JoeH

Currently the left frame rail is out & sperated. So much work just to alleviate less than 1/4 inch of rust jacking. Monday will be sandblast the frame in the rain. Will tent it with the boom of our crane and a 30x50 tarp, then run it inside the garage for paint. Then crank up the heat and cook the paint!

So we bought a 2003 MR688S, and are prepping it for a brand new CemenTech volumetric concrete mixer. Have about a month to complete the following: Pull frame rails, separate, sandblast and paint. Reassemble. (One side at a time.) Shorten wheelbase by approximately 16.5 inches. (Slide tandem forward, shorten driveshaft, possible relocate crossmembers) Add 20k lb lift axle. Truck was a tandem axle trash truck, 20k front axle, 44k rear tandem. Replace driver door shell (fiberglass PoS cost $2,000) Paint cab. Trying to figure out how to post pictures.

A 315 is much more forgiving when run with a flat tire next to it, especially with the constant sharp turning. Also has a lot more ground contact when driving into landfills. And yes this was a trash truck. The main question I had on peanuts is whether "full open" was an option, I have to test it again but I think I got it stuck in the yard with only one wheel spinning. I'd love to have full lockers, but people dont spec them enough for there to be any in used parts yards.

Did you put the drums back on?

2003 MR688S, AI-350, Allison HD4560P, 5.32 rears on 315/80R22.5 Top speed? Also, I know Mack makes an air operated and an automatic peanut style power divider. Is there a full open rear tandem setup also? Picture attached.

For $117 it better change itself!

Buying our first computerized truck, a 2003 MR688 with an AI350. What do you guys use for diagnostic adapter and software? I downloaded Diesel Laptop's "Diesel Explorer 2.0". Should I get their adapter or the NexIQ? (The current NexIQ skips out on one of the adapter plugs, while the Diesel Link has all of them. ) I plan on doing the "dead dog" backpressure remediation on this truck at some point, cam, exhaust manifold & pipe, etc.

Buying a 2003 MR688 with an AI350 and an Allison auto. What are my options on engine brakes? Can't find Mack on PacBrake website, an exhaust pipe brake is by far easiest to install.

How many miles/hours? Head gasket could be blown or cylinder sleeves could be pitted enough from cavitation (if they're wet sleeves, not dry) to bleed combustion air into the coolant system. Either scenario puts air into the coolant, which pushes coolant out the overflow discharge hose. Or you have EGR issues.

Our old trucks work every day, we put Mack dealer parts in them, but some guys like PAI aftermarket Mack parts. Haven't tried them myself. We have a '70 2 valve that dropped a valve once. We got away with one head and one cylinder/liner kit.

I suspect we'll never hear from you again....

Looking at buying a used mr688/690 in the 2001-2003 year range. Allison auto 4560. Application will be a volumetric concrete mixer, about a 15 mile radius from our yard. What should I be looking for? One I'm looking at has 484,000 miles, 19,000 hours. What's the life expectancy on EUP alignment dowels?

Picture? And help with what?

I had a blowout on a rear drive tire last week I couldn't drive on as the alligator was still half attached. Was flapping around doing damage to the back of my truck body. Had to have a pair of tires brought to me from the shop. Way easier to tighten 6 spoke lugnuts than 10 Budd lugnuts with a cross wrench.

To answer my own question, here's dimensions of the MRU cab on top, and LEU on the bottom.

does this picture exist for the MR600 series?

Looking for dimensional drawings for Mack MR600 series cab/chassis. Cab/axle, wheelbase, etc. Ultimately looking for a mid 90's to 2001 triaxle MR with a cab/axle of 168", but don't know what that will translate to in wheelbase because I can't find drawings!

VIN will tell you real easily, assuming it has original engine. Dm685xxxxxx is an endt685, dm686xxxxxx is an endt676. Former is the 237, latter is the 283hp motor.

Probably ENDT675

Are you flipping the headlight switch on the dash up or down? Up is headlights, down is clearance lights, middle is off. The switch up on the left of the dash is a high beam momentary switch. It doesn't activate low beams. If you're flipping your switches properly then start with putting new bulbs in and checking the wiring as mentioned above. You can lose a low beam filament without losing the high beam filament in a bulb.

I've driven oil and propane single axle autos, the exhaust brake will throw you through the windshield. The feedback I heard years ago is that they suck off-road, because the torque converter doesn't lock up at low rpm, so you sit there winding up the engine trying to get enough friction built up in the TC to move the truck through soft ground or over obstacles like curbs. The other day on a job I had to back my right drive tires on my triaxle onto 6 inch blocks to keep from tipping over in a soft spot. Do the older autos lend themselves well to this sort of maneuver?

Is that the new stuff or pretty much all Allison's?

Looking into using an MR688 or 690 (mid '90s fully mechanical hopefully) to mount a concrete mixer (volumetric type, not barrel) on. Most are automatic, but the few that I glanced at look like the auto trans has very little ground clearance. Does anyone have any experience with MR's? We hop curbs once in a while, back into people's yards, the usual things Macks are supposed to do. How do the automatics perform in these conditions? Do they have a good torque converter lockup to be able to hop over curbs or soft ground without much fuss? Chances are an auto is a terrible fit for us. Ideally I'll find a gem e7-350 with an 8LL, but I'm curious about the automatics.

Short wheelbase trucks tend to "buck" like a bull rider more noticably, and with how far off the ground you are you feel it more than you would in different wheelbase cars/pickups.

Citing low back pain, get something with light duty springs and a longer wheelbase, plus an air ride cab is a must. Not sure when they started, but Mack offered an option on the R model where the rear cab mount is air bags. Night and day difference on operator back pain. You can convert any truck to single axle air ride, would likely give you a much better ride quality than traditional springs.