DadsLeftovers
Newbie
What RPM at about 65?I went to 4.11s with 275/60R15s and 700R4 (.7:1 OD), gained 3/10ths of a second 0-60 and 1/4 mile. Cruising at 80 MPH at ~2800 RPM.
Edit: I went from 3.42s
Rear end gear ratios
- Thread starter Outlawborn
- Start date
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Somewhere around 2275 RPM. I took my RPM and speed (2800 & 80). Took your 65 divided by 80 = 0.8125 and multiplied that by 2800 = 2275 RPM.
stutaeng
I'm Awesome
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koolademan22
OBS Enthusiast
What size tires do you plan on running? I agree with you on the hill country backroads.
boy&hisdogs
I'm Awesome
4.88s, that's what I have... on 37s though!
But really, I was overly concerned about going "too low" and turning too high of RPMs on the highway I went from 3.42 and 33s to 4.88 and 37s, which went from sub-2000 rpms on the highway to 2200-2500. So far the motor seems to be handling it like it's nothing, but the truck pulls soo much better. Having more reduction in your axle helps take some of the pressure off your trans, especially when it quits having to hunt for gears like mine was.
With a stock sized tire 3.73 would be normal/average, so I definately wouldn't go lower than that. 4.10 would be a fun truck, though I don't know what your new engine likes to run at.
But really, I was overly concerned about going "too low" and turning too high of RPMs on the highway I went from 3.42 and 33s to 4.88 and 37s, which went from sub-2000 rpms on the highway to 2200-2500. So far the motor seems to be handling it like it's nothing, but the truck pulls soo much better. Having more reduction in your axle helps take some of the pressure off your trans, especially when it quits having to hunt for gears like mine was.
With a stock sized tire 3.73 would be normal/average, so I definately wouldn't go lower than that. 4.10 would be a fun truck, though I don't know what your new engine likes to run at.
L31MaxExpress
I'm Awesome
When I had 31.5" tall tires with the 9.5 SF, I had 5.13s and a 2,800ish rpm stall in my 4L85E. I was turning around 2,800 or so at 70 mph. Passing on a two lane road, just give it some throttle and did not even have to downshift. I still cruised 85-90 mph ALOT. SBC Vortec boats run 3,500-4,800 rpm all day long same block, crank, rods, pistons, heads, and valve train as a truck.
Jerryred94silvy
I'm Awesome
I’m running 275/60R15 on all four corners currently and plan to keep that size. Although reading enough of this thread has me considering the 4.10s now. I just don’t know if it’ll bow the tires off at every single little throttle input with that low of a gear. I’ll play around with that RPM calculator some more and see what I can see.
Where do you want it to perform? And what performance do you want?
Do you want a tire burner, or a lazy mile eater?
Do you want a tire burner, or a lazy mile eater?
Jerryred94silvy
I'm Awesome
A tire burner that also can cruise a hilly backroad without lugging in overdrive. The days of daily driving this truck on the highway are over lol.
