oilburner

The 15 speed and a 300 Mack with a 4.44 ratio I drove would pull right with a 425 cat. It could hav been a 350 that's what the owner of the truck said it was but it looked like a 300 it had that tip turbine on it. It was a good set up

I have never seen a one stick 12 speed how did that work, I had a guy tell me he had a 12 speed in a r model once but it was a one stick 10 speed that shifted like a super ten. If you like a deep reduction and a close ratio with a overdrive I would go with a 15 speed fuller.

this is a 8ll and a Mack 8 speed

Is it 1,2,3, in low then 1,2,3,4,5 in direct that's how the 8 speed Mack that I have seen shift

That is a good looking old super dog. I would really like to own but a long way from old Kentucky. It having a non Mack drivetrain will turn a lot of Mack guys off but they just don't understand the old big cam cummins. By looking at the pics the engine looks like one of the better cummins at least a big cam 3 and may be a 4 it had the holset turbo and pulse manifold so this one will whistle when you get her in a pull lot better then what the truck came out with in 80 the old 290 were good engine but they could have used a little more power or at least torque. If that truck was for sale close like the rest of the guys said I would get her. And if it were mine it would cost a lot more than what your asking you just can't find these old trucks in that kind of shape and anything that needs to be done to them you can do your self. This truck would be a great owner operators first truck and with the cummins all I would do is slap a jake on it and roll. Good luck

Ok now I have done it again. You all ready have the big overdrive. For some reason I thought you had a 10 speed. Yea your as fast as you can go unless you stuck a brownie box in the middle.

My truck has a 5.13 ratio and a 107x six speed and 24.5 tall rubber and it will do 56 mph at 2100. Now if I had a .60 overdrive that would give me 40 percent more speed so I would be at about 20 more mph on top. So if he had let's say a 7 or 8 speed with the big overdrive even if he had a .71 over now he would gain 5 or 6 more mph on the top end

Well looks like I stuck my foot in my mouth. Looked at the ratio charts and David you are right. It is a .71.

You may be right David but I am pretty sure the Mack nine speed is a .60 at least I thank they made one like that. A guy I run with had a old dm with a six speed in it and it would do about 62 mph. He swap out the six speed with a Mack nine and it would do 80 mph with the nine speed. And it still had a pretty good low hole for pulling out loaded

Well looks like I should have read all the post. The engine is already apart. Let us know how it ends up

If you let it set and idle does it start hazeing blue smoke that will burn your eyes.

That is a good looking dm.

I am not sure what overdrive you have but Mack makes a nine speed that had a .60 overdrive. With tall 24.5 rubber and a 505 ratio and 2100 rpm that would be close to 80 mph maybe 78 or so

I drove one once that done the same thing but if you did not pre select it pull it out of gear then put it in high range it would not grind. I like the nine speed Mack. It has a good low and a overdrive that will put you in the clouds.

You might go with a Mack nine speed. I maybe wrong but they are a .60 overdrive and they have a good low hole. If you have enough motor to pull out the big jumps in the ratio of the trans