Alright boys and girls I have a lot of questions and would like to knock as many of them out in one post. I have a 2WD 2012 Silverado 5.3 with 3.42 gears. My plan is to swap in a L9H 6.2. I know these motors are extremely similar but was just curious if there are any minor things to look out for when performing the swap. I’ve done a couple of swaps in the past but it was always just replacing the motor with what was already in the vehicle. Also before dropping in the new motor I was planning on refreshing it a bit. I want to tear into the motor and clean and replace some things. Just curious what I could replace to extend the life of the motor and possibly make it run a little better. I want to add some performance as well without sacrificing much if any drivability. I drive roughly 25k-30k miles a year and occasionally tow with it. I’m keeping the stock cam without question but was just curious what else could be done outside of forced induction. I know basic bolt ons and good tune but was just curious if I could do anything else internally while supporting the stock cam. Also would it be worth the money to swap my 3.42 gears to 3.73 or just go for 4.10? Keep in mind how much I drive. Don’t really have a budget just want it all done right. Apologies for the the long post and thanks in advance!

 

This is just my opinion here so take it as that and an option for what you are doing.

If you want it to be simple as simple gets the straight swap is the easiest thing to do. It's not even worth it to open the engine up if it's a known good running engine. New gaskets and seals is a great idea still though.

I don't see where you'd gain much doing anything if you aren't actually swapping in performance parts. The biggest gains are in the tune in stock form, a decent tune on the 6.2 and the good transmission tune on that 6L80e will make it drive awesome. Going to 3.73 or 3.90's would be great too if you want to keep the highway rpm down. Though 4.10's might not raise it that much over the other two options. You can figure out engine rpm through various online calculators and you will need to know the final drive ratio of 6th gear for that.

 

 

Change the pick up tube o-ring and put the new one in right. Check the oil pump out. Dual valve springs?

I'd leave the 3.42 gears, you're already adding about 100 horsepower with the tuned L9H, it'll have plenty of power and not siphon off as many of the greenbacks in your wallet as it will with a lower ratio gear when you fill up.

 

Less gear does not mean better fuel economy... do the gear swap and enjoy the power.

 

I did this swap last summer. just added a cam.
it was a low mi eng. swap was a PNP. just need
to tune it after swap. see my sig for info on truck

 

Since when?

However, every engine has its most fuel efficient operating range. I had an LZ9 motor that got better mileage at 77 mph than at 70 mph and running it at 90 mph was only 2 mpg less than it's best at 77.

I wish my LC9 was like that!

 

Since the inception of the internal combustion engine. If it was we should all rock 2.56 gears lol. Running down the highway at some pathetic low rpm does nothing any justice but in a wind tunnel. The only good factory half ton set up is the max tow 3.73s and even then depending on tire choice it's probably too little.

 

with my 4L60 and 3:73 gears 26" tires
at 70mph = 2400/500 rpm's, I'm going to switch
to 27" tires this summer to drop the RPM'S
a little bit lower. 295x40x18 I need more
rubber on the ground anyway since the eng swap.