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RV-related and other recreational activities => 4-wheeling => Topic started by: bunce on February 03, 2019, 12:04:53 PM

Title: lifting jeep
Post by: bunce on February 03, 2019, 12:04:53 PM
Going to put a 21/2 in lift on a 2010JK. Also getting new rims and 35in tires. Somewhere I heard that I may have to change the gearing in the rear because of the larger tire size is this true? I have a 6 speed transmission if that makes any difference?
Title: Re: lifting jeep
Post by: Old_Crow on February 04, 2019, 07:34:39 AM
Well, your speedometer is going to be off, and if my experience with an old 2.5l/5sp YJ is any indicator, 6th gear won't be of much use.  However, I'm sure there's plenty of people out there running 35's with stock gearing.

More important, if this Jeep is your toad, make sure the tow bar is sitting level when you're hooked up to the coach.  You might have to change the ball mount to a different one with less drop.
Title: Re: lifting jeep
Post by: dkreuzen on February 04, 2019, 09:20:01 AM
It depends on what gear ratio your JK has now. Here is a set of charts to help you decide.

https://prodigyperformance.com/blog/jeep-wrangler-gear-ratio-calculator/

Even if you start with a Rubicons 4:10 ratio you won't be using 6th gear much.
Title: Re: lifting jeep
Post by: packnrat on March 09, 2019, 07:41:34 PM
not sure of the room on a jk. but for my cj-7, i run 35in mud tires. a 4 inch lift, with 4.10 gearing. this runs about stock. i only use a 4 speed box with compound low, no overdrive and 65 mph no problem, easy on the motors rpms.
but if your towing 4 down you are better off getting tires that are made for pavement not mud tires like i run. my jeep is just street legal, it lives for crawling on rocks.
Title: Re: lifting jeep
Post by: zmotorsports on May 13, 2019, 10:11:18 AM
I know this is a few months old and not sure if the OP has done anything yet, but if you have a 2010 it will have the 3.8 liter engine and it is not exactly a ball of fire so going to 35" tires will feel like you're dragging a boat anchor around unless you regear.  It sounds like you have the manual 6-speed so that is a bit better but you will still want to regear for drivability as well as to get your mechanical leverage back and your economy to some extent.

If you had the 42RLE (4-speed automatic) it is even worse with the 3.8 liter and 35" tires.  When I was running the 3.8 liter engine in my 2011 I went from the OEM 4.10 gears to 5.38 gears and it was a night and day difference in drivability and I got some fuel economy back.

Now that I have around 425 horses and 8 cylinders I am sitting at 4.56 gears and it is a perfect combination with my now 37" tires.

Mike
Title: Re: lifting jeep
Post by: Roy M on May 13, 2019, 10:41:40 AM
Wow! I bet careless use of the right foot could lead to some serious breakage. ;D
Title: Re: lifting jeep
Post by: zmotorsports on May 13, 2019, 11:27:46 AM
Wow! I bet careless use of the right foot could lead to some serious breakage. ;D

If being careless, yes.  Good thing I don't drive carelessly and have good quality parts installed to handle the power.  I built the Jeep prior using necessary parts with the intentions of the LS swap so when I had the time and money to do the swap I didn't have to go back and rebuild the entire Jeep again.

Mike
Title: Re: lifting jeep
Post by: Lou Schneider on May 13, 2019, 12:05:45 PM
Somewhere I heard that I may have to change the gearing in the rear because of the larger tire size is this true?

If you change the gearing in the rear end you'll have to change it in the front axle also.   ;)