truck worth 8,000 than one worth 2,000. 2. If I find the right classic Mack, my 5-tonners have to go. I'd rather sell in a strong market.

Keep in mind the m939 trucks are NOT ABS on the steer axle. They are equipped with a ratio valve which reduces applied air pressure to the steers, unless you really mash the pedal. Another quick and dirty way to check your ABS - Turn the engine switch from OFF to ON and listen for two sets of...

Make sure the handle for your trolley brakes is released completely. Same thing occurred on my 931A2.

FFR Cobra- Your air pressure drop is due to the volume of air required to apply all of the brakes hard. If it held steady after the initial drop, you are likely OK

Kentucky - what motor are you working on? Your IP should be under positive pressure at the inlet, so any leaks would let fuel escape as opposed to letting air into the system. Is there a way you can put the clear line at the suction end of your electric pump.

This is the tire buffing / shaving process I mentioned a few posts back. It removes material to eliminate high spots until the tire is in round. I had already tried balancing beads, air pressure adjustments etc. 95% of the shake is gone, and my truck was really bad when the out of round tires...

You likely have one or more tires out of round. My truck felt like it had Fred Flinstone tires until I had them buffed/ shaved to bring them in true. I lost a good bit of tread in the process but it was worth it.