5speed to a 6speed

[Inspector]

I went and did it. I just had my 1000MH 5 speed trans TCM reprogramed to allow the 6th speed turned on. I am stoked. After the procedure we put it on the freeway and counted the shifts. They were all there and 6th dropped 400 RPM. 5th at 65 was 2350 and now it's 1950. Nice smooth shifts. Hopefully some milage increases will come along with the reprogram. We are going to drive to Florida in Feb so we'll see.
Denny

[AKMark]

Interesting, what did you have to do to turn it on?

[Inspector]

Being an 06 I had to have a Vin # of a medium duty that had an active 6 speed. Those vins would be from a mid year 07 to present. The vin # that I used was from an 08. I found a tech that had a GM diagnostic tool called a Tech II and he hooked into the OBDII port and selected the TCM in the truck and replaced my vin # stored there with the vin of the 08. It took about 10 minutes to replace the tables and activate the dormant sixth speed. In 06 all the pickups got the 6 speed but it wasn't until mid 07 that the medium duties got it. Most probably 05s and before won't have the capability to be reprogrammed just with the TCM but can have the valve body and solenoid rail replaced along with a programmed TCM of the 4th generation series installed and then your set albeit at some expense. Good luck
Denny

[Inspector]

AKMark:
The easiest way to tell if you can just do a flash of TCM for sixth is to look on the drivers side of the trans and if you see the NSBU there then it can't be done. On those transmission that can be done the NSBU is internal.
Denny

[AKMark]

Cool that it worked for you. My 05 has the external NSBU, so no 6-speed.

No worries, just figured I'd ask.

[a5150nut]

Inspector,

Will changing the Vin in the ECM cause any problems when getting a smog check?

[DmaxMaverick]

Inspector,

Will changing the Vin in the ECM cause any problems when getting a smog check?

Only the TCM is reprogrammed, not the ECM/PCM. The TCM VIN has to be "changed" before the later model calibration will be accepted and installed.

Incidentally, I did my smog inspection today. $57 paid to look for smoke.

[Inspector]

What D Max said.
Denny

[tpitt]

In the earlier Duramaxs you can change the valve body and TCM to convert to a six speed. I've done this to mine some time ago. I just returned from a 2000 mile towing trip, and feel in those circumstances the 6th gear didn't do me any good. I towed mostly in 5th gear.

[DickWells]

This is interesting. Haven't read anything about it in a long time, and never have read, before, a report from anyone who had done it.
What is the size and weight of your trailer? And, is it still a $2000~ proposition?

[tpitt]

My trailer is about 8300 lbs. but when I'm full of fuel and my goodies in the pickup, I'm guessing the pickup will weigh just shy of 9000 lbs. I carry around 120 gallons of fuel. Not an overly amount of weight, but I also went to 265 tires.

Just got back from a trip to Canada, and haven't figured out the mileage yet. Was driving in some severe weather with lots of wind and rain.

[Inspector]

I just reread Tpitt's post and realized that he was pulling with a pickup. When I finished the reprogram I took it out on the freeway for a test and to make sure that 6th gear was actually there. The motorhome is winterized so no water and no road load so pretty light. I did have a full tank of fuel (80 gals). It appears that his gross weight was about 18,150.
I would estimate that my gross weight at around 16 to 17 k. My truck had no trouble staying in 6th and ran quite easily. I have since hooked the edge back up and took her out again and with the added power I'm looking forward to seeing how it will do road loaded and with the toad following close behind . My GCWR will probably be right at 25 to 26k. We'll then see how it holds 6th. In the mountains maybe would explain why he was not able to hold. 6th.
Denny

[tpitt]

Dennis, I'm pulling with a LLY with the Edge set on 2 most of the time. Yes we were in the mountains, fighting severe weather, There were warnings out for R.V.s and trucks. I would imagine your motorhome to be lower geared. One thing that hinders me is the low speed limit here in the west for pulling trailers. 6th gear is just too high. I could hold 6th gear on the level or slight grades, but chose not to pull my pickup that hard at lower rpms.

Empty I've gotten better than 21, bone stock without the Edge installed, and this wasn't driving for fuel economy. I believe if I drove it slower I would get close to 23.

I would guess my weight to be around 17000 to 18000lbs. I wanted to weigh it this trip, but we were in moonsoon type weather.

[Inspector]

I will be very happy if I can average 10. I have seen 10.3 and 10.6 a couple of times hand calculating but probably average in the nines. I haven't put all the numbers together for an average. This spring I will be using an I pad app to follow my costs and fuel usage. Should be interesting. Hopefully I get a lot of 6th gear driving.
Denny

[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

[Inspector]

We refueled in Van Horn Texas and with the help of the infamous west Texas winds even though we doing a lot of up and down in the west hill country on I 10 we noted 11.5 mpg. The six speed upgrade hung right in there at 65mph. I'll check in again tomorrow night.
Denny

[Inspector]

Refueled in Van Horn, overnighted in Ft. Stockton, drove on to San Antone. Clocked 456 miles. Fueled up in New Braumfels 40.51 gals. Worked out 11.3-----. Light winds today but the west Texas hills reminded me of I 80 through Iowa. Were staying in San Antone tonight.
More tomorrow
Denny

[Inspector]

We have traveled a ways since the last post. We are now in Natchez MS to tour some old Antebellum homes. From there we go on to Pensicola to tour the Navy air museum. Looking forward to that. Mileage is holding up with an average in the high tens. Pert near got a twelve once and still holding out for at least one of those. If we don't stop and go touring elevens are easy. I will check in down the road.
Denny

[Inspector]

Well the cruise was wonderful and I still don't have my land legs back yet.
We are going to hang out in Winter Garden FL for a couple more days and then start back west. We will be going north through Tenn for visit with relatives. I will begin tracking mileage when we hit the road again.
Denny

[Mark Rinker]

Hey Denny. What was your mileage before you upgraded to the Edge? Exhaust?

[Inspector]

Hi Mark:
I'm thinking 7 to 9 with the 5 speed. I've always had the edge on the truck so can't give figures on that but suspect not much worse. The exhaust probably gave more consistent 9s. The sixth speed upgrade here in the west kicked it into the 10s. Our trip to the south east produced an average of 9.37 with a best of 11.99 and worse 7.63. Performance was great. In the East as you know is not flat with continual rolling hills that kill mileage. I kicked the edge up to level 4 and it would then hold sixth easily through those hills. We drove through the Smokeys and i was surprised at just how well it pulled those grades. Temps were well controled. Tranny never topped 170 and eng temp stayed below 215 and most of the time 190 to 195. EGTs never above 1150 most of the time 750 to 900. I used cruise most of the time. If the tranny felt it needed to shift down then it would go to 5th and back to 6th in a very short time. I could count on one hand the shifts down to 4th. Out here in the West level 3 is good. Overall I'm very happy with performance. Now I will concentrate on the suspension.
Denny