M-Drive

[Jeffrey Baker]

The only thing that I have had issue with my m-drive is the programing needed to be tweaked. I am running two and will receive a third in a few weeks. The two trucks had different programing (might have been a bit of hte learning the transmission does) the one you had to pretty much stomp on the break in order for it do downshift. A quick reprogramming and it seemed to fix the issue.

Based on your avatar it looks like you work for Trimac. Around here they seem to be the last fuel hauler to pick up Macks but saw one sitting at the dealership ready to be taken home last night.

[lucerne tractor]

Pretty impessive move with automatics.

[REOGasMackDiesel]

I like manual transmissions better myself

Mike

[LSI]

Direct top gear has more rwhp and tq the higher the top gear ratio in the trans the lower the torque multiplication. I would build one with a direct top gear 10 spd, MP8 505, and somewhere in the 2.50-2.70 rears. I would be looking for a cruising rpm of about 1400, if you have that kind of engine HP and tq and a direct trans you should get great MPG. I have asked why the Super Econodyne has an OD top gear trans and was told it was because they didn't have a direct. Take two identical trucks same engine same body/frame/weight, put an OD and 3:42 gears in one and a direct and 2:60 gears in the other. The direct truck will pull better and get better MPG because its not turning the drive shaft faster than the input which adds a lot of resistance thus making less rwhp/tq. Make sense? Turn your trans output shaft the same speed as the input or 1:1 direct you make more rwhp/tq, try it in the truck you have now. Take your truck out on the road with an OD trans and run it for a while in direct in most 9/10spds that's one gear down in a 13/18 its one whole gear down in high, keep the rpm down to about 14-1450 I bet it pulls better than in OD at that rpm. Of course at higher speeds you get more aerodynamic drag and rolling resistance but you'll get the basic idea. If you have a hill you go over often that drags you down go ahead and slow down before you start up it and go into direct in most cases you'll pull it out or wait much longer to drop a gear due to the higher rwhp/tq. Oh and for mileage id go with low pro 24.5 tires, 22.5's are great and 11R22.5's s are the same diameter, however the taller the sidewall the more rolling resistance so shorter sidewalls equal better MPG. The short sidewall concept works with low pro 22.5's too but also consider the friction of the differentials,axles and wheel bearings, with taller tires the axles turn slower creating less friction thus more MPG. Ok that's all for tonight I'm out.

Talked to a fleet in Iowa running mp8, 455hp,1760ftlb, M-drive direct,2:69 rears,S40's twin y and they are in the uper 7's.

Mack has a 2:49.Wonder how that would work?Sharkey is running mp7's, 1650ftlb,400hp, with m-drive O.D. and 3:32's and getting 6.8 which doesn't look that good to me.When you under power your fuel goes down as well as power.

Edited April 27, 2013 by LSI

[rsb502]

Yeah you gotta have enough power that the trucks not always running wide open to maintain speed. I would go for an MP8 with as much HP as I could get then it can just lug along, you can look in the ecm of a truck and see how much time is spent at 100% power and with a smaller engine its way up there, larger engine and or higher HP its about half we proved the concept at Howard Baer with two identical Freightliners with N14s we set one at 435 and the other at 525, the 525 got 1.6mpg better over 3 months and the % of time at 100% throttle was half the 435.