Limited Slip and 4:10 gears

jwheeles · **Joined:** Sun Jun 11, 2006 6:59 am **Posts:** 10

I am about to put a limited slip unit in my KJ and at the same time I am considering changing the rear gears. I had decided to put the PowerTrax unit in but have read several negative comments on the unit. I am now considering the Detroit TruTrac unit.

What kind of experience have you guys that have used the TruTrac had with it.

What kind of difference will the 4:10 gears in the rear have on acceleration and mileage. I am currently getting 13-14 MPG in around town driving and 18-19 MPG on the highway. With the 245-75-16 tires it feels like it is missing a lot on the bottom end. I know this goes against general wisdom but it seems I have to work the engine harder to get it to take off at time. Is it possible that the difference between the 3:73 and 4:10 gears might not make that much difference. I did the math using a formula I found somewhere on the internet and come up with about 200 RPM more at 70 MPH with the 4:10 and 245-75-16 tires compared to the 3:73 and 225-75-16 stock tires.

Anybody got any experience, thoughts, or other wisdom that might be helpful?

Also, has anybody got any part numbers for the TruTrac and 4:10 gears?

Thanks for any help

James

tommudd · **Posted:** Tue Feb 26, 2008 9:53 am

of course it takes more to take off now due to a taller tire, heavier etc, going to 4.10s will bring back some of the low end torque and mileage

tjkoen01 · **Posted:** Tue Feb 26, 2008 11:49 am

I'm in the same boat, same size tires and same gas mileage. I've been toying with the idea of going with 4.10's as well. Thinking about the LS as well. Let me know what you end up doing.

Neatus · **Posted:** Thu Feb 28, 2008 3:53 pm

I added the 4:10s and it helped a lot with towing and a little with gas mileage after the lift and bigger tires.

jwheeles · **Joined:** Sun Jun 11, 2006 6:59 am **Posts:** 10

Thanks for the info guys.

jwheeles · **Joined:** Sun Jun 11, 2006 6:59 am **Posts:** 10

I have sent emails to several companies about part numbers (particularly the gears) and haven't got a reply from one of them.

jwheeles · **Joined:** Sun Jun 11, 2006 6:59 am **Posts:** 10

Hey Neatus,

What kind of trailer do you pull with your Liberty? I have a 5 x 8 enclosed trailer that I pull on the interstate on occasion between Huntsville, AL. and St. Louis, MO. It does fine on the level parts but it struggles on hills. I think the gears might help with that. I really have to turn the engine to keep 65 MPH on the hills. Gas mileage goes to you know where too.

Just curious about how much difference it made.

Thanks.

_UnLiMiTeD_ · **Posted:** Thu Feb 28, 2008 7:01 pm

dont you have to replace the gears in the front and rear? because if you were to use 4hi and it locks them, wouldnt it not work being 2 different gear ratios?

tjkj2002 · **Posted:** Thu Feb 28, 2008 8:00 pm

_UnLiMiTeD_ wrote:

dont you have to replace the gears in the front and rear? because if you were to use 4hi and it locks them, wouldnt it not work being 2 different gear ratios?

He has a 2wd KJ.

BeepBeepJeepJeep · **Posted:** Thu Feb 28, 2008 9:08 pm

Save your money and get an air locker. (assuming you wheel your Libby)

_UnLiMiTeD_ · **Posted:** Fri Feb 29, 2008 1:54 am

tjkj2002 wrote:

_UnLiMiTeD_ wrote:

dont you have to replace the gears in the front and rear? because if you were to use 4hi and it locks them, wouldnt it not work being 2 different gear ratios?

He has a 2wd KJ.

oh...didnt see that, figured when he said lift and tires, i assumed 4x4 lol

Neatus · **Posted:** Fri Feb 29, 2008 2:21 am

jwheeles wrote:

Hey Neatus,

What kind of trailer do you pull with your Liberty? I have a 5 x 8 enclosed trailer that I pull on the interstate on occasion between Huntsville, AL. and St. Louis, MO. It does fine on the level parts but it struggles on hills. I think the gears might help with that. I really have to turn the engine to keep 65 MPH on the hills. Gas mileage goes to you know where too.

Just curious about how much difference it made.

Thanks.

I pulled my car from NY to AZ and it did great. For work I just pull a small construction trailer pretty much daily and my motorcycles on the weekend. I pull the trailers to northern Arizona from Phoenix and it does fine through the mountains. My gas mileage always sucks when I have even an empty trailer hooked up.

jwheeles · **Joined:** Sun Jun 11, 2006 6:59 am **Posts:** 10

Hey _UnLiMiTeD_

Yeah, It's a poser. I do some real easy stuff in it. I really need the locker for snow. I moved to a place that seems to snow all the time. I want the 4:10 gears because I just don't like the mileage and the way it takes off with the bigger tires. It also struggles pulling the trailer on hills. I can't believe how much difference the tires made in the gearing on the Libby.

jwheeles · **Joined:** Sun Jun 11, 2006 6:59 am **Posts:** 10

I ordered parts today. I ordered the Detroit TruTrac locker and the 4:10 gears from Richmond Gear. Now I'm looking forward to them getting here and finding somebody to install them.

Actually, I ordered the locker from 4 Wheel Parts Online and the gears from Summit Racing. After I looked at what I wrote it looked funny!

Jeepjeepster · **Posted:** Thu Mar 06, 2008 7:46 pm

Let us know how that limited slip does! Ive been toying with the idea of getting one.

And you cant expect to go 65mph on hills while towing jwheeles. I tow a small boat and it gets down to 45mph on some hills. I keep it in 3rd though, dont like those hard downshifts into 2nd while towing.

jwheeles · **Joined:** Sun Jun 11, 2006 6:59 am **Posts:** 10

I have it at Bigfoot 4 x 4 in St. Louis. It's the same people that do the bigfoot trucks. Hopefully I'll have it back in a couple of days and I'll post what I think about it all.

jwheeles · **Joined:** Sun Jun 11, 2006 6:59 am **Posts:** 10

We will see how it does long term but on first drive it definitely has more bottom end in it with the 4:10 gears. There is also more of a whine coming from the rear with the TruTrac and the gears. Nothing that seems abnormal or real loud. Just more like a truck.

I'll have to see about MPG's and get in something slick or loose to tell about the traction. On the highway I couldn't tell any difference.

Glad to have it back.....

Limited Slip and 4:10 gears

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