Victoria - 1989 DM686

[89DM686]

Well, I'm not entirely sure whether to post my latest acquisiion in the antique or modern subforum, as she kind of sits in between being a genuine classic (70s and earlier) and modern.

 

So, if the moderators see a need to shift my topic to another subforum please do.

 

Vicky is a 1989 DM686, ex-mixer chassis that I bought as of last week, clean title, running and driving (if a tad low on air pressure in the tires). I bought the Mack for the purpose of building a heavy spec local 4-axle tractor.

 

I run heavy haul through the hot months, largely within about 150 miles of Denver. We do a lot of jobsite to jobsite work, rather than dealer to dealer or manufacturer to dealer work.

 

My primary tractor is Suzie-Q, a 1990 W900B Kenworth with a 444 Cummins and factory 6x4 set of boxes. I love her to death, she's been an absolute sweetheart to me. She's grossed over 200,000lbs, and does it without question. She's got DS402 4.44 cogs out back, dragging weight isn't an issue.

 

That being said, Colorado allows pretty aggressive axle weights, and we get into some specialized work requiring high frame load on the power unit. I've pushed the DS Eatons as heavy as 62,000lbs (no lift or jeep) under limited circumstances, but, at this point I'd like to have a heavy spec for that sort of thing locally, while Suzie can run the big stuff when we get the 2-2-2 or 2-3-2 out to spread weight.

 

Vicky has a 20,000 steer and 54,000lb Mack rears on walking beam "suspension", a rather euphemistic way to describe Mack's walking beam suspension.

 

She's short, too. All of a 190in wheelbase.

 

I'm intending the strip the rest of the mixer gear and slip a 20,000lb lift under her, giving her a 94,000lb GVWR. With a four axle tractor, maximum legal load on the tractor is 90,000lbs with an annual oversize (20k on steer, 70k on three axle drive grouping). Sitting pretty on that one. Assuredly, some site or off-road moves we'll be throwing the axle weight limitations out the door, as well.

 

Vicky has a 1071A Mack 6spd. One of the things I was happiest about this truck having, as it gives me the nearly absurd 23:1 low hole.

 

I'm considering dropping a 1241D behind the 1071A, however. The truck does have the high torque rise E6 in it, however, I'm thinking, in mountain situations, when needing pull heavy grades, some ability to split the 6spd might be useful to me. Honestly, the 1241D would largely be used as a 3spd, primarily splitting between under and direct, and then gaining the OD gear for empty running in the auxiliary.

 

I'm wondering if anyone here has experience with adding an auxiliary behind a 6spd or 5spd Mack and if they feel the addition was worthwhile.

 

I don't want to swap to a different main, so to speak. The 23:1 low is ideal for extrmely heavy starts.

 

Other plans include Cozad ramps and pintle hitch out back, headache rack. She'll get some chrome, but not much. She'll be kept in form to do dirty work in nasty conditions. A single, short stack, chrome cap, polished tanks and diamond plate fenders are about the sum total of planned shiny things.

 

If you happen to know DM's well, feel free to add whatever knowledge you have. I bought the truck knowing the older mechanical Mack's tended to have bulletproof components, precisely what I want when I'm going to shove 45 tons onto the power unit. But, I can't say I know a great level of detail about Mack components. So, teach me what you know.

 

Troy.

[89DM686]

A few more pics...

[gxbxc]

looks kinda nice but mixers have a lot of rust because they clean then with acid and if the driver is lazy it didn't get rinsed good ,so take a good hard look at the double frame

[89DM686]

I've looked over for rust issues thoroughly. Luckily, as a western truck (it operated out of Baggs, Wyoming when it was a mixer) the truck lived in a much drier climate than a lot of Mack's out East do. I've found some surface rust areas around the cab, but, nothing cancerous.

The most important aspect, the frame, is very clean. No decades old concrete stuck on or heavy rust. The cab and hood have a couple rough spots, nothing unfixable though. The main center bushing for the walking beam appears to be in good knick, the control arms will need rebushed, but that's a pretty minor job.

 

Interior wise the seat is a little rough, but a peak behind the dash shows good, if dusty, wiring.

Edited July 1, 2018 by 89DM686

[blackdog2]

I just bought this DM-686sx 58,000 lbs rears 130,000 miles .trailer 22ft air ride all alum frame tub

[mowerman]

Interesting story best of luck I would swap the transmission bob


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[terry]

That DM with them drive train components are a trouble free set up! Do you know what that walking beam set up is rated for, I think I have seen a heavier beam on some models with the bronze trunnion bushing.    terry

[mackey58]

That DM combo is Sweet!!!!

[Jamaican Bulldog]

Glad to see a DM tractor. So rare to see and my favorite Mack.

[gxbxc]

Black dog where did the hard nose DM come from, use to see a lot like it when I lived in Ct, and it is one nice looking truck

[j hancock]

Victoria looks great!  

I think having the aux, trans will be a benefit for the type of work you are doing.  The Maxidyne has a wide power band allowing the use of 5 or 6 spd transmissions but that was based more on normal road use and 80K gvw.  Your work is not typical and is certainly above 80K.  Being able to split a gear based on weight and grade adds flexibility. 

[blackdog2]

17 hours ago, gxbxc said:

Black dog where did the hard nose DM come from, use to see a lot like it when I lived in Ct, and it is one nice looking truck

It was a tri-axle then a crash truck then the guy I bought it from turned it to a tractor changing the rears ratio does 71-mph F.P. RYAN aka Defelice the body went up hitting a bridge bending frame and hitting cab a couple months old  new cab level 3 dual air seats A/C .

[89DM686]

7 hours ago, j hancock said:

Victoria looks great!  

I think having the aux, trans will be a benefit for the type of work you are doing.  The Maxidyne has a wide power band allowing the use of 5 or 6 spd transmissions but that was based more on normal road use and 80K gvw.  Your work is not typical and is certainly above 80K.  Being able to split a gear based on weight and grade adds flexibility. 

 thats my thinking. Truck will see upwards of 250,000lbs gross, so, thinking the wide torque band will be insufficient on gradeability. Don't need a C box, Maxitorque already offers plenty of reduction as is, but, being able to have some reasonable splits will probably help, and gaining an OD gear for empty running coming home. I think a 1241D would be fairly ideal splitting between under and direct and then having OD for coming home. Don't think a single countershaft 3spd would survive torque multiplication coming out of the Maxitorque in underdriven gears, and one of the big 2spd Eaton aux's weren't designed to shift on the fly.

Edited July 2, 2018 by 89DM686

[blackdog2]

side shot

[terry]

Very, very nice!! Bet she is a rough ride with that short wheelbase and rear suspension, but I still love it!!    terry👍

[blackdog2]

believe it rides nice

[mackey58]

Awwww man those girls are nice

[david wild]

Cozad ramps ? your talking west coast to most people now. very few people on the east coast know what Cozad ramps are, your 4 speed aux. should work fine, little Mack engine won't make enough power to hurt it, anything bigger and you'll being putting new bearings in it constantly, AT1202 is what most heavy trucks use, there is a new 3 speed out that is supposed to be great but when I looked at the price I went back to the AT1202.  Nice looking trucks.