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Discussion Starter #1
******Mods make this a STICKY****** Best mod for the money

1. Look at the shift shaft on the transmission. If it does NOT have a electrical switch then you are in luck. (see pic) The transmission has the hardware for six speeds so all you need is the software. (TCM transmission control module reprograming)

2. Call your favorite GM steelership and make an appointment for a TCM reprogramming.

3. When you get to the dealer the GM Technician will need special instructions so they do not reload the 5 speed software. My truck was programmed wirelessly with the GM MDI

4. The Tech will connect to the truck with the service stall computer through the MDI.

5. Load the truck into the computer normally. when it asks you to reprogram or replace and reprogram choose REPLACE AND REPROGRAM.

6. The computer will then show your trucks VIN#. You need to CHANGE the vin to a 2008 model year vin.
-2008 C4500 4X4 VIN# 1GBE4E3968F407111 (I used this vin for my truck)
-2008 C4500 2wd VIN# 1GBE4C1938F404710 (Not sure on gear ratio found vin online)

7. Select Transmission Control Module and click next

8. Its like magic......in about 10 minutes your trans will be a six speed....ENJOY...you will now lower your cruising speed RPM by roughly 400.
Less fuel and less noise.

My buddy worked at the dealer that reprogrammed mine it cost me 60 bucks and I bought him dinner. I got quotes from other dealers for $75 to $125. Oh and the allison dealer wanted $250 and a signed letter from GM.

GOOD LUCK This is a huge improvment, and best of all this program is for the 4500 from allison. It is not a modified 2500 tune, so the exhaust brake and everything works like it did with the 5 speed program.
 

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Discussion Starter #3
Not sure on that one, I guess you would have to talk to the service manager. The major push back I got from other dealers was they said it would'nt work.......Well it does, I proved it. Let me tell you this truck is ten times better on the freeway 2300 rpm at 73mph, major improvement. Wish I would have had it on the 1150 mile ride home.....coulda saved some coin on that trip. I would think if you go into the dealership well educated and explain what you are trying to do they will program it for you. If they wont program your transmission to the tune you want just tell them you will bring your money to another dealer. Just my 2 cents tho. GOOD LUCK.
 

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Hope that didn't come across as "naysayer" just suspicious of how easy it may be.

So have you pulled heavy loads with it? My concern would be if there's enough stock horse power to hold 6th gear with a load not cause the transmission to "hunt". I've wondered if that's why they locked it out in the original tune.
 

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Hope that didn't come across as "naysayer" just suspicious of how easy it may be.

So have you pulled heavy loads with it? My concern would be if there's enough stock horse power to hold 6th gear with a load not cause the transmission to "hunt". I've wondered if that's why they locked it out in the original tune.
Some of the 2006 and early 2007 Kodiak Motor Home owners have 4.78 rear axle. A 6 speed trans will be a big improvement.
 

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Some of the 2006 and early 2007 Kodiak Motor Home owners have 4.78 rear axle. A 6 speed trans will be a big improvement.
That's my concern, my truck has 4.56 ratio. I haven't been able to find any information to understand if this would be a good idea or one I'd regret. If I could do this and retain the ability to lock out the 6th gear when pulling, that could work. I say the 6th gear since locking out overdrive would really mean taking it to 4th gear.
 

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My concern would be if there's enough stock horse power to hold 6th gearQUOTE]

Stock horsepower?? Crank it up. I have EFI Live tune done to mine and the 6th gear reprogram and I drove it to Tennessee last weekend empty. I had my cruise set on 78 mph the whole way and was running 2200-2300 rpm.
 

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Discussion Starter #10
I'm going for longevity and don't think I need additional horse power.
"think" is the key word here.;) After you tune your truck you will wonder why you didnt do it years ago. In my opinion it is a no brainer......at least for a mild tune better power, better fuel mileage, cooler egt's. No, I didnt take it as a "nay sayer". I did PM Jager about how it is with 6 speeds, he also mentioned it would be nice to lock out 6th for towing but said it does not hunt much for gears. I have not had a chance to tow anything heavy yet, My toyhauler is in storage for the winter.
 

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Even my 2500 doesn't hunt for gears pulling a load with the 6 speed and it has 3.73 gears and only runs 1800 RPM at cruising speed. Plenty of power down there, have to watch the EGTs though. The reason for the 4500 is for the way the chasis handles the weight.

This sounds interesting to me, hope I can find a willing dealer....
 

