5speed to a 6speed

[Kennedy]

OK guys stop and take a deep breath here. Dennis has a Medium duty vehicle built as a 6 speed but calibrated as a 5 speed. The pickups are either 5 or 6 speeds. The 01-05 can be converted to 6 speed by using a custom programmed TCM (proprietary software using unreleased stolen? calibrations from Allison) and a modified valve body.

I did this to my 05 years back. I don't really think it gained me much in terms of MPG, but it does make things quieter. After driving a 6 speed truck and then switching to a 5 speed it just seems "busy" with too much engine speed at cruise.

P.S. the pre-Bosch ECM trucks do not hold 6th as well as the post. Be it superior TQ or simply programming differences, the LBZ up series holds 6th much better and responds much better to increasing loads.

[tpitt]

OK guys stop and take a deep breath here. Dennis has a Medium duty vehicle built as a 6 speed but calibrated as a 5 speed. The pickups are either 5 or 6 speeds. The 01-05 can be converted to 6 speed by using a custom programmed TCM (proprietary software using unreleased stolen? calibrations from Allison) and a modified valve body.

I did this to my 05 years back. I don't really think it gained me much in terms of MPG, but it does make things quieter. After driving a 6 speed truck and then switching to a 5 speed it just seems "busy" with too much engine speed at cruise.

P.S. the pre-Bosch ECM trucks do not hold 6th as well as the post. Be it superior TQ or simply programming differences, the LBZ up series holds 6th much better and responds much better to increasing loads.

I believe we already knew this. I actually can hold six gear fairly well. I chose not to as a truck driver equipment operator, I don't believe in pulling them hard at low rpms. Also with a 55 mph speed limit, unless your on a flat surface its too high geared. I experimented both ways 5th or 6th and depending on the terrain and the wind determined which gear I cruised in.

You might check with Suncoast and ask them if they stole allison programming. I do not know. I expect a person could and has said the same thing about headlight harnesses and other various items that other companies developed.

[Kennedy]

Discussions like this even though in a Medium Duty forum gets a lot of people's hopes up especially when there is only one Med duty owner and the rest of the participants appear to have pickups at least based on signatures.


Maybe leaked would be a better choice of words on my part. Word is the intellectual property walked out the door with a former employee. Nevertheless it did not hit the streets because Allison wanted it to.

Again I instaled on in my own truck and liked it enough that we've sold several after this. I try to point out though that MPG differences have not been worth writing about. My guess is that this is more emissions related in regards to slowing down engine speed.

To answer the question on price yes that are nearly $2k but if you are having a Suncoast built transmission there discount available.

[Inspector]

Thanks John for for your input as is always appreciated. I'm probably the only active guy here on the DP with a medium duty and I sure enjoy it. As you can see from my sig that I have made a few improvements but nothing monstrous. My next thing will be to install the tap shifter. It's in the mail. We'll see how it goes.
Denny

[Inspector]

After much research and input by folks that know I am realizing that the tap shift is not an option. First of all we don't have a BCM as the pickups do and a couple of other module that figure into this whole control picture. So I'll just be happy with the fact that I have a active working sixth speed. I would be happier with the tap though.
Denny

[Inspector]

I've had it on the road now for a while and love the way it shifts. The one thing that I was afraid of was when down shifting it would go thru fifth to fourth. That has not happened. It will when it needs to use fifth and then back to sixth. It holds sixth very well even on more than slight upgrades. Overall very satisfied with this upgrade. At 65 I'm taching 1950 rpm and it seems as though the truck is just loafing. I'm putting together mileage figures and will post the results after a few more tanks.
Denny

[Inspector]

Put 458 miles on and 47.7 gals. Calced to be 9.6 mpg. The weather here in southern AZ and NM is terrible wind and rain mostly continuous for the past three days. We have stopped for the night in Lordsburg NM. I'll post every night until a solid average is known.
Denny