Allison 1000 5 speed gear ratios

[eric777]

What are the gear ratios for the 5 speed Allison 1000 transmission (used in 04 duramax). I can find info only on the newer 6 speed Allision 1000 here (http://en.wikipedia.org/wiki/Allison_1000_transmission)

Thanks!

[77TransAm]

First five gears are the same, as nothing substantial changed in the planetary gear set. (IIRC, they changed the helix angle on the gears for noise reduction, but that has no effect on gear ratio.) Sixth gear is just an additional overdrive that could not be applied until they added the new solenoid to the valve body.

[77TransAm]

Not necessarily. If the unit was built before June, 2003, it did not have modulated main pressure, and therefore does not have the main mod valve body or the G Solenoid. There is no way to get six speeds without that solenoid. If I remember correctly, GM incorporated that as a mid-year change in '04, so a 2004 truck could possibly either have the solenoid, or not have the solenoid, depending on the build date.

Regardless, the answer to the original question is not affected. The gear ratios on ranges 1-5 did not change with the inclusion of the 6th range.

[eric777]

Ok, thanks!

I am sure you all have seen the 6-speed conversion kit available for the 1000. Here is a link where it is briefly discussed. LINK (http://www.thedieselgarage.com/forums/showthread.php?t=28070)

Pretty expensive though.