JoeH

Today's progress: right frame rail installed, tandem slid forward to the new wheelbase. Miscellaneous brackets installed for bumper, skid plate, cab tilt, exhaust, fuel tank, etc. Shortened driveshaft should arrive tomorrow or Friday, hopefully the lift axle is coming by Friday, though the tracking number TForce Freight provides is bogus. All in all I think we've made a lot of progress in 2 weeks. Won't be particularly pretty when it's done, but we've always had more interest in structural integrity than chrome. These trucks just get covered in concrete dust. All this work is simply to eliminate the Rust Jacking in the frame, not to make it cute.

Sleeper would be interested on an MR, it couldn't mate to the cab as there's part of an engine in the way. Would definitely be a neat rig if you could pull it off!

New Years Eve had the paint store closed, so we didn't get as much done last Friday as we hoped. Finally got the right frame rails and about 10-15 miscellaneous brackets sand blasted and painted. Everything is sitting in the garage baking at 75 degrees overnight. 8am tomorrow starts the install process. Should go smoothly, no reason for it not to. Lift axle should arrive end of the week, hopefully the shortened driveshaft will be back soon too. One of my tenants is a collision center, I may ask them to prep the cab for paint. That's one task I don't enjoy so much. More pictures promised as progress continues!

I think this hits closer to the mark. "Lugging" is trying to accelerate when you are too far below your power band. There is a surging effect in power delivery that damages things. Mack figured out how to make smooth power at a lower RPM, allowing them to start the power band lower and thus reduce the need for so many gears. All this achieved by injection timing, fuel delivery, etc. Mack, having engineering control over every vehicle component from engine to trans to rears allowed them to do what other brands like CAT and Cummins couldn't. CAT and Cummins had to design their power delivery to match generic transmissions. Not a chance in hell Eaton would have made a 5-6 speed transmission to pair as an option for one specific CAT motor with a wide power band motor. Not enough sales market. Eaton would be dependent on the end user spec'ing a KW or Pete with that motor and trans to sell the transmission. Mack was able to build a 40+ year reputation on it. I don't know what kind of market share Mack had on OTR long haul trucking from the 60s to 2000, but I'm guessing not too much as truck stops don't seem to favor them. I'd guess the Maxidyne setup earned them a huge share of local/regional market, where 55-60mph was all that was ever asked of a truck, but left the market open to CAT and Cummins for cross country trucking where the bigger liter engines moved along at 70+ mph.

Type of valves shouldn't matter, the slower an engine turns over the easier it is to keep valve train (pushrods, rockets, lifters, etc.) from floating. Do t know what Rees valves are.

My understanding is that it is high oil pressure. Most trucks regulate oil pressure around 45 psi, but our 1979 maxidyne runs about 90 psi. The higher your oil pressure the more it can withstand the downward pressures in the crankshaft journals before metal to metal contact.

Yes there is a wagon hiding in that last picture. While most people set old wagons in their front yard to rot away we prefer to keep our 150 year old (rough estimate) wagon up high and dry in our garage.last time it came out was for Chalfont, PA's bicentennial parade in I believe 2002 or 2004. Next time it comes out will probably be my 4 year old daughter's wedding in 20 years.

Right frame rail has the cab tilt mechanism, and since the right frame rail isn't in the truck right now..... We had to improvise. Left rail cab hinge is installed, right cab hinge is suspended by strap, and the cab gutter line is suspended from another strap, from beams going from our A frame to our pallet shelving. Redneck ingenuity is heavily at work here...

Left rail is primered painted and installed. Right rail has been removed and separated, tomorrow is hopefully sandblast, primer, paint. Supply chain issues are a bit screwy. In our hurry to get going we have had to reuse a lot of bolts before sourcing new ones. Last truck we did like this was 10 years ago, and I dont think we had any trouble getting bolts. Pictures show left rails laying flat vs right rails still with rust jacking.

An interesting proposition, perhaps a project for down the road. Budget and time don't allow for it now, truck needs to be in Iowa in February to get the body mounted on.

I think I will too, I've driven automatic oil/propane delivery trucks and they're easy. What I'm nervous about is off-road capabilities. We get in people's back yards and find soft ground sometimes. I need to inspect the automatic power divider. Full lockers would be sweet but they're hard to come by. Truck has Automatic Traction Control, piggy backed into the ABS system, which I had hoped was on all 4 drives wheels, but it's only on steer and rear drive axle. I may buy toner ring hubs for the intermediate axle and steal the steering ABS sensor system for the intermediate axle so I have traction control on 4 drives.

In my lifetime to date, (I'm 32) we (I'm 3rd generation) have only had R models and a DM. This is our first MR cab, and so far this has been a dream to work on. All the cab electricals are under a massive plate in the middle of the cab that completely comes out to give access to everything. Terminal blocks, circuit breakers, dash switches, etc. 6 screws and you're into everything. The cab tilts forward and you can get to everything on the engine. You can get to the front of the engine, the back of the engine, both sides... Truly the easiest truck I've ever had to work on. Our DM is easily the worst I've ever worked on, you can barely even get to the sides of the engine. We have yet to drive this truck on the road, I'm hoping it will be a relatively smooth ride, but I'm expecting it to be a bit rough. I may wind up only buying MR's from here on out, these things are that nice. I'm sure there's very few MR fans on here, but no one will argue that these trucks are built with the same great reputation we all know Mack had. The R model will always hold a place in my heart, but the MR is moving in next to it! The mixer body going on requires 168 inches from "back of cab" to center of tandem, which on a traditional cab would be far too long for the type of maneuvering we have to do every day. Thus in keeping with traditional Mack philosophy: Out with driver comforts, In with functionality! Merry Christmas!

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?