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Shifting a twin stick Mack

T

terex herder

Senior Member
Joined
Nov 10, 2017
Messages
1,804
Location
Kansas
I looking at buying a 1980 Mack dump truck. Its a gold dog truck, and that is about all I know at this point. It has the twin stick transmission, and no shifting pattern on the dash/knobs.

How do these sticks shift?
 
C

check

Senior Member
Joined
Apr 1, 2012
Messages
800
Location
in the mail
I would call it "Main" and "HLR".
Put the main in first and HLR in L. Then shift HLR to H. Then upshift the main like any 5 speed. When you need reverse, put main in first, HLR in R.

Edit: "H" is actually direct. I haven't driven one since 1982. Makes sense that mack would put reverse in the compound box since the main is a triple coutershaft tranny.
 
R

renovator

Well-Known Member
Joined
Oct 27, 2011
Messages
69
Location
New Mexico
It will be nice if it has some sort of engine brake. There is big gap between gears on those Mack 5 speeds, and it seems like it takes forever for the engine speed to drop enough to grab the next gear without something to help. When loaded, it would take so long and so much road speed lost, I would just have to go back to where I was and try again.
 
H

highwayghost

Senior Member
Joined
Nov 1, 2019
Messages
315
Location
Pittsburgh, PA
Occupation
Emissions Analyst
WoW...Been a long time since I drove one of those!!:) I can remember many times having both hands on the two gear shifts to try to get the timing right for shifts. Bring a friend along to help steer! :p
 
H

highwayghost

Senior Member
Joined
Nov 1, 2019
Messages
315
Location
Pittsburgh, PA
Occupation
Emissions Analyst
This one would keep your mind sharp. No driving with a hang over:p



images
 
dieseldog5.9

dieseldog5.9

Senior Member
Joined
Aug 11, 2014
Messages
614
Location
New Hampshire
Drove a 6 speed mack this week, guys around here and massachussets love them, Mack sold that transmission up into the early 2000's, one old timer told me why have all those gears when 6 gets the job done. Those transmissions shine on the jobsite, Low hole, 5 reverse gears, I was told you have to shift them on the Jake to keep from loosing road speed.
 
C

check

Senior Member
Joined
Apr 1, 2012
Messages
800
Location
in the mail
Our fleet didn't have them, but Macks back then had something called a "Dynatard Cam" as their Jake brake. If you ever adjust valve lash on them, make sure you do it like the manual says, using crankshaft positions on front pulley.
 
Steve Frazier

Steve Frazier

Founder
Staff member
Joined
Oct 30, 2003
Messages
6,609
Location
LaGrangeville, N.Y.
I drove a DM600 for a paving company with this transmission. Like the others have mentioned it's basically like driving a straight 5 speed transmission with a low range for off road. On steep hills you can get gear bound but on moderate inclines the torque of the old Mack will tug you along. The one I drove had a Mack Dynatard engine brake which help with quick shifting when necessary. There are 5 speeds in reverse and you can back up at close to 30mph, came in handy when you had to back in to the paver almost a mile.
 
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