Gearing and tire sizes

Discussion in 'Engine/Drivetrain' started by 4lo4fun, Dec 22, 2020.

  1. 4lo4fun

    4lo4fun Enthusiast

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    So my 92 donor truck had 3.53 gears and my 78 has 4.10 gears. I'm looking for a charts or something to help me figure out what tire size I need to keep the speedometer reading correctly.

    I have been looking online, but everything I've found has been for off-road applications.
     
  2. jetas

    jetas Grand Toyotaholic

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  3. 4lo4fun

    4lo4fun Enthusiast

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    Thanks, bud!

    Between that site and a tire size converter, i found that 8 will need 255/55/r18 or 255/60/r17.

    Not super stoked about the increase in ride height, but what can you do.
     
  4. jetas

    jetas Grand Toyotaholic

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    Cant you just change out the gear on the speedo cable/sensor?
     
  5. 4lo4fun

    4lo4fun Enthusiast

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    I know on the Cherokee I had you can. Not too sure on this .
    I will have to look into that.
     
  6. Pearce

    Pearce Toyotaholic

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    I've heard of speedo correcting boxes that you custom order.
     
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  7. Pearce

    Pearce Toyotaholic

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  8. Perkolator

    Perkolator Toyotaholic

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    Maybe this will help. I once did some tinkering with an online RPM calculator to help figure out gearing for highway cruising speeds with different tire sizes and my w50 transmission. I realize some people use a 23" tire on these trucks when lowered, but you can guesstimate.

    I couldn't really find anything local, so I was looking at buying a used higher geared 8" 30-spline differential on eBay, but they're all still like $250+

    W50 trans gear ratios: 1st 3.28, 2nd 2.04, 3rd 1.394, 4th 1:000, 5th 0.853, Reverse 3.769

    4.10 gearing @3510 RPMs:
    26" tires - 78mph
    25" tires - 75mph
    24" tires - 72mph

    3.73 gearing @3510 RPMs:
    26" tires - 85mph
    25" tires - 82mph
    24" tires - 79mph

    3.58 gearing @3510 RPMs:
    26" tires - 89mph
    25" tires - 85mph
    24" tires - 82mph

    3.14 gearing @3510 RPMs:
    26" tires - 101mph
    25" tires - 97mph
    24" tires - 94mph
     
  9. Liquidhandwash

    Liquidhandwash Enthusiast

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    if you're not worried about the odometer been accurate, you can adjust the needle by holding the speedometer drum and removing the needle and refitting it in the correct position. I've done it on a couple of vehicles and it works just fine. let me know if you need for info.
     

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