Jump to content
  • Sign up for FREE! Become a GM-Trucks.com Member Today!

    In 20 seconds you can become part of the worlds largest and oldest community discussing General Motors, Chevrolet and GMC branded pickups, crossovers, and SUVs. From buying research to owner support, join 1.5 MILLION GM Truck Enthusiasts every month who use GM-Trucks.com as a daily part of their ownership experience. 

Engine swap

Recommended Posts

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. 

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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




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
Link to comment
Share on other sites

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

Link to comment
Share on other sites

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?

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.