Do’s???? & don’t????

Brianmcelroy · December 18, 2024

I’m currently building out my 2015 z71 L83.
current mods: BTR stage 2 cam, rebuild heads; BTR pushrods, Manly valves, BTR valve springs, Chevy 12354 lifters, L86 6.2L intake manifold (none ported) Corsa cold air intake (closed box) speed engineering long tube headers, true dual exhaust 3”, 410 rear end gears.

what I need help with: stall & transmission, should I go with a built 4L80E or a built 4L90E? Or does anyone recommend anything better. I want a transmission that will hold about 600-700hp. This is a truck I’m driving daily. I take it to dinner and go cruise the city. I’ve always wanted to build a quick reliable truck that I can get in every day and drive. But I’ve seen where the stock 6L80E does not hold over 400hp very well. I also know if i I upgrade to a 6L90E that I will need to do a custom driveshaft which I’m okay with. I just want to know the most reliable way to go.
i know I have a z71. And I know I’ve lowered a 4x4. Some people will probably hate me lol but I want a fast in the city truck. And I like the launch on the 4 auto. ****** eats. But it’s also eating my gears too! Haha. Any recommendations help. Thanks guys.

Edited December 18, 2024 by Brianmcelroy

CamGTP · December 18, 2024

A 6l80e is plenty strong, they handle well over 500hp without an issue. If you want to abuse it, you need to upgrade it with some hard parts and better clutches. Swapping to a 6L90e is not an upgrade, it's going to handle the same power but with abuse it too will require better parts. Stuff breaks when you do stuff you shouldn't. If you do 6-2 power downshifts, stuff is going to grenade. Learn to roll into the throttle or use the tap up/down to select your gear if you plan the beat the ****** out of the truck.

A billet torque converter is a must in a 6L80e, the stock units are weak.

Going to a 4L80e is so much more work. How are you going to control it? What are you going to control the engine with now that it has no TCM communication?

The L86 intake upgrade is a good and bad. Swapping the throttle body is a hard part because tuning for that change is super complicated. It's not just a few changes for that. HP Tuners doesn't give you all the tables to change and only guys that have done user defined parameters and wrote their own custom changes to the software can really get it right. I always suggest keeping the L83 throttle body.

KARNUT · December 18, 2024

I’ve done modifications with most of my trucks. Usually S/C kits. All you needed was available and easy for a shade tree mechanic. Today if I was inclined I’d look for packages that dealers offer that was in your area. In my case there’s a Ford dealership that offers the Roush S/C kit with a warranty. No guessing done right with a warranty. You don’t even have to start with a new truck. You can even do it with a base model. While traveling through Georgia last year the local Ford dealership advertised a Roush converted package for 45K, truck included. Of course you can always do the I wonder how all this will work. Or go with a high horse power package no guessing with a warranty.

BraydenH · December 18, 2024

18 hours ago, CamGTP said:

A 6l80e is plenty strong, they handle well over 500hp without an issue. If you want to abuse it, you need to upgrade it with some hard parts and better clutches. Swapping to a 6L90e is not an upgrade, it's going to handle the same power but with abuse it too will require better parts. Stuff breaks when you do stuff you shouldn't. If you do 6-2 power downshifts, stuff is going to grenade. Learn to roll into the throttle or use the tap up/down to select your gear if you plan the beat the ****** out of the truck.

A billet torque converter is a must in a 6L80e, the stock units are weak.

Going to a 4L80e is so much more work. How are you going to control it? What are you going to control the engine with now that it has no TCM communication?

The L86 intake upgrade is a good and bad. Swapping the throttle body is a hard part because tuning for that change is super complicated. It's not just a few changes for that. HP Tuners doesn't give you all the tables to change and only guys that have done user defined parameters and wrote their own custom changes to the software can really get it right. I always suggest keeping the L83 throttle body.

Solid advice. I sure wish I’d have studied up a bit more before buying my 2014 z71 which is now in need of a new trans due to torque converter failure at 170k miles and I never even beat on my truck, I occasionally haul my 24’ work trailer across town or down the highway to the next town over but yea the 3rd gen torque converters and trans are absolutely weak points and at a price of 3-6g just for the trans