How do I know if I have 4.11s? (1 Viewer)

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Dec 26, 2008
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Ottumwa, IA
I have an 86 FJ60 and the previous owner said it had gear work done to it but I didn't get any more information than that. It has a H55F and 33s, it doesnt seem too doggish but I am looking for a little more in low. It runs 55mph on the spedometer at 2k rpm.
 

2mbb

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the speedometer won't know if you have new gears or not because the "speed" is measured at the transfer case. If you have a GPS you can measure your true speed at RPM, then do the math to figure out what your gears are. Or you can put the transmission in neutral, lift the rear tires off the ground and turn one wheel one full rotation. if the drive shave goes through less than four full rotations, then you have 3.73, if it goes through a little over four, you probably have 4.11's.

Or you can drain the oil and pull the rear inspection cover and find the numbers stamped on the gears or just count the gears.
 

SHERMAN FJ62

Charlestons' King of Cruisers
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If it is a 60 it is probably 3.73. There is some way you can add up the amount of teeth on the gearing to figure out the ratio.
 
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Try this gear calculator, enter 4.11's and if your rpms match that is what you have, if not more than likely 3.70's. Which is stock for 60's in the US. More than likely it has stock 3.70's as I think he would remember the bill for changing them out to 4.11's

Gear Ratio Calculator

Tony

If you want to do the math, divide the number of teeth on the ring gear by the number of teeth on the pinion gear, got to pull the cover to do this.
 

Butt Ugly Chuck

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In a 60 DOWN BY THE RIVER!!
 
 
Or you can put the transmission in neutral, lift the rear tires off the ground and turn one wheel one full rotation. if the drive shave goes through less than four full rotations, then you have 3.73, if it goes through a little over four, you probably have 4.11's.
If you're not locked, lift one tire and turn two full revolutions. The rest same as above.
Butt
 
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Try this gear calculator, enter 4.11's and if your rpms match that is what you have, if not more than likely 3.70's. Which is stock for 60's in the US. More than likely it has stock 3.70's as I think he would remember the bill for changing them out to 4.11's

Gear Ratio Calculator

Tony

If you want to do the math, divide the number of teeth on the ring gear by the number of teeth on the pinion gear, got to pull the cover to do this.
This is true, BUT, you need speed timed from mile markers, or GPS. Your indicated speed does not matter for this calculator. That's what I was trying to say in my last post.

Or, Butt's method is certainly easier than pulling the rear cover off the diff (unless you were planning on changing fluid anyway).
 
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The Northern of Va.
Do a GPS speed at a nice even number, 50, 60, etc... and note your revs then use the grimmjeeper site. Thats how I figured out I have 4.11s
 

ntsqd

technerd
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Easiest way to determine axle ratio that I've seen is to block the front tires so it can't roll, duct tape a piece of string to the drive-shaft, jack up the rear axle until both rears are off the ground, spin a rear tire exactly one revolution, count the number of times and the string is wrapped around the drive-shaft at the edge of the duct tape, add any partial drive-shaft revolution.
 

BlueCruiser84

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With 33's, 3.73s, and the stock tranny I was spinning 2500 rpms at "55" mph on the speedometer. I bet you have 3.73s.

**Edit - I was also keeping up with 65ph traffic on the highway.
 
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