3.23 or 3.42 with new Diff?
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Launching!
Joined: Jan 2016
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3.23 or 3.42 with new Diff? About to change the 10 bolt out for a Strange 12 bolt in my WS6....I have a Performabuilt 60E and FTI 9.5 Billet 3600 stall..Should I swap to 3.42 or leave it at stock? It mostly a DD car but will see some track as well...Has a LS3 in with TFS 255 heads...I cant remember where I seen the calc but I wrote the numbers down....stock gear at 80 has me at 2513 rpm, and 3.42 has me at 2660..Only a 147rpm diff...3.56 puts me at 2769 or 256rpm diff...95% of playing is from a roll or hwy speeds..Read a thread that if you have above a 3k stall lower gears wont make much of a difference in track time...
Changing 3.23s to 3.42s is a 6% imcrease in torque to the pavement. If the 10 bolt was being considered to change from 3.23 to 3.42,I agree with the previous post of not worth it. But considering a 12 bolt is being ordered and that gear set hasn't been specified yet,why not do a 3.42. drawback is the computer has to be re-progammed to 3.42 change.
Joined: Nov 2001
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From: Schiller Park, ILL Member: #317
I agree with @FirstYrLS1Z . Zero point in the cost or hassle of this swap if you weren't getting a new rear end anyway. The performance difference would be marginal even with a stock stall speed, but with a 3600 stall you would likely see only a microscopic change in ET if anything.
But in this case, since you're starting from scratch and ordering a whole new rear, the only universal downsides are needing to re-tune for the new ratio and the higher cruising rpms. Other things to consider, depending on the new ratio you choose, which might be specific to your setup:
- rpm/speed at the end of a run; will the new ratio put you at a less ideal rpm/gear as you cross the finish? And if so, do you have room to work with shift points or tire height to fix this?
- exhaust note at various steady-speed rpms; will the new ratio put you in an rpm range that's not audibly favorable for typical cruising speeds with your preferred exhaust system?
But in this case, since you're starting from scratch and ordering a whole new rear, the only universal downsides are needing to re-tune for the new ratio and the higher cruising rpms. Other things to consider, depending on the new ratio you choose, which might be specific to your setup:
- rpm/speed at the end of a run; will the new ratio put you at a less ideal rpm/gear as you cross the finish? And if so, do you have room to work with shift points or tire height to fix this?
- exhaust note at various steady-speed rpms; will the new ratio put you in an rpm range that's not audibly favorable for typical cruising speeds with your preferred exhaust system?
Thread Starter
Launching!
Joined: Jan 2016
Posts: 224
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Its going to have to be tuned any ways..went from a LS1 to a LS3 with heads, cam etc...So that's not really an issue. Its going to cost the same to go back with 3.23, 3.42, 3.56 etc...Would not consider the 3.73 as that would be too low of a gear for my running 80+ on the hwy all the time..Im really considering going with 3.56 as its only 103 rpm above the 3.42 and 242rpm above the stock 3.23..I forgot what the STR on convertor was but can look thru my emails from FTI and find out...
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3.73 is not to low. It puts you at about 2k rpm @ 60 mph in overdrive with a 26" tire. Be about 2700@ 80 mph
but this gets you to 145mph on a 26" tire in drive assuming you're gonna spin a h/c ls3 to 7k rpm at least. And if you don't spin it past 7k you did it wrong.
but this gets you to 145mph on a 26" tire in drive assuming you're gonna spin a h/c ls3 to 7k rpm at least. And if you don't spin it past 7k you did it wrong.
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Joined: Aug 2007
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From: Turnin' Wrenches Infractions: 005
In a properly stalled car you wont see an ET gain making small gear changes. It will feel a little better as it will rev quicker and pull better at lower rpms without downshifting.