regearing next monday

libertank · **Joined:** Sun Apr 25, 2010 5:20 pm **Posts:** 131

I've got a 2003 kj sport. Just got my last box from justdifferentals with my 4.10s front and rear with both master install kits going in next week. I've read pretty much every post on gears in lost kj and am alittle unsure. So my question is as of now I have 31in duratracs but plan on moving up to 32in bfgkm2s will the 4.10s be more fit for 31s or the km2s? Alot of people say regear after 32s but then I read that 31s and 4.10s are perfect. Thoughts suggestions? Anything is welcome. Any tips on when I should change diff fluid or the break in period should be?

ar-wg · **Posted:** Wed Oct 31, 2012 5:01 pm

I just regeared to 4.10s and am running DuraTrac 31s. This seems to be a really good combo. Not sure about the 32s.

Make sure you take it to a reputable shop that knows what they are doing. I learned this the hard way and had to have mine done twice by two different shops.

The second shop told me to run it 15-20 miles at a time and let it cool in between for the first 100 miles (all under 60 MPH). After 500-1000 miles is when you want to change the fluid.

tommudd · **Posted:** Wed Oct 31, 2012 5:20 pm

Personally.........
I'd like to have lower than 4.10s with my 32s, so 31s and those I think would be great
I'm actually thinking of dropping down a size for the next set of tires.
So if I was you I'd stay at 31s and enjoy the power :wink:

as far as break in yes run for a short while, let em cool, some more and cool, no hard take offs, 4 wheeling until broke in real good
Use regular Dino fluids also

libertank · **Joined:** Sun Apr 25, 2010 5:20 pm **Posts:** 131

Ar-wg. How did you know your gears were not done right? Any hard vibrations noise? And tommudd you've got the 32in duratracs. Are they true to size I believe the bfg km2s are about a half inch taller then listed compaired to the duratracs and heavier. Dont quote me on that though. Looks like I might just stick to a 31 bfg for the next set.

ar-wg · **Posted:** Wed Oct 31, 2012 6:14 pm

They were howling/whining like a mother f-er. Really really bad. The second shop took it apart and said the front ring and pinion were barely touching and I was lucky that that teeth didn't shear off and cause damage to the aluminum diff.

The rear set was better, but still wasn't set-up correctly. So they did those too.

I think you would be happier with the 31s.

Ryn7 · **Posted:** Thu Nov 01, 2012 8:41 am

31" tall tires and 4:10 gears are an excellent setup.
I'd want at least 4:56's if I went to 32's. But seeing that's not gonna happen, I'll
stick to 31" tires.

libertank · **Joined:** Sun Apr 25, 2010 5:20 pm **Posts:** 131

Looks like my next tire will be the bfgkm2s 31x10.5. Im not sure ill be ready to give up the power Im just now getting back after I lifted it over two years ago "long awaited by the way" I saw online that the 31in duratracs measure out to be 30.5s and if I did go up to the 32s or even 33s that the bfg makes that's just to much of a diffrence in size. Even though I have removed liners, bedlined wheelwells cut fenderflares extended bumpstops and limiting straps on the front, And just recently replaced cv shafts with jba cut ones. Ied rather not grenade my front diff with brand new gears in it despite my strange infatuation with 33s. But back on track. the rear gears went in today with no major problems. front wont be worked on until Monday so the anticipation will be killer until then. Thanks for the imput guys It answered some last minute questions I've had.

tommudd · **Posted:** Fri Nov 02, 2012 3:45 pm

Depends a lot on where and how you use the KJ as well.
If I was only driving in Northwest Ohio here where its flat as a pancake ( and I hate it

) , then mine has enough power.
But when I go down home where its hills and crooked roads I wish I had some more low end power, like 4.56s :twisted:

Also weight of tires/wheels makes a huge difference as well.

libertank · **Joined:** Sun Apr 25, 2010 5:20 pm **Posts:** 131

I live in the shenandoah valley here in virgina. 30 minutes in any direction are mountains plus my jeep sees 80% intown light to light driving. Granted alot of great places to go wheeling but the jeep hates the ride there or anywhere outside of my city So the 4.10s were needed in my opinion. But 4.56s would make her a nail biter. But ohhwell. Ill be just as happy with the 4.10s.

tommudd · **Posted:** Sat Nov 03, 2012 3:13 pm

You'll notice a big difference once you get them broke in.
Trans won't be trying to shift all of the time or won't have to run with the OD off :wink:

regearing next monday

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