Mack transmission and rear axle combinations | TruckersReport.com Trucking Forum

I’m looking at a Mack tri-axle dump truck that I am considering purchasing.

My understanding is that for certain trucks they had rear axles with super low gearing.

But not exactly sure with the ratio is but it’s got to be somewhere between mid-fives up to seven.

These trucks used the T2060 transmission, because it has a .60 Overdrive, and even at that they really only did maybe a little over 60 miles per hour, from what I understand.

Originally the truck had a 300 and it was set up this way. It now has a 350 in it.

My question is, I have a few options with this gearing.

Option 1:
Change the rears to something like a 4.17 or a 4.42.

Is there a way to remove them from under the truck, or do they have to slide out from between the frame rails?

I would be able to use any Fuller transmission.

Option 2:
They apparently installed an 8ll without realizing the rears were geared so low.

This transmission is in good shape.

If I used that transmission, I would need to use some kind of an auxiliary transmission for the additional overdrive needed. I also have a few other Fuller Transmissions, so if I had any problems I have several spares. But they are all .73 overdrive.

Is there an auxiliary transmission that would work with that?

Does an auxiliary transmission make too much rotational drag?

Or, change the rears.

Option 3:

I could just buy a T2060 or 70 or 80 whatever would work better. I believe they all have the same 0.60 overdrive.

That’s probably the most cost effective thing, although I’ve been reading used ones can have a lot of problems, because the drivers seem to want to split all the gears all the time.

Do the 70 or 80 split the gears any better? That’s tough when you have a tall overdrive gear to shift into.

Maybe more gears helps?

Option 4:
I could buy a double overdrive Road Ranger but that would be pricey.

And I believe that’s only .62 Overdrive so it doesn’t really help the top end, but if it were a 13, it would help the splits.

And I already have a really nice heavy duty 13 speed that is like new.

I can put that in my tractor if I don’t use it for this truck.

Anyway I’m sure you guys have seen all of this before, what do you think?