I was just curious as to if anyone on here as any information about converting the current 5 speed ally to a 6 speed ally. I was talking to a buddy about it shortly and he mentioned somehthing about them haveing the same valve body as the 6 speed manuals and can be converted to make them a 6 speed auto. Any insite or information would be great. Thanks

Didnt know a 6sp manual had a valve body?? An allison has the capability to have a 6th gear. I will try to post some more info tonight about it.

I must of missunderstood then. I look forward to reading more about it. Thanks

I was just curious as to if anyone on here as any information about converting the current 5 speed ally to a 6 speed ally. I was talking to a buddy about it shortly and he mentioned somehthing about them haveing the same valve body as the 6 speed manuals and can be converted to make them a 6 speed auto. Any insite or information would be great. Thanks


There is no "valve body" on a six-speed manual - it has a lever. There IS capability for the Allison 1000 tranny to have a sixth gear, but it is not implemented for our use. It would require an additional solenoid and some pieces in the valve body (not a problem, Allison parts) BUT would also require a custom wiring harness AND a custom programmed TCM to make it work in our trucks - (BEEG PROBLEM!)

the case in the 1000 series would not accept it with out extensive mods...need to turn it on hydrolicaly (sp). Everything else is there...

If added to future models, GM would once again have an exclusive tranny design, as they did with the 5 speed auto in '01.

Info in the vocational series thread.

The other gear is a super low 1st for getting big loads moving with the medium duty trucks that GM never enabled.

One would think GM would tweak the gear ratios for the lighter duty pickup market. Our current Allison 1st gear is already a pretty low geared ratio.

if the ally added a sixth gear, its another o/d

The other gear is a super low 1st for getting big loads moving with the medium duty trucks that GM never enabled.

Would makes sense. The gear spread on the HD Alli 2000 is touch too big. Another gear lower than the 1000's set would have been a much better choice for the bigger loads. However, I see the 3000's do have an extra OD, so that is where the extra gear would go. To get that extra grunt you would have to regear the axles.

I think the 6 speed manual he was talking about is the construction version that uses a push button gear selector to shift gears.

A 2nd overdrive would be great. I am sure these trucks would get better fuel mileage with a higher gear.

A 2nd overdrive would be great. I am sure these trucks would get better fuel mileage with a higher gear.





Not mention they run out of RPM at 120mph.


Sometimes I'm in a hurry.

Your in luck Mcrat, w/ a .61od,285 tires and 4000rpm u would be over 172mph http://www.dieselplace.com/forum/smileys/Evil Smile.gif





Guess u could run it against the z06 and see which has the top speed.

My son-in-law works at allison and is working with the 1000 group. The 06 will be a 6 speed which is and extra OD. The only difference is the valve body and TCM. Already looking into the possibleity of swapping over to the new valve body. My guess is it will work because that is the only difference between the WT version and our 1000. I would have to ask him again how it all works but I do nknow its just a matter of clutch configurations while shifting. You would not beleive how thick his book is. I bet its at least 8-10 inches thick.

GregEdited by: LanduytG

The '06 D/A combo sounds like it will be the cream of the diesel crop. Sure hope they research the best ratios for towing and fuel economy. And the 6 speed Allison would give GM a chance to sell the 5 speed Allison scraps to Dodge. http://www.dieselplace.com/forum/smileys/Big Smile.gif

Yeah! One more overdrive for the highway! http://www.dieselplace.com/forum/smileys/Approve.gif


Of course a two-step overdrive cancellation switch....