gear change ?

davem · 10-01-2008, 08:39 PM

i have an 08 rubicon with 35" tires. im doing a gear swap in the future and was wanting some ideas on what gears to go with. im thinking 4:88 . its a daily driver on the streets and sees some light mountain roads.

Hilldweller · 10-03-2008, 08:27 AM

AEV uses 4:88 in their Rubi build; I think it would suit your purposes unless you plan to tow a trailer. I'd go to 5:13 then.

skeejunkee · 10-06-2008, 12:59 PM

I have a friend who has an 08 rubi w/ 35 pro comp wheel and tires. He went w/ the 513 gears and said it was the best thing he did. The only problem was the break in on the gears took a while.

hig4s · 10-06-2008, 08:10 PM

Quote:

Originally Posted by davem

i have an 08 rubicon with 35" tires. im doing a gear swap in the future and was wanting some ideas on what gears to go with. im thinking 4:88 . its a daily driver on the streets and sees some light mountain roads.

Are you having some issues while in the lower gears? I would think with a 6 speed, you always have the option of not shifting to 6th and that would have the same effect as changing the gear ratio. I can't imagine needing lower gearing than the Rubi already has when you are in 4 low, unless you do some serious crawling.

Hilldweller · 10-07-2008, 11:44 AM

Quote:

Originally Posted by hig4s

Are you having some issues while in the lower gears? I would think with a 6 speed, you always have the option of not shifting to 6th and that would have the same effect as changing the gear ratio. I can't imagine needing lower gearing than the Rubi already has when you are in 4 low, unless you do some serious crawling.

Think tires. The 410 becomes almost a 321 by the time you get to 37". If he goes to 488, in essence he's back to about 410 with the 35's.
Not exact science, but you get the idea.
I'd stop at 488, btw. I think that 513 is overkill with 35's. Maybe if you had an auto, drove locally only, and pulled a trailer...

ballzout4 · 10-07-2008, 09:43 PM

im about to buy an X and it will be my first standard so i dont know much about this gearing stuff but im putting 35s under but no towing if i do the build on the internet i can upgrade the ratio from a 3.21 to a 3.73 for only $50 would that be enough?

Hilldweller · 10-08-2008, 08:00 AM

Quote:

Originally Posted by ballzout4

im about to buy an X and it will be my first standard so i dont know much about this gearing stuff but im putting 35s under but no towing if i do the build on the internet i can upgrade the ratio from a 3.21 to a 3.73 for only $50 would that be enough?

It would be enough for 33's but I think that you'd be wanting at least a 4:10 for 35's --- 4:88 would be better.
Unless you'll seldom see hills....

hig4s · 10-08-2008, 07:17 PM

Quote:

Originally Posted by Hilldweller

It would be enough for 33's but I think that you'd be wanting at least a 4:10 for 35's --- 4:88 would be better.
Unless you'll seldom see hills....

If 4:10 is good enough for the 35s on the X, why is it not good enough for the Rubi with 35s, which is what I said to start with?

Definitely get either the towing package which comes with 3:73 or the upgrade to 3:73. (all 09s 4doors come with 3:73) put whatever tires you want on first, see how it is to you, then decide on different gears or not.. Remember 35s will work on stock suspension, but will rub if you go off road, you really need a 2" lift and different wheels for 35s. Stock X wheels 7in wide are not wide enough for anything over 265/75-16 (32s), optional X wheels come with 255s and 7.5in wide wheels. They are OK up to 285/75-16 (33s). So to go to 35s you would need new wheels either way.

ballzout4 · 10-08-2008, 07:30 PM

well im doing a 5" lift and 17" helo wheels so ill be set there but how do i go about getting 4:10 or 4:88 and how much would it run me like i said its my first standard

davem · 10-08-2008, 08:17 PM

theres NO way 35's will fit with with no lift. my rubicon with a 3" bds lift the tires rubbed the front splash panel under the bumper . then i added daystar spacers for another inch and problem solved. 35"s no lift no way, not without major hacking.

Hilldweller · 10-09-2008, 08:17 AM

Quote:

Originally Posted by hig4s

If 4:10 is good enough for the 35s on the X, why is it not good enough for the Rubi with 35s, which is what I said to start with?

The 4:10 crawl is geared for 32's; you'll roll downhill faster & uphill slower if you go to 35's and don't regear.

Quote:

Originally Posted by Elwarpo

5 Speed 5th gear has a ratio of .78 in 5th
6 Speed 6th gear has a ratio of .84 in 6th
Auto has an overdrive gear ratio of .69 in overdrive

Most people agree the auto does not have enough torque on the highway when stock. Most people agree the 6 speed is better suited to 33s than 31s. No on complains about the 5 speed when stock. So I figure the .78 is good for a jeep. I have a 5 speed and 6 speed and used to own an auto so I have thousands of miles on all 3 transmissions when stock.

So if we change tires and gears we should try to keep it so we have the equivalent of a .78 tranny ratio.

