Jump to content

Engine swap

emtnm
 Share

Recommended Posts

emtnm Enthusiast

emtnm

Posted
Posted

I know I might get some flack for this but here it goes. I am thinking about taking out my 8.1 and swapping it for a 5.3. Just wondering if the wiring, or computers need to be changed. I’m mainly considering doing this because of fuel mileage and needing to find an oil leak that might be causing the engine to knock really bad. Any info that can be provided would be greatly appreciated. 

shakenfake Senior Enthusiast

shakenfake

Posted
Posted

You do not want a 5.3 in a 2500 truck.

 

You would have to change the wiring. I believe that the 8.1 computer will work with a 5.3 but I cannot remember

emtnm Enthusiast

emtnm

Posted
  • Author
Posted (edited)

Why would going to the 5.3 be a bad idea? What about going to the 6.0?

Edited by emtnm
David89GMC Enthusiast

David89GMC

Posted
Posted

Why would an oil leak cause the engine to knock?

You won't like the 5.3 if you ever try to tow anything.

Just how can you justify the expense? How many YEARS of ga$ $aving$ will the 5.3 $$$wap have over just keeping the 8.1? That's an expensive swap.

If you're able to swap the 8.1 for a 5.3 and handle the technical issues, why can't you just coax more fuel mileage from the 8.1?

A smaller engine will have to work harder than a large engine, so the 5.3 mileage won't be nearly what you expect.

 

Get a good programmer and adjust the parameters until your 8.1 mileage gets better.

davester Senior Enthusiast

davester

Posted
Posted (edited)

Just to follow up with your original idea, you need the engine, transmission, transfer case, wiring harnesses at least for the engine, transmission, and to the bcm (unless you like diffing the wiring diagram and repinning/wiring stuff, ecm at least, custom fab a driveshaft, possibly the front one as well, instrument panel (it's programmed different between gas and diesel), if the two trucks have different option packages, that is more work to either transplant or get it going.

 

And that's it you transplant in the 6.0/4l80e

 

Edit:

 

Oh yeah, I believe the radiator, shrouds and metal piece (forget the name of it) that goes across the front of the truck holding the radiator are all different as well.

Edited by davester
shakenfake Senior Enthusiast

shakenfake

Posted
Posted

6.0 would be a great idea. I would do that. Skip the programmer though, you are not going to get any real mileage out of it.

 

@davester This is a gasser to gasser swap not a diesel to gasser swap. Half that stuff you just brought up does not need to be touched at all lol

davester Senior Enthusiast

davester

Posted
Posted

ok, you don't need to do the engine harness, bcm, ip.  Still need to change all the driveline parts, and rewiring the transmission harness.

emtnm Enthusiast

emtnm

Posted
  • Author
Posted
51 minutes ago, davester said:

ok, you don't need to do the engine harness, bcm, ip.  Still need to change all the driveline parts, and rewiring the transmission harness.

Are you talking all driveline part, ie: differentials and rear axle?

shakenfake Senior Enthusiast

shakenfake

Posted
Posted

You would only need to do that if it came with an Allison.

Also I don't think the original engine harness works with an LS. The 8.1 is not an LS and therefore has different connectors.

davester Senior Enthusiast

davester

Posted
Posted

The 8.1 comes with an Allison.  You don't need to replace the front/rear diff, but the driveshaft will be a different length and you probably would need some adapter u-joints.

davester Senior Enthusiast

davester

Posted
Posted

From brief googling, it should bolt up to the allison, so that would cut down a lot of work.  You'd have to sort out flexplate/starter/engine mounts and then clearance around the front of the engine (as the engine is a little shorter, you still want the fan in the shroud to pull air through the radiators).  And you may want to regear it as the 6.0 will be happier with 4.10's vs I think the 8.1 normally gets 3.73.

emtnm Enthusiast

emtnm

Posted
  • Author
Posted

Thank you all for your help. I will be coming back and asking more questions as the time for the swap comes near (if the wife actually lets me). 

shakenfake Senior Enthusiast

shakenfake

Posted
Posted
On 8/9/2022 at 9:39 PM, davester said:

The 8.1 comes with an Allison.  You don't need to replace the front/rear diff, but the driveshaft will be a different length and you probably would need some adapter u-joints.

Not all 8.1s came with an Allison. The did come with a 4L80 as well.

 

The Allison has it's own TCM, trying to tie that into the PCM may be tricky

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.

