I was at the shop recently getting some info for upgrades to my truck (exhaust, chip, etc) and they told me that the 2004 Allison trans (5-speed) has the 6-speed hardware and that you can upgrade the controller to get use of the 6th gear.

Anyone heard of this? Is it true? I have an '04.5 LLY.

I was at the shop recently getting some info for upgrades to my truck (exhaust, chip, etc) and they told me that the 2004 Allison trans (5-speed) has the 6-speed hardware and that you can upgrade the controller to get use of the 6th gear.

Anyone heard of this? Is it true? I have an '04.5 LLY.

Old wives tale.

there was a wire added and a solinoid I believe and of course programing to lower rpms 200 when it shifts into 6th gear ,only over 90 kph(45mph)its like a torque converter engagment IMHO ,only a milage thing

No wire, no solenoid added. It is another overdrive gear.

I think I have it ,but mike L SAYS NO WAY.....i COUNT 6 HE SAYS 5...been there done that-...JMO-michael

mike,isn't it that gm changed the valve body to make it a 6spd?,,i thought these trannys could be 4,5 or 6 spds thru programming?,and that they just use diff applys to get diff gears?

I think I have it ,but mike L SAYS NO WAY.....i COUNT 6 HE SAYS 5...been there done that-...JMO-michael

It feels and sounds like a 6th gear but it's just the torque converter locking up. To be honest, I can't always tell which "shift" is actually the tc locking up. (I think it's the 2nd to the last "shift" if you're under steady acceleration from a stop, not in tow/haul, in other words 1-2-3-4-lock-5).

6spds are 6 spds +converter lockup,5spds are 5spds +converter lockup

6spds are 6 spds +converter lockup,5spds are 5spds +converter lockup

Exactly.:D

In a 6-speed, which shift feel is actually torque converter ??

Takes more than programing...
http://www.suncoastconverters.com/gmc/LCT%201000/allison5to6.html

there is a diff valve body too

tc is ramped on thru a pwm(pulse width modulated) solenoid so you won't feel it

I was at the shop recently getting some info for upgrades to my truck (exhaust, chip, etc) and they told me that the 2004 Allison trans (5-speed) has the 6-speed hardware and that you can upgrade the controller to get use of the 6th gear.

Anyone heard of this? Is it true? I have an '04.5 LLY.

I have no idea if this is true, but FWIW I was told this same thing by a GM mechanic last week. He also said there is one more unused gear in my 6 speed Allison, which would mean you have two unused gears. I am told by someone I trust that this particular mechanic is a diesel specialist and as good as they come.

It's true, all 5 speed allisons have the 6 speed capablities. Only differance is the valve body and programming. The 06 and up valve body is needed along with custom tuning. I am looking into building a kit for the 8100 trucks also. To get 6th gear GM reapplies the 2nd gear clutches. And the only differance is the 06 and up valve bodies is there is an extra 6th gear tube, that supplies the valve body full line pressure straight on the 2nd gear clutches to keep them from slipping while appling power.

Wow - lots of differing opinions...

Mike L - It seems that the link that WanaDMXsub provided provides a Valve body and TCM that upgrades from a 5 speed tranny to a 6 speed. I assume this means "plus overdrive" just like when you had a 5 speed. This is a bit more than I am planning to spend to get the "6th gear" - at least right now, but it would seem to suggest an unused gear is available.

Lame question I suppose, but what is the real difference between another gear and overdrive?

prostock1455 - is this really a $2300 upgrade? or is there another option?

Well, I am not spending the $2300 for that upgrade. I purchased the complete 6 speed Valve body from GM for $677. It will bolt right in and it will even function like the 5 speed until I monkey with the TCM to include the 6th gear data.

The Allison 1000 has always been a 6 speed transmission. I am not sure why Allison/GM cut it to a 5 speed trans.

. . . I assume this means "plus overdrive" . . .
but what is the real difference between another gear and overdrive? . . .


No, the 5 speed is a 5 speed (including overdrive), and the 6 speed is a speed (including overdrive). Some of the discussion is that it FEELS like there another one, but it's just the torque converter locking.

