GMT800 Question: Going from a LQ4 Vortec to LBZ Duramax?

[CheemsK1500]

I know this is a square body place, but I figured it’s worth asking since a lot of you great people toy with other stuff too.

I currently have a 2004 Silverado 2500HD 4x4 with the 6.0/4L80e/NP263. It’s a good and pretty clean truck, but much of the drivetrain is getting some age and mileage on it. I recently acquired a 2007 “Classic” 2500HD (basically a 2006 built in the 2007 model year) that has some bad rust and dents but has a decent drivetrain that is a LBZ/Allison 1000/NP261XHD.

Both trucks are crew cab long beds, the Duramax is a LT trim and the Gas truck is a LS trim (the only difference I can see options wise between LS and LT is no power driver seat on the LT, and transfer case lever is on the floor instead of having buttons on the dash.)

Can I expect a basic plug and play experience, when putting the Duramax drivetrain and electronic bits in the gas truck? Or should I just scrap this idea before I make my life difficult?

 

[CalSgt]

Pictures!

IDK… the LBZ/Allison trucks are pretty desirable right now. So long as the frame isn’t rotten I would probably repair the body on the LBZ and sell the gas truck to cover the bulk of the cost.

Also… depending on the LBZ frame condition it may be easier to swap bodies than drivetrains. I assume the front suspension is a little different on the diesel to handle the weight.

I think the transfer case that goes with the Allison is different, so the donor would still need to be manually shifted unless there’s a retrofit from manual to electronic shift that will work with the factory dash buttons

Also there may be a difference in crossmembers between the 4L80 and Allison.

 

[Smtty58]

I don't know much about newer trucks, but the huge amount of wiring and computers involved would make me think it's not worth the effort. As far as plug and play, my first thought would be is the 07 dash a direct bolt-on to the 04? The 07 isn't much newer than the 04, so I wouldn't expect any big gains in reliability or longevity.

 

[CheemsK1500]

Pictures!

IDK… the LBZ/Allison trucks are pretty desirable right now. So long as the frame isn’t rotten I would probably repair the body on the LBZ and sell the gas truck to cover the bulk of the cost.

Also… depending on the LBZ frame condition it may be easier to swap bodies than drivetrains. I assume the front suspension is a little different on the diesel to handle the weight.

I think the transfer case that goes with the Allison is different, so the donor would still need to be manually shifted unless there’s a retrofit from manual to electronic shift that will work with the factory dash buttons

Also there may be a difference in crossmembers between the 4L80 and Allison.

I may grab some pics later. I’ve considered just selling the gasser, but the overall condition of the diesel truck is pretty dang bad. Trashed front seats, mouse infested interior, a lot of the plastic bits are cracked, damaged or missing. None of the power windows or locks work on it at the moment. Long story short, the drivetrain and maybe the back seat are the only redeeming qualities the Duramax truck has.

A body swap is a solid maybe that might be explored, as for the transfer case situation, I’d just cut a hole in the floor of the gas truck and ditch the push button wiring and module. I’ve had it break before and never really liked it anyway.

 

[HotWheelsBurban]

I don't know much about newer trucks, but the huge amount of wiring and computers involved would make me think it's not worth the effort. As far as plug and play, my first thought would be is the 07 dash a direct bolt-on to the 04? The 07 isn't much newer than the 04, so I wouldn't expect any big gains in reliability or longevity.

Sounds like an interesting project.....
Might wanna mosey on over to www.gmt800.com
This is a forum group for those era trucks, I know some of the guys over there and they have lots of expertise with these models. It's run by the same people who run this one and the GMT 400 group.

 

[TotalyHucked]

I'm pretty well versed in these trucks but can't say I've ever run into anyone doing a diesel swap into a gas truck. I know for a fact they changed all the wiring to a canbus style system for '03-up. The wiring style should be the same, but I'd be willing to bet between the drivetrain and transfer case differences, that the body harness and dash harness are different. Personally, I wouldn't bother. I'd sell the LBZ truck, somebody will buy it for the drivetrain, and either freshen up your 6.0 drivetrain or sell that one too and buy an LBZ that's ready to go

 

[CheemsK1500]

I'm pretty well versed in these trucks but can't say I've ever run into anyone doing a diesel swap into a gas truck. I know for a fact they changed all the wiring to a canbus style system for '03-up. The wiring style should be the same, but I'd be willing to bet between the drivetrain and transfer case differences, that the body harness and dash harness are different. Personally, I wouldn't bother. I'd sell the LBZ truck, somebody will buy it for the drivetrain, and either freshen up your 6.0 drivetrain or sell that one too and buy an LBZ that's ready to go

I’m starting to entertain this idea. If my gas drivetrain suffers some sort of catastrophic failure in the near future, maybe I’ll consider turning into a diesel with the available donor truck, but for now it’s pretty problem free, except for that annoying exhaust manifold leak, but hey, that’s just an excuse to install headers….

 

[Bextreme04]

I’m starting to entertain this idea. If my gas drivetrain suffers some sort of catastrophic failure in the near future, maybe I’ll consider turning into a diesel with the available donor truck, but for now it’s pretty problem free, except for that annoying exhaust manifold leak, but hey, that’s just an excuse to install headers….