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I wonder since I've put on the taller tires (37") and 70MPH is now around 2000 RPMs if a 6th gear would be too much and it would hunt gears? I have 4:56 gears in rear
 

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"think" is the key word here.;) After you tune your truck you will wonder why you didnt do it years ago. In my opinion it is a no brainer......at least for a mild tune better power, better fuel mileage, cooler egt's. No, I didnt take it as a "nay sayer". I did PM Jager about how it is with 6 speeds, he also mentioned it would be nice to lock out 6th for towing but said it does not hunt much for gears. I have not had a chance to tow anything heavy yet, My toyhauler is in storage for the winter.
As bamfm7 said, I don't really have any problems with the tranny hunting for gears. I tow a 5th toy hauler that tips in at around 15,000 lbs. Actually I don't consider that very much weight for this truck. I think the raw size of the 5th is as bad or worse than the weight. I also have a large dump trailer that when loaded tips in at 30,000 lbs or so. My truck has no issues pulling that around either. I do run stock sized tires and mine is a 4 x 4 which means it has 5.13 gears. I think most 4 x 4's have the 5.13 gears. That said it sure would be nice to be able to lock out 6th gear without jumping to 4th. GM just completely missed that on these trucks. When we are towing through the Adirondacks in upstate NY I don't need or want 6th gear but have no way to prevent it from going there.
 

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OK I havent been on here in a while and ran accross this post, I have an 07 kodiak 5 speed I want it to have 6 just like everyone else. My question is even though it sucks has anyone tried to get GM's authorization to do the flash? I dont tow very heavy around 10500 fully loaded and with the 70mph speed limits on the interstate I could use another gear. So please fill me in on any new info I am going to see an allison dealer Monday but sure I will get the same story. I would be happy with leaving my shifter just the way it is cause I have no need to manually shift it into 1st any way, would I have any problem with that?
 

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Thlught i'd revive an old thread!
I contacted my local dealer about reprogramming my tcm to make it a 6-speed and this is the response I recieved:
"Not sure if you received a response from my service dept but, they have to change valve body in the transmission to give it sixth gear and then do the reprogram. So there are some parts required. "

I sent in my vin with the request and had to wait a while for a response as well. Using the picture I have here can anyone see any reason why the flash wouldn't work on my tranmission? Looks the same as bamfm7's to me so I think it should work.
Just feels like the dealer is giving me a generic response!

 

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im about to do this mod as well so interested in what others have to say
 

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Discussion Starter #18
OK I havent been on here in a while and ran accross this post, I have an 07 kodiak 5 speed I want it to have 6 just like everyone else. My question is even though it sucks has anyone tried to get GM's authorization to do the flash? I dont tow very heavy around 10500 fully loaded and with the 70mph speed limits on the interstate I could use another gear. So please fill me in on any new info I am going to see an allison dealer Monday but sure I will get the same story. I would be happy with leaving my shifter just the way it is cause I have no need to manually shift it into 1st any way, would I have any problem with that?
If I were you, I would stay away from the allison dealer They quoted me $250 and I still had to have the letter BS. It cost $60 at the chevy dealer.


mcmax20- You should be able to do a flash to get 6th

cablackone- You will be able to manually shift into 1st. You wont be able to manually select 5th. if the trans is in 6th and you hit tturn off OD it will shift into 4th. 6th gear is awesome after puttin some miles on it seems to shift fine on its own.....no need to manually control it.
 

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Here's the followup response I recieved, good for a laugh at best:
"This transmission is a 2000 series the cost to do this, will require a harness for the tcm and ecm and rewire of existing components to work with the valve body.aprrox cost 2600.00 harness, ecm 2000.00 and gm to program [unknown if they can] to your vehicle, ecm needs to be aware of 6th gear,tcm 1500.00 with programing from waterous power systems if they will do it [legal rules], rewire existing harness in truck 2500.00 , transmision asy as they are wired differently 9000.00 , trans install 1250.00 total aprox 19.000.00 plus tax and programing cost unkown?"

The worst part is that this dealer (stealer!) is the only offical GM medium duty dealer in my area, looks like i'l have to go in and hold their hand to get it done. Frustrating!
 

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LMAO....gotta love that....Occasionally you will find a person who works at a dealership to have a brain and actually want to help and listen, but from what Ive found, the majority are people who have ZERO common sense, only know how to read the manual and send funny jokes to their co-worker in the next office. I CAN NOT STAND dealers.....just my two cents :)
 
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