I was wondering if anyone knows what transmission they put in these busses? It has a 5.9 cummins with a six speed tranny but with the way it is set up it has a max speed of 58mph. Ratio of the rear end? I was looking to get a lot more out of it. The other problem is it doesn't have a tach so I don't know the rpms at top speed to see if there is more in the engine or defueling early? Thanks.

 

The defuel early in the MD trucks. It's probably only hitting 2500rpm when you hit 58mph. There should be an ID on the side of the trans. Sounds like it's non-overdrive, and you got 4.78-5.29-ish rear gears(depending on tire size). going with an OD trans or a re-gear would drop the rpm to something more reasonable. You can buy an aftermarket tach to work with it, one that goes off the flywheel.

 

I recently bought a 94 F-700 with a 5.9L Cummins and a 6 speed trans.
Look at your trans case on the passenger side for the id plate.
Mine has on it Eaton model #FS-5106A (mine is NOT an overdrive)
If yours has that here you go:
From the eaton website for a FS-5106A trans.
1st 9.01
2nd 5.27
3rd 3.25
4th 2.04
5th 1.36
6th 1.00
rev 8.63
Weight 362 lbs
Hold about 9 quarts of lube.


Mine also has 5.29 gears and 11R22.5 tires Slightly over 41 inches tall.
And according to the speedo does about 64 at 2850 or so max.

Here is a formula for figuring RPM at a given speed with out overdive.

MPH X GEAR X 336 / Overall tire height in inches = RPM

Example
60 X 5.29 X 336/ 41.3 = 2582 RPM

If you have a large eaton rear axle look at the top of the center chunk for the ratio to be stenciled into the metal.
On mine in between the 5 and the 2 it has what looks like a star.
as in 5*29