1999 silverado 4.8 to 6.0 swap help, truth needed
 

Ok guys, been hearing several different thoughts on a 4.8 to 6.0 swap. Ok, my truck is a 1999 ecsb 4x4 with the 4.8, i want to swap in a 6.0, everyone said it will go right in, any model 6.0 from 1999-06 , no problems, direct swap, THEN, I hear i need to stay away from any 1999-2000 6.0's because they had longer cranks and wont work with my current and stock 4l60e trans, they said to get a 2001-06 6.0 and it would work, just use the 4.8 flexplate, ok, all good. WELL, now im hearing that because my truck is a 1999, that the crank in the original 4.8 is also long, just like the 1999-00 6.0's have, so my original 4.8 flexplate wont work on the 6.0 to use my tranny. so, anyone here ever done the 4.8 to 6.0 swap ON a 1999 truck? If so, whats the truth and what do i need to make it work? remember, i want to keep my stock original 4l60e trans that is in the truck mated to the 4.8 (yes i will build the tranny to hold up to the 6.0)

SO, Truck is a 1999, original 4.8, 4l60e
was told to get 2001-06 6.0 and use my 4.8 flexplate on the 6.0 to use my tranny,
then heard that wont work because my 4.8 is a 1999 model and uses a longer crank, therefore, that flexplate wont work to mate the 6.0 to my trans.....?
So, if my truck were a say, 2003 with 4.8 and 4l60e, then i could get a 6.0 from 2001-06 and slap it right in, but, because its a 1999 that came with a longer crank in the engine, the trans in the truck wont work with the 6.0 because the flexplate..
HELP!!

I've never heard of long crank 4.8

Who told you that?

Moved this to the General discussion for you. You might get more response in there with this type of question.

Use the search feature at the top as this topic has been covered several times.

There has NEVER been a long crank 4.8 with a 4L60E.

01-07 Classic LQ4 will bolt right up using existing 4.8 flexplate.
03-07 Classic LQ9 will bolt right up using existing 4.8 flexplate.

99-00 LQ4 had the long crank with Iron heads.

The truck will run but you will need to have the computer re-tuned. The calibrations for the engines are different.

Like they said above. Good luck with your swap.

I've heard of the 4.8 having a longer crank with the 5speed in the early models. But like you, ive just heard/read this and can't clarify. I would suggest buying a 6.0/80E and swapping that in at once and not worrying with the 60e and a long cranked 4.8

Correct, the 1999 & 2000 model 4.8L engines mated to a manual trans were the only long style crank Gen III engines outside of the same year model 6.0L's.

really want to keep the 4l60e, buddy at work builds them strong enough for the 6.0

so they actually made 2 different cranks for the 4.8, one for the automatic and one for the 5 speed?

Sounds like since you already have an automatic truck a post-2000 6.0 will work just fine for you.
I swapped a 2000 4.8 out for a 2003 6.0 keeping my original transmission and everything else and it worked just fine. Like already mentioned above you'll need a new tune to make it run right.

awesome! what about mileage, will the 6.0 do better than the 4.8 in my application since the power to weight ratio will be better (its an extended cab shortbed and 4x4)? I know the 5.3 does better fuel mileage than the 4.8 in the bigger heavier trucks like this.. 6.0 will remain stock, just a custom tune..

Mileage stayed the same (17-19 mpg) with 4x4. Swapped in a 6.2 later with a 6L80E/AWD and it still stayed the same. Hard to drive a 400+hp RCSB like a sane person though :)

Good Info!!!

I have heard that but have never seen one my self.

I just wanted to make sure people knew that it was NEVER mated to the 4L60E

The wide flange 4.8L crankshaft was casting number 12553312, while the narrow flange crank had a casting number of 12553482. The wide flange 6.0L had a casting number of 12552215, whereas all the other Gen III engines had a narrow flange crank with a casting number of 12552216. Even with all the different displacement engines having the same casting number crankshaft, this doesn’t mean the crank can just be pulled from one engine and installed in another, as they were individually balanced and the car engines even had gun drilled crank, so re-balancing would be prudent.

getting more and more excited about this swap. Only sucky thing is that i could get a 5.3 for half the price of a 6.0 though..

