Mack MR concrete truck?

[JoeH]

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.

[1965]

The true automatic (Allison)  in dump trucks around here will out perform any standard. They’ll go places offsite that standard want try. There quicker off red lights too.

[JoeH]

10 hours ago, 1965 said:

The true automatic (Allison)  in dump trucks around here will out perform any standard. They’ll go places offsite that standard want try. There quicker off red lights too.

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

[1965]

These dump trucks are newer trucks. The newer stuff is electronic. You didn’t see many in older trucks because of the $$$ & people knew how to drive standard shift. Those older (750 I believe) were in them back when I worked for DD & Allison dealer. They were in buses & fire trucks. Saw 1 in a peterbuilt for heavy haul truck that was high hp. They would do the job. You just need to drive 1. They have retarders & all back then too.

[JoeH]

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?

[1965]

I haven’t driven 1 myself so I can’t honestly answer that, but I know garbage trucks has run them along time running in out of landfills. I’ve never heard that the converter wasn’t locked up in low gear, that seems hard to believe.