SLeepY_BoY

hi all, just bought a 6spd jk, and top speed in 4th is 170kmph( i think thats around 105 mph), i was just wondering if anyone who has regeared to 4.88 knows what the top speed in 4th is,.....

SLeepY_BoY

anyone????

jeeperjkj

I guess it'd just depend on your tire size and gear ratio. There are calculators all over the 'net. Fill in the numbers and see.

jeeperjkj

For instance...

4th gear (1.25:1, I think)
32" tires
4.10:1 gear ratio
6000 rmp
1:1 tcase ratio (HI)

results in 111.5mph.

I think you'd be crazy to do that in a JK, though. Good luck.

SLeepY_BoY

dont get me wrong, im not planning on drag racing in a jeep , i just want to know how much the jeep would gear down.. and it seemed like 4th gear feels the the right one to compare stock to 4.88 ratio...

Okie4WD

Your probably better off looking at what RPM you want to run at then compare the gears.

Word of mouth is for 35" tires, 4.88 is necessary and 5.13's are even better.

With a stick, 4.88 would be just fine.

TEEJ

Well, it depends on what tires and stock gears you have...

For example, your 6 spd JK might have diffs with 3.21, 3.73 or 4.10 gearing...that will make a difference on your estimate of 105 mph in 4th, etc.

Now, dropping from 6th to 4th drops you about 32.8%...as you are going from the 6th speed's 0.84 ratio, to 4th gear's 1.25 ratio.

Going from 3.21 to 4.88 diffs drops your rpm by 34.2 %, very close to the 6th to 4th shift.

IE: Driving in 4th with 3.21 gears in the diffs, is like driving in 6th with 4.88's in the diffs....including what top speed you'd top out at.

If you have the 3.73's in your diffs, going to 4.88's drops your rpm by about 23.6%.

And so forth.

Hope that helps!

(Tell me the tire size and diff ratios, and I can tell you more specifically)

69thunderbird

check this site out - this is what your speedometer should read -

http://www.angelfire.com/fl/procrastination/rear.html

SLeepY_BoY

WOW... thx dude nice site helped me alot

jeeperjkj

Looks right to me... assuming no change in tire size.