Rear end gearing

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Do the math.

Let's not pretend like far less efficient engines weren't pushed harder 60 years ago with 1:1 3rd/4th gears and 4.XX gears on 26" tall tires. We called them muscle cars, they were envied, and drivers weren't wussies. LS ain't care about your 3500rpm cruise speed.
I’m not picking up what you’re laying down here.

A 4.11 or 4.56 will need a full manual valve body so he can leave in 2nd gear. I’d not recommend that. It is would be cheaper and more user friendly imo to put in a mid 3.__ something ratio.
 
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With your 28" tall tire and the 4L80's final drive of .75:1 and 4.11 gears my calculator indicates that with a highway speed of 70mph would be @ 2650 RPM. Having said that, is your converter a lock type? If not I would imagine your highway RPM to more like 2900 to 3000.
 
The link to that converter indicates it's a lockup converter. That is a good price for a 4L80 billet converter. I'm very curious as to how it works out.

What are you using for engine management/ecm?
 

200-4R:
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4L80E:

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and old muscle cars:

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I don't see the problem here?
 

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200-4R:
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4L80E:

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and old muscle cars:

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I don't see the problem here?
I'm just concerned about the turbo. They like load so I didn't know if it's gonna be okay with 4.11s
 
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You're correct Mike, the car will drive at the given rpm's with a 28" tire at 70. At 75 with the 4.11's he'll be at 2800. Yes that will work, but why do it? It will be harder to launch (bad) , he'll be in OD at the end of a 1/4 (very bad), and it will run just fine at 22-2400 RPM'S on the highway.

The BTR stage 2 turbo cam is not a 'big' cam in old school standards. The LSA is more a 70's grocery getter LSA, and the ICL is around 111 IIRC, which is not old school 'big'. I'm saying that the motor will run easily at highway speeds below 2500 - why not use it if he needs the gears at the big end of the track and to help launch the car anyway?

Seeing that he already has quite a nice plan, i.e cam, converter, trans, turbo, then if he has a MPH goal for a 1/4, then that should dictate his gearing. I know I fubar'd with this and am living with what I have until the time comes. I know that I have to change gears only because of the speed at the line - my 3.73's are too low for me to get over 145mph. I think the OP will be in a similar situation. I know I'm going to have to decide to go to either a 3.55 or 3.31 (Ford) when the time comes. If the OP puts in the 4.11's, he'll be needing to change gearing the 1st time he can make a 17-20psi hit for the length of the track.
 
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My point is there are many factors at play here, many of which have not been thought through or discussed. I must have missed OPs goals... and complete build specs. Because the only question I am answering is will a turbo 5.3 backed by a 4L80E on 28" tall tires and 4.11 gears work on the street: Which is yes, and just fine.

Is it best suited for a 8 or 9 second car? Don't know. OP didn't state an exact combination or goals. So we are doing a speculative @*ss grab in the dark here (must be Friday). Just can he drive around on 4.11s and it will perform fine. Do a gear swap if you can afford it, and you have specific goals in mind. Optimize the combination.

The whole "turbo load" issue is relative to the application. Me? I am fine giving up some "load" off the line to protect my fragile rearend and transmission. One thing I am not worried about is going 7000+rpm through the traps with a junkyard engine... especially with a suitable cam.
 
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