I forgot to mention the Bell is 3:1.

The Allison version will be in the same ball park.

BTW rumour has it the new RXx will be 3.2 litres equivalent so at the
same level of tune as the current 13B  TTC engine we are looking at
800 HP for a two rotor. It is all aluminium stock as well.


Paul Lamar


Paul, you might look at the gear set from a NP241 transfer case, it's
very beefy and it doesn't have a lot of crap attached to it. Ratio is
2.72:1.

Everett Rankin

How much torque is it good for?

Paul Lamar

Torque rating should be high as it is multiplied by the transmission
gears in first or second gear prior to getting applied to the
transfer case. Allison planetary ratios  are 3.59, 3.69 and one is
4.7. These are designed for use in medium and heavy duty trucks,
buses and construction equipment so they are designed for high
torque diesel engines and lots of abuse. The parts are readily
available which says they are fairly affordable. The advantage to
using the higher ratios is that higher engine RPM for takeoff can be
used or lower prop RPM to reduce drag or noise.

Dale Davies

Dale, what are the part numbers for the Allison 3.59? I am thinking
of designing a GB for a 3 rotor turbo Reno racer.


Paul Lamar

I do not know the part numbers. I spent about one hour trying to find
them to no avail. I did find United Transmission Exchange in San
Bernardino, Ca. The phone number is 800-527-1637. E-mail
parts@utxchange.com <mailto:parts@utxchange.com. The Allison MT643
is an older model trans with a max input of 640lb ft. It has a first
gear ratio of 3.58:1. A newer trans is the MD 3060 with a max input
of 900+ lb ft. It has a first gear ratio (close ratio) of 3.49:1.
Being rebuilders they should be able to fix you up.

Dale Davies

Thanks Dale

Paul Lamar

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