Take just the long block from the 4.8.

Bolt all your accessories off your truck onto it as well as the throttle body form you truck.

The only thing left then is the ecm. I know a ecm off a 4.8 will run a 5.3, but it just won't run it at full potential power. So I'd imagine the reverse is true in this case. It will run the 4.8, but will run it over what a 4.8 would normally be.

Whether or not that would be bad or not, I'm not sure, heck it might act like a tune, I've never tried it that way before, only 4.8 to 5.3.

 

What do you mean the long block? And where exactly is the pcm for these trucks? I could possibly get the pcm off the 4.8 truck as well

 

The long block is just the motor. So no accessories like the alternator, power steering pump, etc.

So just the engine block, heads, and intake.

The pcm is to the left of the battery under a black plastic cover in the engine bay.

The pcm off the 4.8 won't do any good really since it it's setup for a cable throttle body instead of your drive by wire.

 

So just take the motor anf the pcm with it and plug it all into my truck and shes good?

 

Nevermind the pcm in the 5.3 would run the throttle body so i would have to run mine id say..right?

 

That's what I'm thinking.

You could also probably find a pcm off of a truck 03-07c with a 4.8 and use that just so there's no questions if it will work or not.

 

Very few shops will pull a 5.3 engine and install a 4.8 engine. If you try it yourself, I believe you will find out why. At the very least you need to completely reprogram or replace the PCM. The days of just swapping an engine ended in the mid 90's. With enough money, it could be done, but if you have enough money to do it, you have enough money to buy a new crated 5.3.

Cf

 

I can get the PCM from the 4.8 im going to use but i would have to switch it to a DBC type throttle instead of DBW

 

It's not too hard of a job.

I helped swap a 5.3 in place of a hydro locked 4.8. Both were 1999 trucks. It took us a weekend starting Friday night and we finished Sunday afternoon. This was just with an engine hoist and regular tools done in a barn.

Everything bolted right up without a single issue. Everything plugged right in. The 4.8 pcm worked just fine. Only issue was the truck had seemingly less power than any other 5.3 truck. In fact, the owner of the truck said it felt just like his 4.8 did.

So it is possible the way of a "upgrade" (4.8 to 5.3) so I'd imagine that the same is true for 5.3 to 4.8. The only thing different in this case is the pcm and the throttle body, two things which are very easily over come, if needed to do at all.

 

Im hoping to just swap the DBW throttle body onto the 01 4.8 and plug everything in with my 5.3 pcm. I read this and it sounds like the 01 PCM may be programmed to operate dbw not sure though.>http://www.lt1swap.com/cable_conversion.htm

 

Fix the 5.3 oil leak!

 

^^^Exactly.

 

yea ive decided to fix the leak. But can i leave the t-case attached to the tranny when I pull them back out of the way to do the seal? I have never done this job before and im not 100% sure if I even have the tools to do it on my own. I dont have a lift or anything or air gun, or big money haha.

 

Leave the trans in, pull the engine and install a new short block.

200K is a dead engine IMOP.

 

You have to take the transfer case out separately then remove the transmission. It's not real hard, but it's not easy either. The cross member gets in the way so you can not take the transmission and transfer case out as one assembly.

 

Leave the trans in, pull the engine and install a new short block.

200K is a dead engine IMOP.

So, your advice is to replace the entire engine because it has 200k miles on it and needs a rear main seal?

 

You have to take the transfer case out separately then remove the transmission. It's not real hard, but it's not easy either. The cross member gets in the way so you can not take the transmission and transfer case out as one assembly.

This ^^^^

This ride needs WAY more then a simple seal. I can see that from my laptop !!

 

What is it you think you see exactly A496HD? The motor still runs awesome just leaks oil. The truck took a maine inspection sticker in December, and if you know anything it aint easy to get a sticker in the state of Maine. The truck does have a lot of miles on it and shes pretty beat but she still goes and 4x4 works just like new. I think its worth being fixxed anyways

 

These motors can last well past 200,000 miles, if you keep up maintenance on them.

 

Fix the seal. If worry about the motor otherwise, get a cheap compression tester and check it out. I sold a 01 Burb 5.3 243k mi., after I had the main seal replaced at 188k, did not use a drop of oil and ran really good. These motors are long life if it has been taken are of. My fishing partner's 02 4.8 has almost 300k on it and runs strong. Pulls his boat all over Texas fishing, almost every week.

 

+1 on checking compression before you start tearing stuff apart. My guess is if it runs good and no smoke, it should test out fine. Check compression in all cylinders, not just 1.

 

Why the long block? Might as well pull the short block and replace the pistons i think thats the only difference right? dished pistons on the 4.8 make up the difference in displacement over the 5.3L, he could take the short block swap his pistons out and go from there, especially if the engine is still good.

Have you done a compression check on your engine? it may be worth it just to fix the rear main seal.

 

The 5.3 has a longer stroke than the 4.8.

In fact, the 5.3 is basically a stroked 4.8. Some use the 4.8 flat top pistons on the 5.3 to up the compression a little bit

 

Ah yes, so in that case just do the opposite of my original post. swap the con rods instead of the pistons when you pull the short block.

you prob wanna fix your seal though, it wouild likely be easier.

 

Might want to do the crank too.