Allison 1000's sixth gear.

[ford2chevy]

Whats the latest on getting 6th gear to work. I think this is something people should be working on. Should be able to get 25-30mpg with a sixth gear. I haven't heard much about it.

[walkerkd]

yea ive only heard rumors does the 1000 really have a sith gear? i cant find anything on it at all..

[Searay90]

No the 1000 does not have a 6th gear ;) But it sure needs one!! GM should have given us an option for a 3.42 rear gear in these trucks with an overdrive lock out switch. That way the overdrive would pull the rpms down to around 1800 when running lightly loaded, and allow us to use the 4th gear at 1 to 1 to pull the big loads and keep the engine up in its power band and eleminate the "shift hunting" between overdrive and 4th gear that we have now.

Dodge recommends the 3.55 for the cummins for the same reasons.

[hoot]

Yes it is capable of a sixth gear.

It would require another solenoid/valve body and reprogrammed computer/s

I has to do with the way it's designed, clutches and planetaries. Different combinations of apply on different clutches gives you the gears. There is another combination that's not used that will yield a sixth gear.

Search the forum cause this was brought up before.

[SoCalDMAX]

Yes indeedy, Hoot is right as usual.

This was a topic of much discussion in months past. The gearset/clutches are already there, the valve body needs a solenoid and valve, and the TCM needs to be programmed to use it.

The 5th gear is .71:1, the 6th is .61:1. In a previous post I worked out the RPMs for different speeds using stock tires and 33's. IIRC, 70mph with stock tires dropped from 2500rpm to about 2100 or so.

Of course, expect some downshifting from 6th gear when towing 20,000lbs up Donner Pass... ;)

ATS already has a new "beefed" valve body ($630) which allows 5th to handle substantially more power as well as an electronic torque lockup ($250) and a "Triple Lok" torque convertor ($1370) which can probably take all the power you can throw at it. I emailed and asked if they were working on the 6th gear, no answer.

Not that I'm watching closely or anything... ;)

Regards, Steve

[NickLeinonen]

does anyone know how many planetary gear sets the 1000 has?

in theory, a single planetary gear set can produce 7 ratios [including 1:1], but in practice, you can only get 2-3 ratios out of it. it all depends on what is held, and what is driven.

[billnourse]

Steve,

You posted that with stock tires you figured a drop from 2500 RPM to 2100 RPM at 70 mph with the 6th gear. Something doesn't seem right here. Mine is 1900 RPM at 65 MPH and 2100 RPM at 70 MPH now with everything stock????

[tmg115]

billnourse mine is the same way. at 70MPH my RPM's are 2000 and at 65 i am at 1800 RPM's

[NickLeinonen]

that pic kinda looks like 4 gear sets. the green, purple and orange ones are real easy to see, but there may be a gear set in the yellow area. i see a few clutch packs there. maybe not.. but with those 3 gear sets, you can easily get 6 speeds [2 different speeds per gear set] and that's with no gear set compounding. compound them and you can have a massive amount of gears avalable, but that is not practical. mmm, 6 speed... then gm would have to one-up the auto by offering a 7 spd stick, or how about a 10 spd overdrive with 3.23 gears.. just think 120 mph @ 1800rpm.. lol..

[SoCalDMAX]

Hi Guys,

Sorry about the mistake, I was thinking 80mph and typed 70mph. So the 6th gear would let you cruise at 80mph at 2150rpm or so. Not too shabby.

Regards, Steve

[SledZep]

Could it be that GM will hold their cards till someone else puts an actual Heavy Duty Diesel/Auto on the market and one up them with a sixth gear??
Sounds like the TCM is the hardest part. If GM did it maybe we could update ours....

BUT, then "Edge" would have to sell the "Juice" with a full ground effects package to keep the trucks on the ground.....

;) :D

[TBC]

SeaRay you need to take you truck in and have the tranny reprogramed to eliminate the shift hunting problem. It works great afterwards. It can be done at Classic Chev in Grapevine while you wait if you will call ahead.