So here are a few tire and gear options to keep it similar to the balance of torque and gas mileage of a stock 5 speed

33" tires
The 6 speed would require 4.10 gearing to behave the same as the 5 speed stock
The 5 speed would require 4.36, so choose 4.56 to be close to the 5 speed stock
The Auto would require 4.93 gears so choose 4.88 gears to be similar to the 5 speed stock.

35" tires
The 6 speed would require 4.30, so use 4.56
The 5 speed would require 4.63 so use either 4.56 or 4.88
The Auto would require 5.24 so use 5.13

37" tires
The 6 speed would require 4.55, so use 4.56
The 5 speed would require 4.89 so use 4.88
The Auto would require 5.53 so use 5.38

In cases where there are 2 choices it would be better to go to the higher number (lower gears) with the manual
Generally the Auto can get by with a slightly lower ratio, so you can use the gear ratio that is close but a bit lower.
If you rig has a significant surplus weight in armor and extremely heavy tires you may want to increase the gear number (lower ratio)

So far I liked the performance with my 5 speed stock (it had armor) and the 5 speed with 35s and 4.88 gears. I am unhappy with the stock auto, 5 speed with 33s and 4.10 gears or 4.88 gears and the stock 6 speed.

hig4s · 10-09-2008, 09:36 PM

Quote:

Originally Posted by davem

theres NO way 35's will fit with with no lift. my rubicon with a 3" bds lift the tires rubbed the front splash panel under the bumper . then i added daystar spacers for another inch and problem solved. 35"s no lift no way, not without major hacking.

You mean that stupid plastic air dam,, you still have that?? I've got stock tires and don't have that (well it is hanging in the garage. Either way, the backspacing is more important than the lift with 35s..

Daystar spacers???? Are you still using stock wheels?? Technically 35s are suppose to be on a rim minimum 8 inch wide.. Stock are 7.5 inch, but I do know a lot of guys that run 35s on stock rims with no problems.

And with no air dam and proper backspacing you can run on paved roads with 35s, (depending on how wide the 35s are, they are not all the same) I've seen guys do it. Just a little rubbing at full lock.. But if you want to wheel, you need a minimum of 2 1/5 lift and back spacing. Actually I have heard you can wheel with stock suspension and 35s (with proper backspacing) if you take your fenders off. Don't know of anyone that has tried that though.

bgjhnsn · 10-31-2008, 01:23 PM

I am running 35" and just put 4.88's in. Seems perfect. 75 mph at 2500 rpm.

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10-01-2008, 08:39 PM	#1
davem Jeeper Join Date: Sep 2008 Location: butler,pa Posts: 16	gear change ? i have an 08 rubicon with 35" tires. im doing a gear swap in the future and was wanting some ideas on what gears to go with. im thinking 4:88 . its a daily driver on the streets and sees some light mountain roads. __________________ 08 rubicon ,6 spd, mygig w/nav, 3" bds lift, 1" daystar spacers, bds steering stabilizer, 35" pro comps w/ pro comp wheels, k&n replacement filter, pro comp lightbar w/ 8" kc lights,

10-03-2008, 08:27 AM	#2
Hilldweller Jeeper Join Date: Apr 2008 Location: Canton, GA; aka Podunk Posts: 275	AEV uses 4:88 in their Rubi build; I think it would suit your purposes unless you plan to tow a trailer. I'd go to 5:13 then. __________________ Safety fast, Bill

10-06-2008, 12:59 PM	#3
skeejunkee Jeeper Join Date: Feb 2008 Location: Social Circle GA. Posts: 94	I have a friend who has an 08 rubi w/ 35 pro comp wheel and tires. He went w/ the 513 gears and said it was the best thing he did. The only problem was the break in on the gears took a while. __________________ Life is better Topless: Drive a JEEP!

10-08-2008, 08:17 PM	#10
davem Jeeper Join Date: Sep 2008 Location: butler,pa Posts: 16	theres NO way 35's will fit with with no lift. my rubicon with a 3" bds lift the tires rubbed the front splash panel under the bumper . then i added daystar spacers for another inch and problem solved. 35"s no lift no way, not without major hacking. __________________ 08 rubicon ,6 spd, mygig w/nav, 3" bds lift, 1" daystar spacers, bds steering stabilizer, 35" pro comps w/ pro comp wheels, k&n replacement filter, pro comp lightbar w/ 8" kc lights,

10-07-2008, 09:43 PM	#6
ballzout4 Newb Join Date: Oct 2008 Posts: 9	im about to buy an X and it will be my first standard so i dont know much about this gearing stuff but im putting 35s under but no towing if i do the build on the internet i can upgrade the ratio from a 3.21 to a 3.73 for only $50 would that be enough?

10-08-2008, 07:30 PM	#9
ballzout4 Newb Join Date: Oct 2008 Posts: 9	well im doing a 5" lift and 17" helo wheels so ill be set there but how do i go about getting 4:10 or 4:88 and how much would it run me like i said its my first standard

10-31-2008, 01:23 PM	#13
bgjhnsn Newb Join Date: Oct 2008 Posts: 7	I am running 35" and just put 4.88's in. Seems perfect. 75 mph at 2500 rpm.

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