Page 1 of 2 12 LastLast
Results 1 to 20 of 27

Thread: 5speed to a 6speed

  1. #1
    Join Date
    Mar 2000
    Location
    St. George, Utah.
    Posts
    980

    Talking 5speed to a 6speed

    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
    2018 GMC Denali HD 2500 L5P.

  2. #2
    AKMark is offline Building another 6.2L powered vehicle
    Join Date
    Dec 2006
    Location
    North Pole, Alaska
    Posts
    400

    Default

    Interesting, what did you have to do to turn it on?
    05 2500HD CC LB LLY, 4x4, 3.73s 235/85R16's, webasto cab heater, to keep it warm.
    03 Buick Rendezvous - When you average over 80 miles per day driving around, you need one of these.
    85 K-5, 6.2, SM465, Rockwell T221, 1 tons, 36's. More goodies to be installed as time and money allows.
    82 K20, 6.2, SM465, NP208, stock except for bed rack, snow plow, and glow plugs are on a toggle switch. It works great for plowing!
    72 Postal Jeep - Yet another project

  3. #3
    Join Date
    Mar 2000
    Location
    St. George, Utah.
    Posts
    980

    Talking

    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
    2018 GMC Denali HD 2500 L5P.

  4. #4
    Join Date
    Mar 2000
    Location
    St. George, Utah.
    Posts
    980

    Default

    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
    2018 GMC Denali HD 2500 L5P.

  5. #5
    AKMark is offline Building another 6.2L powered vehicle
    Join Date
    Dec 2006
    Location
    North Pole, Alaska
    Posts
    400

    Default

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

    No worries, just figured I'd ask.
    05 2500HD CC LB LLY, 4x4, 3.73s 235/85R16's, webasto cab heater, to keep it warm.
    03 Buick Rendezvous - When you average over 80 miles per day driving around, you need one of these.
    85 K-5, 6.2, SM465, Rockwell T221, 1 tons, 36's. More goodies to be installed as time and money allows.
    82 K20, 6.2, SM465, NP208, stock except for bed rack, snow plow, and glow plugs are on a toggle switch. It works great for plowing!
    72 Postal Jeep - Yet another project

  6. #6
    Join Date
    Jan 2001
    Location
    Knoxville,Tennessee
    Posts
    2,639

    Default

    Inspector,

    Will changing the Vin in the ECM cause any problems when getting a smog check?
    "The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government."
    -Patrick Henry


    A5150nut
    2006 K3500 D/A
    94 6.5 4x4 5spd Sold

  7. #7
    Join Date
    Apr 2001
    Location
    CA
    Posts
    13,573

    Arrow

    Quote Originally Posted by a5150nut View Post
    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.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  8. #8
    Join Date
    Mar 2000
    Location
    St. George, Utah.
    Posts
    980

    Default

    What D Max said.
    Denny
    2018 GMC Denali HD 2500 L5P.

  9. #9
    Join Date
    Mar 2000
    Location
    Willits, Ca. U.S.A.
    Posts
    474

    Default

    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.
    2004 G.M.C. LLY CC D/A sb 4wd Summit White, ATS Duals, BD X-monitor, BD Exhaust Brake, Snugtop shell, 45 gal. Transferflow fuel tank, AFE stage II
    2004 TDI Jetta GLS S/W
    2005 TDI Passat GLS S/W
    2020 GMC Denali 2500HD

  10. #10
    Join Date
    Jun 2000
    Location
    Morrisville, VT, USA
    Posts
    2,399

    Default

    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?
    2008 Jaco Seneca 35' motor home (Kodiak 5500 chassis). Pulling 18' Wells Cargo enclosed trailer, with 2016 Miata in it.

  11. #11
    Join Date
    Mar 2000
    Location
    Willits, Ca. U.S.A.
    Posts
    474

    Default

    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.
    2004 G.M.C. LLY CC D/A sb 4wd Summit White, ATS Duals, BD X-monitor, BD Exhaust Brake, Snugtop shell, 45 gal. Transferflow fuel tank, AFE stage II
    2004 TDI Jetta GLS S/W
    2005 TDI Passat GLS S/W
    2020 GMC Denali 2500HD

  12. #12
    Join Date
    Mar 2000
    Location
    St. George, Utah.
    Posts
    980

    Question

    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
    Last edited by Inspector; 12-02-2012 at 22:07.
    2018 GMC Denali HD 2500 L5P.

  13. #13
    Join Date
    Mar 2000
    Location
    Willits, Ca. U.S.A.
    Posts
    474

    Default

    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.
    2004 G.M.C. LLY CC D/A sb 4wd Summit White, ATS Duals, BD X-monitor, BD Exhaust Brake, Snugtop shell, 45 gal. Transferflow fuel tank, AFE stage II
    2004 TDI Jetta GLS S/W
    2005 TDI Passat GLS S/W
    2020 GMC Denali 2500HD

  14. #14
    Join Date
    Mar 2000
    Location
    St. George, Utah.
    Posts
    980

    Default

    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
    2018 GMC Denali HD 2500 L5P.

  15. #15
    Join Date
    Mar 2000
    Location
    Loyal WI US
    Posts
    10,792

    Default

    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.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

  16. #16
    Join Date
    Mar 2000
    Location
    Willits, Ca. U.S.A.
    Posts
    474

    Default

    Quote Originally Posted by Kennedy View Post
    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.
    2004 G.M.C. LLY CC D/A sb 4wd Summit White, ATS Duals, BD X-monitor, BD Exhaust Brake, Snugtop shell, 45 gal. Transferflow fuel tank, AFE stage II
    2004 TDI Jetta GLS S/W
    2005 TDI Passat GLS S/W
    2020 GMC Denali 2500HD

  17. #17
    Join Date
    Mar 2000
    Location
    Loyal WI US
    Posts
    10,792

    Default

    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.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

  18. #18
    Join Date
    Mar 2000
    Location
    St. George, Utah.
    Posts
    980

    Talking

    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
    2018 GMC Denali HD 2500 L5P.

  19. #19
    Join Date
    Mar 2000
    Location
    St. George, Utah.
    Posts
    980

    Red face

    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
    2018 GMC Denali HD 2500 L5P.

  20. #20
    Join Date
    Mar 2000
    Location
    St. George, Utah.
    Posts
    980

    Talking

    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
    2018 GMC Denali HD 2500 L5P.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •