ally 5 speed mod to 6 speed

[n2dmax]

hello everyone was just wondering if you can change a 2005 lly 5 speed allison into a 6 speed?is it cost efficient ?does it gain more mpg?will ir take more hp and torque!!!LOL Just had to ask.any info would be greatly appreciated.thank you.

 

[Woody35]

you can but im pretty sure its very expensive. ATS has a kit for it i think

 

[CtChevy427]

Its doable and Woody is right its not cheap. Check out this link from one of our vendors.

http://www.alligatorperformance.com/0105-duramax-speed-conversion-p-2904.html

 

[trouttrooper]

Ya, I wish it was just a couple hundred dollar thing. I'd love a second overdrive.

 

[n2dmax]

what would be better the conversion or just simply going to a bigger tire size to get your rpms to 2000 at 74 mph (the speed that I drive on interstate 40)currently I am using stock tires and am doing 2350 at 74 mph and which one would get the better mpg???

 

[Ed HD]

Larger tires lead to worse mileage, from what most of us have seen. Our 05 dropped 1-2 mpg when we went from 245's to 265's.

 

[bighawg]

Here's the one from Suncoast.

ALLISON 5 SPEED TO 6 SPEED
2003-05
Part No. A1-6VB-TCM
Price: $1648.00* CONVERT YOUR 2003-2005
ALLISON 5 SPEED TO 6 SPEEDS
Drops 325 engine rpm @ 75 mph with 3.73 gears. Increases fuel economy 1 - 1.5 MPG, reduces engine noise while cruising, a truck with 3.73 gears
that normally likes cruising at 62 MPH will now cruise nice at 72 MPH. The gear ratio in your 5 speed is .71 and our 6th gear will be .61. 6th gear can be disabled with your two haul button and 5th canceled with OD off. Requires valve body and tcm change (1 hour). No wiring, no modifications required. Indicate LB7 or LLY & year.


http://www.suncoastconverters.com/gmc/gm_products.html

 

[stacks04]

tire size will help if you never had to start/stop. or if you did alot of long distance highway driving. i average about 19 with my truck with 285's on it.

 

[SfcJones]

when I put larger tires on my truck....I lost some on milage, but it looks better.

 

[stacks04]

no doubt about it tim

 

[n2dmax]

my truck is a regency conversion and my dually tires on back are 215/85/16 and the ones on front are 17inch .most of my driving is interstate .I have checked the aspect ratio on them and they seem to be around 30 inch is this anywhere close to stock???????help!!!!I will get the numbers of the 17 inch on front tomorrow .and yes it is a four wheel drive!!!!