Have you tried asking about the hesitation issues on pirate4x4? A lot of people over there put the LS3 in truggies, etc. and might know how to address this. Good luck, I am super jealous of your new setup!

 

Was this an Alpha already, or a 3.7? I've always heard you have to do lots of beefing up of the front suspension, so the upgrade wasn't suggested. Better to just buy an Alpha.

 

It was the gutless I5 which I have hated since I bought this hummer. There is not a great weight difference between the two engines since the LS3 is all aluminum block. It does feel a bit heavier in the front but I need new shocks anyway so I will get the best ones I can all around and I'm sure that will help. Any recommendation on best shocks for street use?

 

Why not install Alpha torsion bars?

The LH8 and LH9 are all aluminum also and GM put different torsion bars in Alphas for a reason. The extra weight of the all aluminum V8 vs the I5. Pretty cheap addition compared to the swap you just had done.

 

Good idea. I think I'll do that.

 

Which crate motor did you use? I did the 376/480 LS3 on my truck starting 2016 and Im still fixing tiny issues here and there but Im almost as good as what you would expect from a stock truck (reliable low problems etc...)

when it comes to gear dont go below 4.10s. At highway speed you can command lock at 40 mph and your rpms will be 1400 but the engine is strong enough to move it. Im running 35s and a LED bar on the roof (far from aerodynamic) and even though its cammed it still has enough torque to move it. If you still have tuning issues let me know I could send you my file and you could take a look at it. I used what GM provides for this engine and it ran 90% good off the bat. Had to tweek idle abit to stop stumbling issues esp with a/c

 

Thanks. I'd love that tune file to compare to mine. Mine is the 6.2 480 also. Do you have some pics and posts about it? As far as the gearing I think we bought 3.76 and it's actually in the shop now having those installed. Even after exchanging the radiator for an aftermarket one with thicker core I had overheating problems. I swear the problem is coming from the tranny pumping heat into the radiator so it now has an aftermarket tranny cooler. We can't see if it makes any difference until we get the gears in. When I did a "tuning run" slowly revving the engine up to below redline (about 5800) at different power settings trying to fill all the cells the think overheated again. I was only out driving around for 10 minutes and when I parked it was gurgling and tranny fluid was all over the place. We could find no leak so it must have come out the vent. It just seems like a lot of heat is being generated in the trans. I will limit my tuning drives to under 10 minutes from now on. When I get it back I'm hoping that all the overheating is solved. Summer will be a bitch if I can't get it running a lot cooler.

 

Dude I saw your videos and IMHO your cooling is wrongly done.
first, it seems you are running a spal 16" fan. Its great but not enough. The problem with the H3 is that the radiator is small. Even with a griffin rad that I have, which is two core, the surface area is the issue. An H3 has a 22.5" wide rad core, a 6 litre silverado has a 32" wide core and thats alot.
second, the h3 engine bay is a heat trap. It will keep as much heat as possible inside it. Try opening the hood in the summer and you will understand. Venting it is an option that you should consider.
Im running a dual puller fan setup plus a pusher fan and it still heats up. I am currently working on installing my dual fans on a shroud in order to pull from all over the rad which should help. At the moment, my 3 fans running will pull 110 amps which is alot of power....
As for the trans heating, I am running a standalone tru cool 40K cooler. Keeps my temp at bay even woth 125* ambients. My radiator is bypassed to eleminate the cross contamination that happens to built in trans coolers.
Btw, LS3s run in the 220 - 235 range. If you check the cooling fan logic of an ls3 you will find that fans are commanded on low speed at 220 and hi speed at 235.

finally, i have my trans shift points set for 6500. My trans is built though but it would be a shame to redline an ls3 at 5800 (ls3 should rev normally to 6600). I am currently abroad but i will send you my file for you to compare once I get back It works on my truck with 4.10 gearing and 35s. Hope it helps you out. Still have stalling issues when doing a quick 3 point U-turn or when giving it a quick load (like loading the engine to climb a curb and releasing the throttle immediately after doing it) but overall its great.

 

Further update: The trans lasted only 8k miles and is currently back to the shop that rebuilt it for a full rebuild. I'm pretty sure there is going to be no charge but it's unfortunate that I didn't get more mileage. When I get it back I'm going to "de-tune" in interest of extending the life of the trans. My best 0-60 time was 6.8 and that's where it's going to stand because I don't want to be replacing the tranny again. It was never designed to handle 480 hp and I guess I should have guessed that the transmission shop was promising more than they could deliver saying it would be able to handle it. I'm still very happy with the conversion and even de-tuned it will be way faster and better driving than the original I5 crap. If any are thinking of doing this conversion I'd recommend using one of the other LS3 variants that put out less power.

 

Its like looking in the mirror!!!

my original trans lasted 100 miles after the engine swap, had it rebuilt and it lasted 600 miles, rebuilt it again but with every upgrade part available, now it has 600 miles on it but my truck was down for over a month due to wiring issues