There's a guy here in Vancouver, WA that does these conversions for a living. He buys decent used Suburbans and then goes to auctions and buys destroyed salvaged diesel trucks and swaps the drivetrain over. He said it is all plug and play and only takes him about 2 days to do a conversion. This was before Covid though...

 

[TotalyHucked]

There's a guy here in Vancouver, WA that does these conversions for a living. He buys decent used Suburbans and then goes to auctions and buys destroyed salvaged diesel trucks and swaps the drivetrain over. He said it is all plug and play and only takes him about 2 days to do a conversion. This was before Covid though...

Interesting. Maybe the main harness is all the same and just has pig tails for each version of anything. After thinking further, I guess that would make sense since you can plug and play the DL3 mirrors with turn signals in them on any truck or a 2500hd cluster into a 1500 and you get a trans temp gauge

 

[CheemsK1500]

Interesting. Maybe the main harness is all the same and just has pig tails for each version of anything. After thinking further, I guess that would make sense since you can plug and play the DL3 mirrors with turn signals in them on any truck or a 2500hd cluster into a 1500 and you get a trans temp gauge

For what it’s worth the relay/fuse locations for a lot of stuff under the hood of both the gas and diesel truck I have, are damn near identical. GM did a pretty decent job of making these trucks reasonably modular, especially if you don’t try to mix and match 99-02 stuff with 03-06/07 Classic stuff, but even that could be made to work with enough patience and commitment.

 

[Grit dog]

^ Was gonna say this.
Depending on your abilities, a Duramax swap into a gasser truck is definitely achievable. However just becuase the guy who’s done hundreds of them only takes 3 days (with a crew of mechanics I’m sure) doesn’t mean it didn’t take him a month to do the first one by himself or that you won’t spend hundreds of hours.
IMO that is the only remotely plausible scenario with what you got.
But idk how you could know the drivetrain is good unless you pack some miles on it first.
Your low buck Duraswap won’t be worth a schitt if it needs a transmission in 2 months, injectors and a CP3.
This is something that has a great chance of costing you a pretty penny and the “new” truck won’t be worth anything even if you get it done and operating properly because no one will want a backyard conversion unless they are getting a screaming deal too.
Take it fwiw, from someone who could do it but has enough sense not to, if the Dmax runs drives shifts great, you’re better off parting it out, (gotta assume you paid peanuts or your upside down already), pooling the funds from the part out and selling your current truck and buy a clean high mileage Dmax. JMO
IMO with old vehicles you’re always best starting off with something that has been cared for, maintained and driven regularly than a rusty rolling mouse house of unknown mechanical maintenance or condition.
On the contrary if this is just a hobby you want to do with no expectations of financial gain or value then sounds like fun!

 

[TotalyHucked]

^I agree with Todd 100%. Especially the way my luck goes

 

[CheemsK1500]

^ Was gonna say this.
Depending on your abilities, a Duramax swap into a gasser truck is definitely achievable. However just becuase the guy who’s done hundreds of them only takes 3 days (with a crew of mechanics I’m sure) doesn’t mean it didn’t take him a month to do the first one by himself or that you won’t spend hundreds of hours.
IMO that is the only remotely plausible scenario with what you got.
But idk how you could know the drivetrain is good unless you pack some miles on it first.
Your low buck Duraswap won’t be worth a schitt if it needs a transmission in 2 months, injectors and a CP3.
This is something that has a great chance of costing you a pretty penny and the “new” truck won’t be worth anything even if you get it done and operating properly because no one will want a backyard conversion unless they are getting a screaming deal too.
Take it fwiw, from someone who could do it but has enough sense not to, if the Dmax runs drives shifts great, you’re better off parting it out, (gotta assume you paid peanuts or your upside down already), pooling the funds from the part out and selling your current truck and buy a clean high mileage Dmax. JMO
IMO with old vehicles you’re always best starting off with something that has been cared for, maintained and driven regularly than a rusty rolling mouse house of unknown mechanical maintenance or condition.
On the contrary if this is just a hobby you want to do with no expectations of financial gain or value then sounds like fun!

Those thoughts crossed my mind too. I don’t exactly expect the Duramax drivetrain to be ready for “hard use” as it sits, since I have no idea what its service history was like. The only “justification” I can think of to put it in other than just having a good time, is that if both the gas drivetrain and diesel drivetrain are in similar condition, I’ll have to overhaul either of them eventually anyway, no matter what was in the truck. The gas drivetrain has the advantage of substantially cheaper parts and the fact that it’s already in the truck. I don’t exactly have much invested in the Duramax truck and no one is getting rich selling a high mileage gasser. The longer I think about this, the more I’m tempted just to part the thing out or assign it to permanent farm duty until it finally gets put out of its misery.

 

[legopnuematic]

Some insight here maybe?

If the frame is good on the Dmax, I’d think a body swap would be the path of least resistance if you were to pursue this. The rear in the diesel should be an 11.5” vs the 10.5” in the gas truck.

 

[Bextreme04]

It's clearly doable... what I'm noticing though is these guys start with a 3/4 ton SUV. I bet starting with a 1/2 ton makes it much tougher.
https://duramaxsuv.com/
https://www.dieselplace.com/threads....820026/?utm_source=google&utm_medium=organic

There's several companies that do it for government agencies only... Predator and Duraburb are big ones that come to mind.