I considering buying a mid 70's Mack R that has a 5 speed in it. It only has a top speed of 55mph but it pulls 80k with no sweat. Is there any transmission that I could stick in it to get at least 65mph out of it without running the engine on the governor all day? Will I have to fabricate anything to get an eaton or something in it or will it bolt up? I'm not familiar with big trucks so help me out. Thanks

 

brownie box. look em up.

 

^ As stated above, you can throw a Brownlite behind the five speed but you need to be careful. If the truck is a Maxidyne you will need the trans. that is in it now. You would be better off changing the rear but if it's a screw it will get pricey.

 

Why does the the maxidyne need that transmission behind it? I'm not familiar with these old trucks.

 

I put a brownie behind a f600 gasser. 3sp one over, direct,one under, it changed that truck 100%. It took a worthless pos and transformed it into a sweet ride! Enjoy learning to shift the twin sticks!

 

The Maxidyn was one of, if not the first high torgue rise engine. The thing was awsome! Just when you thought you were going to have to downshift, the engine would just begin to pull real hard, the turbo would whine and there you went.

You could spot one from a distance because a regular Mack bulldog was silver, a dyn was gold.