GearheadGrrrl

The MR tandem tractors ride is acceptable, but not as smooth as a CH or Vision. The single axle is another matter, and several Postal Service drivers have suffered neck and back injuries driving them. The tandem is a great truck for urban trucking though- the 135 inch wheelbase, low cab height, and automatic transmission almost make city driving enjoyable. I think part of the slow sales of these tractors is the Postal Service's decision to send them to a dealer only auction. Previously they would park them in front of the garage office with a sign stating there condition and price. Anyone and everyone could and did buy them, and if they didn't sell the price was dropped until they did. I suspect the dealers sales lots are already pretty full and their not about to bid on a cabover that might bring only $5000 gross.

Well, our new Visions have arrived, and some of the old MRs have gone off to the auction... But I've seen only 2 of these hundreds of tractors offered for sale. Both are 1997 MR688STs with between 200,000-300,000 miles with automatics. One has been listed in Truck Paper for weeks, asking $15,000. The other just turned up on eBay, and with an hour left looks like it'll be lucky to draw a $5000 bid. This has me wondering- perhaps the MR tractors are so undersirable that no one has bid on them at the dealer only auctions they were sent too? Perhaps the dealers on this board can shed some light here- I'm in the market for one of these tractors, and if they're going for $5000 or less I may buy more than one!

What you're looking at is a parts truck- blown engine, some parts stripped already, etc.. It's never worth it to ship a parts truck clear across the country- for what you'd have in it by the time you get it home you could have a running Superliner.

Yes, but if you give it more air you'll have to give it more fuel too...

I'm not certain that custom was a B model... the lines look a bit like a K model International.

The problem with Hank's truck pictures site is that every time I go there I spend at least half an hour oogling...

The Postal Serviice Macks have the 300 horse E7 with Allison automatic, Eaton rears (power divider guarenteed to blow before 400,000 miles) on Hendrickson air ride, air starter, 60 gallon tank, and no air conditioning or even a radio. The CH613 tractor weights around 16,200 pounds with me and maybe 30 gallons of fuel, so they're under 16,000 pounds empty. The MR613 tractor weights around 17,000 pounds, probably due to the 1/4 inch thick front bumper with a 1/4 inch reinforcement behind it, the deep belly frame, and all the other heavy duty stuf that makes an MR an MR.

That's a respectable weight- some of the newer tractors weigh close to 20,000 pounds fueled up and ready for the road. A Postal Service CH613 tractor with that much fuel and no wet kit, toolbox, etc. weights a bit over 16,000 pounds for comparison.

It sits kind of abnormally low in back too- perhaps some spring leaves and/or spacers have been removed? Then again, maybe it has air ride and it's outa air...

Modblaster, you might want to remember that an MR doesn't have the massive radiator of the conventionals. That may explain why Mack doesn't offer more than 400 horses in the MR, and suggest that you might want to stick to the 400 horse rating. By the way, what transmission does your truck have, and does it have a retarder for getting down the mountain?

At the Postal Service among about 100 CDL drivers at our location were a couple who'd never driven a stick shift- they came to work for the Postal Serrice straight from the military where they drove automatics. Combine that with all the city driving we do and it's no wonder they went to automatics!

A lot of these guys that just quit Swift/ J.B. Hunt/ etc. can't back up worth a damn either!

And going from a .73 to .71 overdrive will give you maybe 2 more MPH.

All the Postal Service's Macks have Allisons and for the city driving we do we love 'em. They easily out accellerate a manual and have left a lot off " Brand x" drivers with 14 liter and bigger engines wondering waht was wrong with their engines. The Allison is damn near unbeakable too- rebuilds are rare, and the only time they break down is when a hose from the Allison to the oil cooler breaks. The mechanics just patch the leak, refill the system, ad she's good as new.

The G model was a much more advanced design also, with a taller windows for better visibility and rounded front corners to reduce wind resistance. If I didn't know when the G was built I would assume it was a 1980s design.

The G model and Cruiseliner look similar- did they reuse some of the G model design and tooling to build the Cruiseliner?

A lot of the air throttles use what looks like a regular brake pedal. They work OK, other than a rough off idle to power transition due to the air system having a crack pressure of 5 psi or so. This was a concern on single axle MRs bobtailing with only 4000 pounds on the rear axle in ice and snow because it set the wheels spinning pulling away from a stop, but with a trailer on it's no problem. As far as not being able to give it some throttle for a cold start when the air tanks were empty... We had air starters so we had to air them up anyways!

Mack installed them on the 1991 MR tractors built for the Postal Service.

There is a demand for 16 liter 600+ horse engines in places like Canada, Michigan, etc.. While the on road haulers in those states may find happiness with a Volvo with their 16 liter motor, the loggers and other on/off road haulers need the Mack drivetrain and chassis features that Volvo doesn't offer. Mack had thusly better get a Volvo 16 liter motor under a Mack hood ASAP!

Round tanks were pretty common on R models by 1980, but I remember some of the big fleets stuck with square tanks well into the 1980s.

I drove a 1970 vintage R model tandem at Dakota County Vo-Tech back in '77 that had Mack rears with no power divider on camelback suspension. Mack claims that the camelback flexes like railroad car trucks, bringing the inside wheels closer together and spreading the outside wheels as the spring compresses from the swaying load. Thusly the inside and ouside wheels turn at about the same spped and reputedly no interaxle differential is needed. When Mack started offering their tandems on other's suspensions they had to develop an interaxle differentilal, and the overrunning pawl design they use is a most elegant one. I drove a 1970 vintage R model tandem at Dakota County Vo-Tech back in '77 that had Mack rears with no power divider on camelback suspension. Mack claims that the camelback flexes like railroad car trucks, bringing the inside wheels closer together and spreading the outside wheels as the spring compresses from the swaying load. Thusly the inside and ouside wheels turn at about the same spped and reputedly no interaxle differential is needed. When Mack started offering their tandems on other's suspensions they had to develop an interaxle differentilal, and the overrunning pawl design they use is a most elegant one.

The Scania engines have an excellent reputation in Europe and typically have a million mile life to rebuild. There's a guy in Southern Minnesota who bought one new years ago, last I saw him he had 1,400,000 miles on it without an engine rebuild, thought he rebuilt the synchronized transmission at about 800,000 miles.

I concur on the maneuverability concerns- the Minneapolis Main Post Office where I used to run the spotting tractor has an indoor loading dock designed for a 45' trailer and a non sleeper tractor. It's tolerable with a 175" wheelbase CH and a 48' trailer, but the guys who come in with the large cars and 53' trailers often spend 15 minutes backing in. The CH or Vision with a small sleeper or similar Volvo integral sleeper usually only need 5 minutes. The Post Office drivers with a MR cabover (110" or 135" wheelbase) generally get backed in first try in less than a minute. Of I were buying a new Mack tractor to pull a dump trailer it'd be a Granite with Maxidyne/Maxitorque combo driving Mack rears on air ride...

Mack hasn't built a hyper long hood truck because the Mack engine is compact and will fit under a normal length hood.

$400 for a new Eaton 'box is a bargain thought- I grind a few more gears for that kind of savings!