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Discussion Starter · #1 ·
I have a 98 sahara 4.0 auto trans on stock tires 225 x 75 x 15, it runs about 3000 rpm @ 60 mph that comes out to 4.10 gears. Does that sound rite did wranglers come with that low of gear from the factory?

I'm thanking of going with a 2 inch spacer lift and 32 x 11.50 tires on 10" wide wheels, Will there be any problems with this combo?

Oh yea 98% on road and the other 2% on loose sand.

Thanks
 

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if you air down your tires go with an 8" wide rim.....

a 10" wide rim with that tire and low pressure and you might have some problems losing yur bead

im pretty sure the 4.10 gears were only used in the 4 cylinder jeeps (?)
 

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No, that doesnt sound right to me. Remember the 98s didnt have an overdrive. If memory serves me...back then they had 3.08s with the auto and 4.0....maybe an option for 3.23s or 3.55s.
 
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Discussion Starter · #5 ·
Re: Lift, Tire & RPM ?

Yea 4.10 sure sounds low. But at 70 mph the tach is showing like 3400 rpm. How could I find out what I have?
I can tell both axle covers have been off at some point, Mabe a gear change but with the stock tires what would be the point.

Thanks Chris
 

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put blocks behind front wheels

put t-case in neutral

jack up one tire in the rear, leave one on the ground

turn the drive shaft, count how many times you have to turn the drive shaft to get the rear wheel to turn once, use chalk or something to mark the tire to keep track of where in the rotation it is.....

you should be able to estimate pretty closely....and then compare to known gear sets to get exactly what you have

pretty sure thats how its done at least, Lol /ubbthreads/images/graemlins/laugh.gif
 

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greg, because of the differential action...i dont think that would give an accurate reading. Try lifting both wheels off the ground.

Then again, maybe im wrong...im a pilot, not an engineer!;)
 

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Re: Lift, Tire & RPM ?

im an engineer, but not a good one! LOL

i think yur right.....i forgot about the change that would occur due to spider gears

i stand corrected /ubbthreads/images/graemlins/laugh.gif
 
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Discussion Starter · #9 ·
Re: Lift, Tire & RPM ?

Ok I tried both ways, with one tire on the ground its almost 2 full turns of the drive shaft to one of the tire.
With both tires tires off the ground its hard as hell to get both to turn at the same rate.
So when the wife gets home Ill see if she can help. Bet she will love that getting her hands all dirty. LOL
 

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With one tire on the ground and one in the air, turn the one in the air twice. The spider gears have a 2:1 ratio. Then just count the turns of the driveshaft.
 

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The subject comes up quite often. Search works pretty well now.

Here are some old threads found by searching for "gear ratio":

Gear Ratio

Gear/RPM Calculator

Gearing suggestions needed

What gear ratio do I have?

Don't forget there are lots of links to other threads in those threads.

If you read all of that you will find that I suggest you simply drain the axles and count the gears. Fresh GL5 is always a good idea and it doesn't take much time and effort.

/ubbthreads/images/graemlins/40BEER.gif
Dale
 

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There is also a good chance that a previous owner has swapped out the stock axles for ones from a 4 cylinder.
 
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