5 speed to 6 speed conversion.

ROGUE GTS

Member
Apr 30, 2008
168
0
16
In for updates. Love my lly but this is the one thing i wish it had. Couple updates will keep me from shopping for an lml denali 4x4.

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PULRIG

New member
Jul 30, 2012
2
0
0
Northern California
Anyone running this on a built transmission? I have a BD-Power Trans. Will it work or would it mess up how BD has the Trans. setup? I imagine it would be fine...
 

stibuilder

New member
Oct 16, 2016
239
0
0
Snoqualmie, WA
I sure would like to have TAP Shift on my 06/07 Kodiak with the 6th speed. Drove a LML from Seattle to Oklahoma and back with it, sure made for easy living in the hills.
 

Bustedknuckles

Honey Badger
Sep 25, 2010
1,309
2
38
31
Hagerstown MD
i wouldnt when ran with this 6 speed conversion until dialed in. the 2-1 can be EXTREMELY harsh in the morning, enough it has locked up my tires a couple times. 4-3 lets you know its there but nothing butt puckering. The G3's have always had aggressive downshifts though from what i hear from other people. When i had the stock valve body, these symptoms were there but not near as bad. More of an annoyance in the mornings but it was worth the added strength to me to just ignore it. Right now, no one has a fix for it and honestly, i think alot of guys are not worried about. youre not under power to kill parts.
So a hard 2-1 downshift with alto G3s is somewhat normal? I've built 3 trans with them in C3 and my personal truck has a hard downshift when you first drive it. None of the other trucks do though and all three have the same setup.

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Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
19,364
1,917
113
Phoenix Az
So a hard 2-1 downshift with alto G3s is somewhat normal? I've built 3 trans with them in C3 and my personal truck has a hard downshift when you first drive it. None of the other trucks do though and all three have the same setup.

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C3 clutch pack isnt used in 1st or 2nd gear
 

chevyburnout1

Fixing it till it breaks
Aug 25, 2008
2,368
1
38
Berthoud, CO
Finally swapped tuning and am enjoying it greatly! 6th gear comes in around 57mph slowly accelerating. Holds the higher gears even with more throttle input which even with my build is still great. Besides the stupid Allison cold shift strategy hanging the gears too high, the shift timing seems perfect and my half throttle 4-5 flair has gone away. The transmission may be getting weak but until then it gets the job done!
 

chevyburnout1

Fixing it till it breaks
Aug 25, 2008
2,368
1
38
Berthoud, CO
Also just noticed something this weekend that I can't remember if it was mentioned. But there is a 2nd gear start programmed into the strategy when selecting 2nd gear. Flipping sweet! :thumb:
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
19,364
1,917
113
Phoenix Az
Also just noticed something this weekend that I can't remember if it was mentioned. But there is a 2nd gear start programmed into the strategy when selecting 2nd gear. Flipping sweet! :thumb:

does it actually start in 2nd or do you feel it quickly shift to 2nd soon as you touch the throttle?
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
19,364
1,917
113
Phoenix Az
It starts in first then jumps to second touching the throttle. The 2-1 downshift still seems to be normal when coming back to a stop.

ok, 10-4. i thought maybe Josh found the tables to make it STAY in 2nd gear at all times even at a full stop (think its one of the things he has to search for when hes bored). the 06-up trucks will stay in 2nd when you make a 2nd gear start tune, its just the 01-05 that do this.
 

Frogman1

FROGMAN1
Aug 5, 2017
31
1
8
VA Beach
The 5 to 6 speed Allison swap must be a popular topic this week! I've been searching on other forums and have come to the point where I'm needing guidance before I make a costly mistake. DuramaxTuner.com has got a valve body and TCM swap that should work easy day for $1500. The problem that comes with this is from everything I've read on SunCoast, PPE, and D-MaxTuner, they're all going to lock your new TCM with their programs. An individual has pulled off the valve body swap and modification on his own less getting his TCM tuned and it is NOT Locked. Locked TCM/ECM etc seems like an option I'm trying to avoid as I'm bouncing around from Diesel shop to Diesel shop and will finally get my ECM unlocked from GMC next week so that I can tune it as desired.

Here's what I have going on. 8 months ago I purchased my dream vehicle; an 06' Hummer H1 Alpha with the 05' LLY and 5speed in it. I've been collecting parts for 4 years for another hummer build/conversion. A PPE LBZ and matching PPE stage 5, 6 speed Allison.

1. Can I just swap the newer built 6 speed transmission and TCM into the Hummer?... or will the ECM not communicate well/ prevent it from functioning as a 6 speed in the vehicle?

2. Will the wiring harness from the 05 Allison that's on the "2006" Hummer plug right into the 06 Allison and TCM or is there some deeper modification to the harness as well?

3. Is it just better to go with the package deal from one of the companies and not part the matching engines and transmissions? I know it's easier.

4. What problems will I have, if any, when I try and tune my engine with my PPE or an EFI live tuner and the TCM is locked to one of the diesel companies?

I know this 5-6 speed thread is snowballing. I didn't want to hop on it but forgot how to open a new one. Thanks in advance for any guidance more knowledgeable folks out there might have to help keep me from making a mistake.

Best, Ralph
 

Frogman1

FROGMAN1
Aug 5, 2017
31
1
8
VA Beach
Any takers? to include Duramaxtuner.com? I want to try my PPE tuner out, but have installed a DSP5 for the EFI selectable option. They all will have Allison shift point adjustments.
 

gmc502

Member
Jan 16, 2011
444
2
18
good point Mike.my SoCal tcm(locked) and valve body work great.no need to play w/ anything.
plus I have the Fleece tap shift and that really lets the truck shift at full throttle.