03 built 5 speed conversion to a 6 speed via OEM?

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Bob H

Jet pilot wanna-be trainer
Feb 21, 2015
43
0
6
Norfolk, VA
I know some of you will read the title and think you know what I'm asking, but I'm not asking how to put a 6 speed behind my LLY.
I'm swapping my LLY out for a LBZ and I have a stage 5 Suncoast built 5 speed trans that works great.
The trans I'll be getting with the motor/swap was a flood car,(not same truck as the engine) so getting reasonable deal on it. After cleaning obviously, I was going to swap valve bodies, PNDRL switches and wiring harnesses,(inside and out) and I'm not sure what else?
Questions: Any reason I can't do that and anything I am missing in "converting" my 5 speed to work as a 6 speed behind the LBZ?
Yes, the ECM and TCM will be from the LBZ along with all the other wiring.

Main question - can it be done and any reason I shouldn't?
 
J

JRein

Aircraft Mechanic's Hero
Sep 26, 2015
212
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16
LRAFB, Arkansas
Take it easy on him. He's a naval officer and they haven't been doing too hot. At least in the Pacific anyways.

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B

Bob H

Jet pilot wanna-be trainer
Feb 21, 2015
43
0
6
Norfolk, VA
Hey - In my defense, all my previous searches turned up folks trying to put a 6 speed behind a LB7 or LLY which is a no-go and I'm fully aware of that.

And I did finally just find my answer - from Mike no less,(and really Ben right after him):
http://www.duramaxdiesels.com/forum/showthread.php?t=46772&highlight=speed+conversion

But in short - This will be a LBZ setup, I just don't want to waste my time/money spent on my existing built 5 speed if I don't have to. Appears I can use my 5 speed as the base.
 
B

Bob H

Jet pilot wanna-be trainer
Feb 21, 2015
43
0
6
Norfolk, VA
Copy on the water inside the trans issue. Just want to know if physical parts work as I didn't intend to just swap it straight over and I see how that could be read-into my response - but even a thorough cleaning and solenoid replacement may not be enough.
The important part - I wanted to ID what parts had to be swapped. From the post linked, ben said:
"To make a 5-speed trans work with a 6-speed TCM (an actual factory 6-speed TCM), you'll need a factory 6-speed valve body, the 6-speed internal NSBU (technically called an IMS), and the 6-speed valve body wiring harness."
And Mikes comment before that one:
"Swap the valve body, internal harness, shift shaft and internal linkage and mode switch."

I'd rather not chase my tail when its installed back in the truck. I'm comfortable with custom/details required to make the swap work, but don't pretend to know it all and appreciate the thoughts/feedback.
 
PureHybrid

PureHybrid

Isuzu Shakes IT
Feb 15, 2012
3,330
365
83
Central OH
Bob H said:
I may not know much about this - but I am nearly 100% certain that is not correct at all.
Click to expand...

Does the 6spd tcm not read the solenoids correctly??? Is it because of the nsbu??? The valve bodies might be different but there's no extra hardware to activate 6th gear, it's in the tcm.
 
C

Cougar281

Well-known member
Sep 11, 2006
1,755
214
63
St Louis, MO
PureHybrid said:
Does the 6spd tcm not read the solenoids correctly??? Is it because of the nsbu??? The valve bodies might be different but there's no extra hardware to activate 6th gear, it's in the tcm.
Click to expand...
The solenoids are different and behave differently (I think its an impedance difference). 5 speed TCM running 4th gen 6sp trim solenoids doesn't play nice (ask me how i know ;) ). I imagine 3rd gen 5sp solenoids would be equally unhappy with a 4th gen 6sp tcm. The solenoids are not interchangeable. And yes there is AT LEAST one hardware difference in the VB to allow the 6th gear. I'm sure you can find pictures of the two out on the interwebz ;).

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J

JRein

Aircraft Mechanic's Hero
Sep 26, 2015
212
0
16
LRAFB, Arkansas
5 speed
15eac6ec417da765cfa225c3cc8c8697.jpg


6 speed
4679c373c6f9c702a12e18c4e9cd4dce.jpg


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THEFERMANATOR

THEFERMANATOR

LEGALLY INSANE
Feb 16, 2009
3,890
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ZEPHYRHILLS, FL
And don't forget the f solenoid is completely different from 5 speed to 6 speed. 5 speed goes to 96% duty cycle at full lockup, 6 speed only goes to 67% at full lockup, and they do not interchange. You may also run into issues with your 03 base trans. Some 03's use the smaller cooler ports, and do not have the correct pump assembly for the g solenoid to function as that wasn't added until 04. Not sure what would happen if the g solenoid is commanded on without the correct hydraulic circuitry for it(but you could put a dummy solenoid in the pan to get around it).
 
C

Cougar281

Well-known member
Sep 11, 2006
1,755
214
63
St Louis, MO
THEFERMANATOR said:
And don't forget the f solenoid is completely different from 5 speed to 6 speed. 5 speed goes to 96% duty cycle at full lockup, 6 speed only goes to 67% at full lockup, and they do not interchange. You may also run into issues with your 03 base trans. Some 03's use the smaller cooler ports, and do not have the correct pump assembly for the g solenoid to function as that wasn't added until 04. Not sure what would happen if the g solenoid is commanded on without the correct hydraulic circuitry for it(but you could put a dummy solenoid in the pan to get around it).
Click to expand...
If he is swapping in a 4th gen 6sp VB, IMS and harness into his built 03 trans to go along with the LBZ ECM, TCM, engine/top end and harnesses (like i did with my 04, save the trans which was a 2006 that i built), which is really the only way to do it, thats all a non-issue.

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THEFERMANATOR

THEFERMANATOR

LEGALLY INSANE
Feb 16, 2009
3,890
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48
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ZEPHYRHILLS, FL
Cougar281 said:
If he is swapping in a 4th gen 6sp VB, IMS and harness into his built 03 trans to go along with the LBZ ECM, TCM, engine/top end and harnesses (like i did with my 04, save the trans which was a 2006 that i built), which is really the only way to do it, thats all a non-issue.

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Click to expand...

I wasn't sure about the different lockup boost valve. Up to 03 had the old style, 04+ has the one compatible with a g solenoid. It's been awhile since I looked at the hydraulic charts, and wasn't sure where the g solenoid would flow to when commanded on in an earlier trans with the different valve.
 
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