Mack 5speed swap

[Kenny_dodge98]

Whats a better trans to swap in my 90 ch613 has a 300e6 and a 5speed i pull logs so im loaded above 80,000lb every load and having so few gears really kills the truck like it takes me miles to get up to speed. iv found a mack 9 speed from a r model  and a eaton fuller 9 speed from a newer ch that had a e7 motor which would you guys recommended and why and what all do i need for the swap other then trans a air supply for shifter and a drive shaft 

[John Costley]

If your dead set on changing transmissions then I'd look around the bone yards and older rebuilders for an RTOO12513. The brochure page I attached shows the ratios for the RT9513, the RTO9513, and the RTOO9513. the 125 series has the same ratios, they just have a higher torque rating. The OD ratio is only .02 lower than what you have, top speed would barely change.

 

[sllimec47]

Do you run with a dynatard?  I had one installed on my 86 Rd. helped out shifting a lot quicker and made a big difference. 

[OldRedMack]

We did this swap with our 94 300.  We put in a fuller 9L, with the original 5.73 gears it would top out at 62mph at 2100rpm.  We ran it that way for a few years, but we run tandem dumps and max gross in georgia is 64k, so we eventually put 4.64 rears in it.  Turned the pump up a little and she runs like a 350. You need new tranny mounts, and driveshaft.

[JoeH]

+1 on the engine brake. It'll make a big difference. 1) cuts shift time to less than half, and 2) Jake keeps the turbo spooled up a bit.  I would try that before swapping transmissions. Makes the maxidyne & maxitorque a real heal climber. 3) when you use Jake to slow down through your curve it can keep your turbo at 10psi boost if your RPMs are kept at1800+ for long enough.

Note his problem isn't low end, it's 40+ mph.

 

Edited December 31, 2018 by JoeH

[navypoppop]

The finest truck I ever drove for overall performance and power was an R model with 300 Maxidyne, 2 stick 6 speed and it had 4.17 rears on 22.5 rubber. The power you had combined with decent fuel economy made it a great combination for a smaller stance engine compared to some of the larger trucks out there. It was not supposed to be like the Western Star I drove later with a KT600, 13 double OD and 4.10 gears on 24.5 tall tires. That was a beast and the thirstiest truck I ever drove. Long live true Macks.

[Mike Donohue]

Being new to a Mack , one of the things that no matter the horsepower is the fact the Mack power curve is very flat and will never "feel" like you are accelerating. One of the first issues when new to the brand for many!