Re-gearing my 80

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NW-sickboy

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I have recently purchased an 97 FZJ80 and am beginning the building process. It has factory locking diffs ( :D)and i am getting ready to lift and put 35's on. My concern is loss of gearing with going to the 35's. can you regear to say 4.56's or 4.88's and keep your factory lockers? I will obviously drive it and have to find out the power loss but i think it will be noticable in low range.thanks in advance for any input.
 
landtank

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4.56s with 35s will return you to stock...but the hell with that! Go with 4.88s ! You can still cruise at 85 easily and won't pine for that SC so much.
 
Riley

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So am I take it that a higher gear ratio number provides you with lower gearing in that you have more rpm at lower speeds?
 
NW-sickboy

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thanks for the input. I understand all the pro's of gearing down I just wanted to make sure it wouldnt affect my factory lockers. thanks. i plan on do 4.88's now and for sure I willl be able to put off going s/c. any input from anyone that has done this?
 
landtank

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I have this setup, factory lockers and 4.88s. Got the gears and bearing kits at Randy's ring and pinion on the web. You can get both front and rear gear sets with bearing sets for about the price of 1 factory gear set. Quite a bit of savings but if your a purist, factory sets are available. I chose to let the experts install them as well as doing the front axle since it was torn down at that time.
 
Rogue

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How would 4.88s do with 33" tires? I am just curious as I have a serious lack of fundage right now. I want to eventually run 35s and lower the bumpstops, but my MT/Rs have gone ~10k without losing much tread at all (currently @ 16\32), so I don't plan on switching anytime soon.

What would changing the gears do to the truck?
What would be my new ~top speed?

Am I an idiot? (Don't anwer this one Junk...)
:D
 
NW-sickboy

NW-sickboy

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re-gearing will restore power lost from going to a larger tire size. I understand the fundementals of gearing and with 33's and 4.88's you would be pretty low. I am guessing you could still go 80 with no issues. I really think gearing down is one of the best mods one can do to a rig, furhtermore I think if you are going large (35+) gearing down is a must so you dont lose the bottom end becuase that is where you will notice it the most. If i were you i would go 35's then gear down. just my 2 cents though.
 
Curran

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Rogue,
I'm in the same boat as you. I want to swap up for 315s but I currently ride on a set of 285 MTR's with 80% of the tread left. I talked to the guys at Randy's Ring and Pinion and their reccomendation was to go for the 4.88. Give them a call. There customer service is impressive.
CJ
 
T Y L E R

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In the interm , you could trade in the old rubber to 315's and purchase a Truspeed recallibrator . Not a completely satisfying solution , but it makes the 315s tolerable until the gear change .

Tyler
 
landtank

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Lets see if I can get this right...

4.10 and a 31.5" tire stock

4.88 and a 35" tire 35/31.5=11% change in tire
4.88/4.10=19% change in gearing
Or a combined change of 8% in increased RPMs

4.88 and a 33" tire 33/31.5=4.7% change in tire
4.88/4.10=19% change in gearing
Or a combined change of 14.3% in increased RPMs

So take your truck out and check the rpms at what ever speed then multiply that rpm by the appropriate percentage increase to see where you will be at. As Tyler pointed out you'll need something like the truespeed calibrator to correct shift points in the tranny with these setups.
 

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