"Overdrive" has 2 basic meanings. In the old days, it was a separate unit behind the transmission that provided a high-range. It was "overdrive" in the sense that its output shaft spun faster than its input shaft. I once drove a '55 Chevy, 3-speed that had the overdrive turned on . . . shocking as hell when I downshifted because nothing happened, it free-wheeled, because it was intended to give better gas mileage, so it would coast when you let off the gas.

For years now, the top gear in automatics have been called "overdrive", and that should mean that the output shaft from the transmission spins faster than the engine. So now days, it's generally just the top gear.

No, the 5 speed is a 5 speed (including overdrive), and the 6 speed is a speed (including overdrive). Some of the discussion is that it FEELS like there another one, but it's just the torque converter locking.

"Overdrive" has 2 basic meanings. In the old days, it was a separate unit behind the transmission that provided a high-range. It was "overdrive" in the sense that its output shaft spun faster than its input shaft. I once drove a '55 Chevy, 3-speed that had the overdrive turned on . . . shocking as hell when I downshifted because nothing happened, it free-wheeled, because it was intended to give better gas mileage, so it would coast when you let off the gas.

For years now, the top gear in automatics have been called "overdrive", and that should mean that the output shaft from the transmission spins faster than the engine. So now days, it's generally just the top gear.


Exactly,

The 5 speed has one overdrive gear and the 6 speed has two overdrive gears. Both transmissions have the exact same gear ratios up to 5th gear, the 6 speed simply has one more higher ratio gear beyond 5th gear.

Good info here:

http://www.dieselplace.com/forum/showthread.php?t=176323&highlight=Allison+gear+ratios

Well, I am not spending the $2300 for that upgrade. I purchased the complete 6 speed Valve body from GM for $677. It will bolt right in and it will even function like the 5 speed until I monkey with the TCM to include the 6th gear data.

The Allison 1000 has always been a 6 speed transmission. I am not sure why Allison/GM cut it to a 5 speed trans.

:exactly:

MW7 (6spd) valvebody bolts in just fine. Its the programming to apply 6th gear that is impossible to track down. 5th gear is C2 and C3, 6th gear is C2 and C4 IIRC. There is no possibility for 7th gear because the next combination in the lineup (C2 and C5?) would result in a tie-up.

Have any of you dealer guys thought of flashing a 5spd truck with a 6spd tcm program? The trannys are physically the same other than the valve body, makes me think it's just a programming change away.

7spd, now that would be novel. :D

Well, it's been a looooong time since the "tranny wars" and there are now 6 spd valve bodies and conversion kits, but this still applies!

http://www.dieselplace.com/forum/attachment.php?attachmentid=20435&d=1149215843

Where's my toggle switch? :D

Where's my toggle switch? :D

Where's Cougar with that program hack when we really need him?;):D

Where's Cougar with that program hack when we really need him?;):D

:confuzeld

So if the valve body cost $677 from GM then why does the kit cost $2300. Can the programming be added with EFIlive?

Can anybody tell me what the chatter is when pulling a 8000lbs trailer is. This happens only on take off and this past week was the first time it happened. It kind of felt like a clutch with a warped flywheel/ pressure plate.
Anyway, if I have to get into the tranny and I could upgarde to a 6 speed for a grand, well that would be great.

So if the valve body cost $677 from GM then why does the kit cost $2300. Can the programming be added with EFIlive?

Can anybody tell me what the chatter is when pulling a 8000lbs trailer is. This happens only on take off and this past week was the first time it happened. It kind of felt like a clutch with a warped flywheel/ pressure plate.
Anyway, if I have to get into the tranny and I could upgarde to a 6 speed for a grand, well that would be great.

Do you have a 2 piece drive shaft? Drive shaft center support is usualy the culprit.

So if the valve body cost $677 from GM then why does the kit cost $2300. Can the programming be added with EFIlive?

Can anybody tell me what the chatter is when pulling a 8000lbs trailer is. This happens only on take off and this past week was the first time it happened. It kind of felt like a clutch with a warped flywheel/ pressure plate.
Anyway, if I have to get into the tranny and I could upgarde to a 6 speed for a grand, well that would be great.

Suncoast website has them listed at 1248.00.

Thanks Mike,

I'm already under the truck.