5 speed to 6 speed conversion.

Frogman1

FROGMAN1
Aug 5, 2017
31
1
8
VA Beach
Thanks Mike. I have no plans of messing with the defuel. Initially when I posted on the thread I was only seeing the last 3 pages. Today I got all 10 pages and was able to get answers to the first 3 questions from the earlier pages. I'll give Duramax Tuner a call and see if there will be any complications when using the PPE or other tuner programs on their locked TCM. It's been a year. Maybe they've found a way to hide their tunes but allow for adjustments.
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
19,366
1,920
113
Phoenix Az
You can’t put a transgo jr in your truck anyhow, you need the updated c2 apply piston which requires pulling the trans.

And 06+ can’t “hold” 500hp. some will, some won’t. Been in enough of them that start slipping converters at even below 500hp
 

Max Attitude

11SIX
Mar 7, 2012
814
0
16
Caledonia, MI
You can’t put a transgo jr in your truck anyhow, you need the updated c2 apply piston which requires pulling the trans.

And 06+ can’t “hold” 500hp. some will, some won’t. Been in enough of them that start slipping converters at even below 500hp

Cool, thanks! Thats why I put it in quotes, ha
 

THEFERMANATOR

LEGALLY INSANE
Feb 16, 2009
3,887
38
48
41
ZEPHYRHILLS, FL
You can’t put a transgo jr in your truck anyhow, you need the updated c2 apply piston which requires pulling the trans.

And 06+ can’t “hold” 500hp. some will, some won’t. Been in enough of them that start slipping converters at even below 500hp

You can put a Jr in, it just isnt going to help the C2's which is the weak link.
 

TheBac

Why do I keep doing this?
Staff member
Apr 19, 2008
14,316
529
113
Mid Michigan
Since I have absolutely no clue as to why, can you expand on why you cant? Just for my own curiosity, b/c I dont think Ive ever read anything about it.
 

Bdsankey

Vendor
Vendor/Sponsor
Feb 1, 2018
3,069
376
83
Neenah, Wisconsin
Sorry ferm, my post was in reference to what Evan I stating. Should have worded it better

So at that point how does someone build it to hold power, LML valve body mods?

I'm looking at building the trans in my LB7 and going to a 6spd since 90% of my driving is on the freeway at 70+.
 

2005_duramax_owner

New member
Apr 7, 2022
2
0
1
In November of 2021, I purchased Duramax Tuners 5 to 6 speed Allison conversion kit to install in my 2005 Chev 2500HD that I purchased new back in September, 2004. I have put about 2000 miles on the truck since I installed the kit back in Dec, 2021 when it had about 125,000 miles on it.

I would recommend to anybody who buys this kit to make sure that they have access to a TECH 2 scanner to calibrate the transmission after installing the valve body and the TCM. On the first shift into 6th gear, it felt like somebody had hit the side of the transmission with a sledge hammer as the shift was that hard. After doing some research, I found that the TECH 2 scanner has a calibration function for the Allison transmission. After following the instructions on the TECH 2 to calibrate the transmission, immediately the shifts, up or down through all of the gears were much nicer.

After driving the truck for awhile the shifts became very good whether I have the transmission in T/H mode while towing something or just during normal driving with nothing behind the truck. I think the shifts with the new TCM and valve body are better than what they were with the old TCM and valve body that were in the truck.

I bought this kit specifically to drop the RPMs while driving at 70 to 80 mph in order to quiet the noise in the cab which it does making the driving experience a more positive one. And as a bonus, the calculated gas mileage has gone up about 1 mpg. As well, the pyrometer temperatures have dropped about 100 degrees while cruising at 75 mph due to the lower RPM that the engine is running.

My experience with Duramax Tuners has been a very positive. They gave me good support during the purchase and very good support after. From what I can see of the company, they are a good group of guys that want to deliver a good product at a decent price and are willing to back it up.

I am very impressed with the work that Duramax Tuners did in reworking the software in the TCM and rewiring the later model valve body to work with the LLY platform. There are some very smart people working inside that shop.
 

Mike L.

Got Sheep?
Staff member
Vendor/Sponsor
Aug 12, 2006
15,686
231
63
Fullerton CA
You sound like you work there. I tested the prototypes of that conversion and helped straighten out some flaws in it. It's still not impressive and will never hold any power. The trans starts dropping out of 6th gear under aggressive throttle and using T/H to cancell 6th gear has its own problems at about 50MPH. It will drop out of 5th to 4th causing an over reving. I do not recommend this kit. Actually, I don't recommend any of the 6 speed conversions.
 
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