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Gear ratio dilemma

Old 03-09-2019, 04:44 AM
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Gear ratio dilemma

I have been toying around with the Idea of regearing my 87 4runner 5spd 22re so I started looking into what gears would be best from what I can tell I want either 4.56 or 4.88. I never plan on running anything bigger than 33s. I started playing around with the gear ratio calculator on Grim Jeeper gear ratio calculator. And noticed that according to my RPM range, 3100-3200 at 70mph, I already have 4.88.... Everything thing about my truck says I should have 4.10s. Ive even jacked up one tire and spun it while watching the driveshaft with tape and in my best estimation it spun just over 4 times which would makes sense for 4.10s but like I said the RPMs are telling a different story. I dont wanna waste time going to a junkyard and pulling diffs out of a auto 2nd gen and swapping mine for no results. I attached some pictures including a photo from a stamping on the actual rear differential. I used tire size as 30 because right now I have worn 31x10.50R15 so the sctual size is probably close to 30. Any input or help is appreciated.





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Old 03-09-2019, 07:00 AM
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Your truck has 4.10's
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Old 03-09-2019, 01:35 PM
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Old 03-10-2019, 02:29 PM
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It is easier to note the ratio if you go around twice.

8-9-10 is a lot simpler to notice than is that .1 .5 or .8...

You can not trust the build tag, it could have been altered anywhere between the truck it left the factory on and now.

You can not trust the speedometer, for one they are allowed upto 5% error and more importantly tire size is almost never accurately displayed by manufacturers. To get an accurate tire size you have to measure it's rolling distance and math it out.
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Old 03-10-2019, 03:52 PM
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watching your driveshaft spin is subjective IMO.

like CO_94_PU said who knows who has done what to the truck over 30+ years

to me the only sure fire way to confirm the ratio is to pull the 3rd, count the ring gear teeth and divide by the pinion teeth

borrow a set of 33's and set how it does
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Old 03-10-2019, 06:13 PM
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Worthwhile to note seldomly tires are the size they are labeled, I.e. my 35x12.5x15 KM2s were actually 34.5 on an 8 wide rim. They would be even shorter if I had wider rims. Believe BFG states they used 9 wide rims on specs sheet. Add in wear from use and tire actual tire and diameter of tire can be significantly less than what you believe tire size to be.
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Old 03-11-2019, 04:37 AM
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Your speedo is not GPS corrected.
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Old 03-11-2019, 04:48 AM
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someone correct me if im wrong but im pretty sure Toyota paint marked the pinion for different gear codes, (pink, white, something something darkside) im sure you can find the thread on here somewhere. I aslo know that they wear off a lot so this may not help. I will also tell you that 4.88s with a set of 33s is a good life.
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Old 03-11-2019, 03:45 PM
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Originally Posted by ev13wt View Post
Your speedo is not GPS corrected.
where was that mentioned??
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