Drivetrain
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Joined: Feb 2020
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Drivetrain I have just now registered to participate on this forum, not much good with computers, not familiar with forum etiquette, just lookin for straight answers from folks that have been there done that. I am building 1938 Buick 40 on s10 frame, ls3 connect and cruise 525 hp 4 l70e Tran. Need to order rear ended from strange , what is the best street gear ratio. TnxThx
Welcome to LS1Tech! Repost the question over in our Gears And Axles section of the forum. Lots of traffic over there and plenty of smart folks. If you know what rear tire your gonna run, it’s easy to figure out the exact rpm you’ll be turning at what speed. The 4L70 is basically a beefed up version of the 4L60 and has a nice .70 overdrive. Nice choice for a cool cruiser sir.
Also need to let us know what your intended use for the car is ("street" - local cruise-ins? Extended highway time? Track occasionally?) and torque converter choice (stall speed).....those can both impact gear choice as well.
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Joined: Feb 2002
Posts: 426
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From: ohio
3.20 to 3.73 depends on how tall of a rear tire. Anything taller than 26” I would go with something like a 3.55 or 3.73. The 4l70 has a 3.06 first gear and .70 fourth. There are lots of gear to speed calculators online that will show you rpm per mph. If it’s cruising you are doing, I always will go lower numerically.
You can calculate vehicle speed based on engine rpm and rear end ratio here. It's the only calculator that I have found that has a tire size calculator on the same page, rather than simply asking for tire height. Set transmission OR overdrive ratio to 1:1 and the other to your OD ratio of .7. My only gripe is that it only outputs speed based on rpm/gearing, rather than allowing you to input speed + gear to find rpm or speed + rpm to find gear.
I'd personally stick with something close to 3.73 with that OD ratio and assuming you're not building a max-effort drag car.
I'd personally stick with something close to 3.73 with that OD ratio and assuming you're not building a max-effort drag car.
