4.30 from 3.73... will I accelerate quicker?

[Suprapowaz!(2)]

I currently have stock 3.73 Lsd. If I were to swap to a 4.30 will I go quicker in the 1/4? My plan was to get a hold of a 4.30 and prep it for dragstrip use. I'd abuse that diff until it gave out. I would keep my 3.73 for back up just in case. So will I notice any gains, or is it not worth the effort?

 

[IJ.]

Off boost will be better, on boost it won't load the turbo enough and you may not hit full boost in the lower gears.

 

[Dylan JZ]

Get a 3.91

 

[Suprapowaz!(2)]

Off boost will be better, on boost it won't load the turbo enough and you may not hit full boost in the lower gears.

I could use some more pick me up off boost. I don't hit full boost in first gear with 3.73's, but I do in second. Is there a chance of 4.30's slowing me down in the 1/4 due to the turbo not loading up in the lower gears? Or will getting off the line quicker cause of the higher gears make up for it? I guess there's only one way to find out.

 

[IJ.]

My "guess" would be it will be slower over the 1/4, I ran 4.10 in mine after trying the 4.30's but I had the Tremec TKO Trans so a fairly tall OD.

When I swapped to an Auto it was quicker again with the Tall 1st gear and 4.11's in the IRS 9", then swapped to 3.50 finally ending up at 3.0 with the Turbo 6.0L

 

[Suprapowaz!(2)]

Maybe I should skip the 4.30 swap and just do a turbo 6.0L. That'll make my car quicker, yeah? On a side note, if this 7m goes out on me I will be looking into an LQ4 or LQ9 as a replacement.

I'm still curious as to how it would run with the higher gear. Maybe I'll get it, swap it in, do a little racing and find out. If I don't like it then I could always sell it. There's always a member or two here looking for one.

 

[IJ.]

Yep would be worth the effort just to get some real world data, a buddy with another car and some tools so you can swap pumpkins you could do back to back testing on the same day

 

[Suprapowaz!(2)]

That's sounds like a good idea. Looks like that'll be my next project. I'll start a post on it when I get closer to doing it.

 

[IJ.]

Cool will look forward to it as my testing was all seat of the pants stuff, I was around the 550rwhp at that stage so very traction limited on street tires.

 

[Suprapowaz!(2)]

I've never dynoed my car, but I'd guesstimate that I'm putting down 310-320rwhp right now. Car runs 12.90's as of now with the 3.73's. We'll see how it goes. I'm going to pick up this 4.30lsd sometime this week. I'm not going to put any money into it right now, just swap it over with new fluid and hope that I don't hear any unusual noises coming from it. I'll take a friend out to the track and make some runs with both rears and see if there's a difference. It's going to be a few weeks before all of this will take place, but I will post it.

 

[toyotanos]

My experience has been going more aggressive rear end (4.30) lost me a bunch of traction.
Last year with the 3.73 I ran 11's but once the 4.30 went in the traction dropped off hard. Once the boost came up the tires didn't have the traction to hold it.

I was at 564 last year and it will undoubtedly be higher this year so I'll need all the traction I can get!


Setup was 26x10.5x15 MT ET street bias plys (admittedly ~4 years old)

 

[kaiser]

Hypothetical question, what if the tires were up sized to compensate. I just finished swapping a 7M into a Pickup with 5.29's on 35" Tires. Still buttoning up some wiring and exhaust issues. But will this setup hinder my from reaching full boost? Or will the big wheels load the engine enough?

 

[kaiser]

Bump!

 

[AbsoluteSpeed]

You need to figure out your effective gear ratio.
(Gear Ratio) x (Stock Tire Diameter/New Tire Diameter) = Effective Gear Ratio

Assuming you're using a 4.10:1 diff and the same transmission.
4.10 x (24.82"/35") = The same as using a 2.90:1 diff

So, this will provide plenty of load on the engine (maybe too much? idk).

 

[kaiser]

I am using R154 gears with an R150F Output shaft so I can retain 4x4 with a TCase.

My Axles are 5.29

So 5.29*(24.82"/35")= 3.75

Still enough load?

 

[Nick M]

Hypothetical question, what if the tires were up sized to compensate.

Then why bother with the changes if the overall ratio remains the same?

 

[Suprapowaz!(2)]

Sorry guys, it's a no go. I just came back from the junkyard. I dropped that 3rd member in no time. Took up front to pay for it and found out it was going to be $170 w/o warranty. I misread the price sheet and thought it was supposed to be $55. I'm not willing to pay that much for a questionable rear. Not to mention it would be hard to sell and recoup any money back at that price. I'll just stick with my stocker.

 

[S.A. supra]

What year was that car? What years have what gears?

 

[AbsoluteSpeed]

Info is easy to find, but i don't mind posting it for future reference

North American Differential Codes:

G284 = 4.30:1 4-pinion 8.0" pre-89 N/A Diff (no-LSD, USA Only)
G282 = 4.30:1 2-pinion 8.0" 89+ N/A Diff (no-LSD, USA Only)
G285 = 4.30:1 4-pinion 8.0" N/A Diff (with-LSD)
G315 = 3.91:1 4-pinion 8.0" pre-89 Turbo Diff (with-LSD)
G305 = 3.73:1 4-pinion 8.0" 89+ Turbo Diff (with-LSD)

 

[AbsoluteSpeed]

I am using R154 gears with an R150F Output shaft so I can retain 4x4 with a TCase.

My Axles are 5.29

So 5.29*(24.82"/35")= 3.75

Still enough load?

Yes, that is basically the equivalent of the longest gear available in the supra plus you have additional drivetrain loss because its 4x4.