  • Forum Statistics

    250.3k
    Total Topics
    2.7m
    Total Posts

  • Member Statistics

    342,716
    Total Members
    8,960
    Most Online
    BDS my HD
    Newest Member
    BDS my HD
    Joined

  • Who's Online   0 Members, 0 Anonymous, 593 Guests (See full list)

    • There are no registered users currently online

  • Latest Articles

  • Posts

    • BDS my HD
      Brand new to this forum. Questions about re-gearing my 26’ HD

      By BDS my HD · Posted

      Hello hello looking forward to expanding my knowledge of the 2026 2500 HD that I just bought.   Truck has 3500 miles on it four-wheel-drive crew cab and I’m about to put a 6 1/2 inch BDS lift on it 18 x 10 -25 offset with 37’s   Already have the wheels and tires just waiting on the lift install in about three weeks   Question what surprises am I not gonna be happy with?  I’m not new to lifted trucks so I know that acceleration towing gas mileage all that is affected..   Question is those of you that have this truck this powertrain with a 10 speed Allison and have done the mods that I’m doing,,, how bad is it? Is that Allison constantly gonna be hunting for the right gear to go into? And what about towing, acceleration, fuel consumption as mentioned?    Lastly how come I can’t find any ring pinion gear set up for these axles and when could I expect to see them?   I apologize if there’s any typos I’m doing speech to text on my iPhone.    
    • linc45bn
      2013 2500HD 6.0L intermittent no crank no start

      By linc45bn · Posted

      I've got a 2013 2500 6.0L Flexfuel. Drove the truck earlier today with no issues. Went to run an errand tonight and noticed key fob wouldn't work. Figured battery was dead, so replaced fob batter. Still wasn't working. Grabbed my other set of keys with the other fob and that one wasn't working either. So I manually unlock truck and insert key. Interior lights come on, dashboard lights up, turn key and truck starts. Turn truck off, like a moron, and try starting again. This time no crank, no click, no nothing. Lights still come on and dash lights up, but now I'm getting a service 4wheel drive, service tire monitor, etc. Check voltage on battery and Im showing 12.2v. Throw my battery charger on it and give it 15 mins and try starting again. But still no crank no start. Decide maybe its a bad battery, run to autozone grab a new one and put it in. Same issue. Disconnect battery and let it sit for 15 mins. Try again and still nothing. I had managed to roll the windows down earlier as its a humid night, but now I can't get them to roll up. Power locks are also not working now. Then randomly I try the key again, and it fires right up. Immediately I roll up the windows as we have nothing but rain forecast this week. I shut it back off wait 30 seconds and start up again. Worked a 2nd time. So turn it off, start putting things back together. Try one more time, and back to no crank no start. And now the car alarm starts going off. Had to disconnect battery and leave it that way for the night as I don't think my neighbors would appreciate my alarm going off again tonight. Any thoughts or help would be appreciated. 
    • Grumpy Bear
      first oil change - 2026 2500HD gas

      By Grumpy Bear · Posted

      No one will care for you like you care for you. Do what you can for as long as you can. IMHO of course. 
    • Grumpy Bear
      Oil Consumption

      By Grumpy Bear · Posted

      How about them NICKS!!! 
    • Peoplemvr
      GMC 1500 Illuminated Front Grill Emblem REPLACEMENT.

      By Peoplemvr · Posted

      Hi there.  Long time lurker, first post.    i have read the previous posts regarding the water ingress problem with this emblem.  I bought my 1500 SLT the  summer of 2025 new and after reading the MANY problems with these emblems failing I decided to install one anyways.  As per a YouTube video, I sealed ( or tried to) this sign with silicone sealant around the outer perimeter joint and the holes that were already somewhat sealed on the rear plate of the emblem.  And installed the connector assembly using dielectric grease on the connectors. The installation looked great and worked well for about 4 months……then FAILURE.  Grrrrrr…… I live in the great white north and wash my truck weekly in an automatic car wash  to keep the salt off.  Let me tell you that removing the old, failed emblem is a whole different animal than removing the OEM individual letters without removing the grill assembly. Mainly because the illuminated logo is built differently than the original letters which  you can remove the red surface lettering with a knife or some kind of blade which gives access to the tabs which hold the logo onto the grill. So I had to essentially destroyed the old emblem to remove it. Doing so killed my chance of doing somekind of autopsy on the failed , old logo.  But there was plenty of water inside when I ripped it apart.  Prior to installing the new assembly I tried it with the old harness and it works fine.   Does anyone have any insight as to where the water is getting into this emblem? I intend to seal the new logo with slow curing epoxy this time around using a syringe.  I think this newer emblem may be an updated unit which I hope GM got the vendor to fix. It has an October 2025 date on it.    If this one  fails,  I am just going to revert back to the non-illuminated letters….AFTER PULLING THE GRILL.    Any thoughts on sealing with epoxy would be appreciated. Thx!   Doug  

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...