Sounds like what you need is a 5.3 with a turbo ;)

Why even go through the trouble of a 5.3 swap? The 4.8T seems to be a proven setup..When I buy my GMT900 rcsb I will turbo it and avoid ALL the other headaches..

not swapping till the 4.8 is worn out, just planning ahead and figured since its a direct swap, might as well go a little bigger, no turbos or anything..

Just said it to be funny. 4.8T does seem to be a proven setup. I probably wouldn't do the swap either if I was going with a turbo.

The 6.0's make a bunch more torque stock for stock.

5.3's around me are gettin cheaper and cheaper. i've found 10 within an hr drive of me for $450 or less, complete engines. 6.0's are $1200 or more. If it were me and i had a 4.8 i would keep it, buy a spare 5.3, maybe 2, and then full bolt on's and some sort of FI or sweet nitrous setup. I think i would only get a 6.0 if i could find one on the cheap.

i keep hearing about a bad batch of heads called castechs? What year engines were they on so i can avoid getting an engine of that year..?

706 casting 99 up gen 3 heads. Not all of the 706 heads were castech though. If you do a search someone posted about what the casting mark looks like and where it is to id a castech vs non. Hope this helps

99-up, all the way to 2006? man, that sucks because was looking at engines on e-bay because there are non around here, so i would be taking a big chance not being able to look at the heads, crap!

The 5.4 in my Suburban has a LS1 gun drilled crank, over 10k miles so far and no problems or vibration.

All you need to do is ask them to look at the 3 digits cast on the outside. 706 and 862 are the ones that would apply to 4.8/5.3L some of the later engines got a 799 casting which is identical to the 243 heads.

I said prudent, not that it wouldn’t work. Anytime rotating assembly components are swapped from one engine to another, balance should be checked. Just because in one case it worked out doesn’t mean I would go around recommending it. However in the case with the gun drilled vs solid cranks the metal being removed from the centerline, it doesn't have as great of an effect as it would if the metal was removed from one of the rod throws or counter-weights.

Well Said!!! :judge:

My comment was not argumentative, simply stating that for a mild engine in a daily driver the crank difference is not a big deal.

I understand, but so many people do misunderstand others statements and would turn it into something it’s not meant to be and we all know how assumptions go. I read it on such and such and next thing you know it’s the gospel.

As mentioned "in general" it is a good idea to have it checked for balance for your application. It may work just fine, but the weight of say a 5.3 piston and rod is different from say that of a 6.0L.

No harm no foul

ok, so if i ask them to look at the head number and they say its 706 or 862 i should leave it alone because they are the bad one that crack?

So I've got a 4.8L 1999 rcsb mated to a manual transmission and I'm planning a 6.0L swap. Will I need the 6.0 w/ a longer crank or will it matter?

All 6.0s are made to accept your 5speed trans. Its the 2001up 6.0's that have the option to use a 4l60e easily.

I got a 04 chevy Silverado with4.8 computer and my 6.0 works fine on the computer. and also it got plenty of power. Wasn't really that hard.. had to change fuel rails and spark plugs.. also mass airflow senor had to be changed

Lets climb aboard Ginger Billy's time machine and travel back in time 9 years.... OP are you still with us... hello?

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(granted this misinformation was also from 7-8yrs ago) according to what i've always heard in addition to what's posted above, he actually WOULD'VE needed a 99-00 6.0L with the longer crank to directly swap... or if using an 01+ LQ4/9, he'd've had to also get a different flywheel made for the short crank engines. that's because the 99-00 LQ4s and the 99-00 LR4s mated to NV3500s had longer crankshafts with flywheels & flexplates that accommodated the difference.

yes, you just retune the same computer, and you'll be fine. swapping to different PCMs is primarily a factor with the 1999 v6s (maybe some 2000s) that still used the black SBC computers.

oh, don't be so ANAL about it! :jest:

I need help too putting a 6.0 w/4l80e into a 90 gmc Sierra 5.7/700r total conversion to drive by wire

well that problem, good sir, is a topic for a different section and/or forum.
if you dig around, you'll find plenty of places that detail how to LS swap a GMT400 truck... but this one here's about trading short blocks in a GMT800 (which is WAY more straightforward).