Diesel Place banner

1 - 10 of 10 Posts

·
Registered
Joined
·
15 Posts
Discussion Starter #1
I have 2 '05 trucks with lly and 5 speed allison, one is a silverado crew cab and I have the suncoast 6 speed conversion in it, works good, dont like that i cannot get into the tcm to change shift points or tire sizing. my other truck is a custom build tahoe with the lly and allison. since I built it, i wanted to do the six speed conversion, $2k from suncoast was not an option again. What I have just completed is a 2006 6 spd valve body swap into the tahoe, was some custom fab work on the tcc solenoid and valve, and swap the trim solenoids. other than that, its a bolt in mod. confirmed its working tonight and no issues or codes. I then swapped the tcm from silverado to see if 6th gear will work, and again all is good.

my question is, now that I have confirmed this conversion to work, I need to get a tcm for the tahoe rather than swapping tcms between trucks. other than suncoast, is there any where else to get a tcm to be custom programmed for 6th gear. ultimately I would like to beable to change shift timing and tire size for the tahoe any time, IE unlocked tcm.
 

·
Registered
Joined
·
15 Posts
I have been looking into this and came across transmissiontuner.com but I couldn't find much info on his stuff.

Was hoping it might be an alternative to the suncoast stuff.
 

·
Registered
Joined
·
797 Posts
I have been looking into this and came across transmissiontuner.com but I couldn't find much info on his stuff.

Was hoping it might be an alternative to the suncoast stuff.
I came across his site as well but wasn't able to find any info.


I would love to do a 6 speed conversion to mine but that $2000 price tag is hard to swallow especially for a locked TCM. I've yet to actually find what shift points are used by suncoast in their 6 speed conversion TCM. I know for a fact stock 6 speed Allison shift points will not shift right in a LB7 application unless the ECM tuning is adjusted accordingly. The problem is the 6 speed shifts are much higher at part throttle and it will hang like crazy and you have to lift to make the upshift. I like the higher part throttle shifts and have adjusted my ECM tuning to work pretty much flawlessly with the 6 speed shift points but it took a lot of trial and error to make it work right without a hair trigger throttle pedal.


Subscribed for more info.
 

·
Registered
Joined
·
15 Posts
Discussion Starter #5
got it done

I have successfully completed this conversion. I used a 2007 valve body that I modified some parts to work with the 2005 computer and wiring. I contacted several programmers and I got a successful calibration to allow 6th gear to work in the AL5 TCM.

Allison and GM Medium duty says this can be done, but the transmission and yr of truck has to be after July 05, this is when the 6 speed was built, and several medium duties did not have the 6 speed active, this was also using the newer TCM thats not compatible with the 05 trucks.

persistence and determination will get the job done, I now have a Tahoe with an LLY Duramax/ Allison 6 speed using the 05 AL5 TCM, as well as a full floating 11.5 inch rear.
 

·
Registered
Joined
·
15 Posts
I have successfully completed this conversion. I used a 2007 valve body that I modified some parts to work with the 2005 computer and wiring. I contacted several programmers and I got a successful calibration to allow 6th gear to work in the AL5 TCM.

Allison and GM Medium duty says this can be done, but the transmission and yr of truck has to be after July 05, this is when the 6 speed was built, and several medium duties did not have the 6 speed active, this was also using the newer TCM thats not compatible with the 05 trucks.

persistence and determination will get the job done, I now have a Tahoe with an LLY Duramax/ Allison 6 speed using the 05 AL5 TCM, as well as a full floating 11.5 inch rear.
Would you care to share more details on what you modified?

What medium duty did you get the calibration from?
 

·
Registered
Joined
·
2 Posts
5 to 6 speed conversion kit

There are a few sellers of these kits but as you know the prices are ridiculous! The TCM & valve body are just parts?! Does anyone know who makes these parts and where they could be bought wholesale?
 

·
Registered
Joined
·
1,244 Posts
Buying these used would be the lowest price. I can get these these from GM Assembly plant at there cost. Do you know someone that's Able to buy these at wholesale?
GM Part :24256864 MODULE, Control Module, MODULE,TRANS CONTROL $10
GM Part :29543333 VALVE, CONTROL(W/BODY & VALVE) $175
Even at my price for these parts I will never do this conversion for my truck.
It's still not justified.
 

·
Registered
Joined
·
1 Posts
Bringing up an old thread, did anyone ever figure out the changes he made to the 6 speed valvebody to make this work? I have a valvebody out of an 06 core trans I would like to use in an LLY fkr the 6 speed conversion.

Sent from my SM-G975U1 using Tapatalk
 
1 - 10 of 10 Posts
Top