02 LB7 Allison to ZF6 Conversion

idlandk

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Jun 9, 2020
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Hello all, this is my first post. I don't usually sign up for forums but I've been searching this topic for the past week trying to find all the information I can but I can't find much and I'm hoping someone will be able to point me in the right direction. I'm swapping in a ZF6 and I don't have any wiring diagrams, and I'm wondering if someone has them available for an 02 LB7 or knows the best manual or place to get them. I want to do the swap properly and remove the TCM and Allison harness and I know the following has to be added back along with flashing to a manual operating system:

1. VSS - I think this wiring should be pretty straight forward as its just 2 wires that run to the ECM
2. Back up Lamp - Again, this is 2 wires but I don't have the wiring diagram to know where they go. Assume it would be under hood fuse panel
3. Clutch Pedal Position switch - There's 6 pins and from what i understand 4 are used for a duramax but i don't have the diagram for the pins.
4. Cruise Control - If I remove the allison harness, does cruise control need to be added back, or would this be a separate system and wiring up the CPP would make cruise function normal?

My understanding is the above are the only harnesses that would need to be added back if you were to remove the allison TCM ad harness. Can anyone confirm and point me in the right direction to get the wiring sorted? Thank you!

Another side note if anyone knows. Is the firewall where the clutch pedal mounts the same on a ZF6 truck and an allison truck or is there additional thickness on the ZF6 trucks?
 

fl0w3n

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Jan 8, 2015
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I am not sure on the wiring questions, I’ve never done the swap. I do believe I’ve seen other people post that the firewalls are identical between trucks and there are knockouts where you need them.

assuming you have the trans already? Take care of that tail housing... I’m so over my ZF6 that the next time it breaks I’ll just get rid of it.
im not into Facebook but there is a group called ZF6 Only and you’ll find a bunch of answers there. I’d recommend joining the group, there’s way more action there than on here regarding ZF6
 

darkness

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Jul 15, 2009
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Don’t quote me but I’m pretty sure the firewall is the same. The firewall already has the dimple where you’ll need to drill. It’s where I drilled my 2004 for running wires and what not thru the firewall.
 

idlandk

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Jun 9, 2020
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Thanks for the feedback. I'll check facebook and keep checking back to here to see if i get any response. I have all the parts but the wiring. Just waiting to sort that out before i start taking the allison out. Also didn't know about the tailhousing. I'm guessing a good brace will prevent that from breaking.
 

fl0w3n

Member
Jan 8, 2015
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Thanks for the feedback. I'll check facebook and keep checking back to here to see if i get any response. I have all the parts but the wiring. Just waiting to sort that out before i start taking the allison out. Also didn't know about the tailhousing. I'm guessing a good brace will prevent that from breaking.
Yeah, do everything you can to save that tail housing. In fact, check that yours now isn't already cracked or already was repaired. Once it's gone, it's a nightmare trying to find a replacement. People pay $1k for just the tail housing by itself, and I wound up having to buy a complete full rebuilt trans just to get a replacement for mine. If I had to do it over again I'd consider getting a 2wd tail housing and doing a divorced transfer case setup.

A perfectly balanced driveshaft and u-joints is critical, maybe even more so than the brace.


Oh, and my avatar picture... that's my ZF6 with the tail housing completely sheared off haha
 

idlandk

New member
Jun 9, 2020
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Crazy. I double checked mine and there are no signs of any cracking on the tail housing. I also checked the ZF6 facebook page and someone asked how to do the wiring for the reverse switch and had no response so I don't think they're going to be much help with my questions.
 

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