4.10's?

Terdl76 · **Posted:** Wed Apr 22, 2009 6:29 pm

ive been running 265/75/16's for sometime now. i've read several times now that i should re-gear to 4.10's. why? what are the pro's and con's? will i damage anything if i don't?

KJ kyle · **Posted:** Wed Apr 22, 2009 6:31 pm

you dont have to regear, but if you do, you will get better gas milage, and gain some power back.

CRD Joe · **Posted:** Wed Apr 22, 2009 6:51 pm

Let's see, Gasser V6 manual 3.55, gasser V6 auto 3.73 Gasser 4 cyl 4.10

CRD Auto 3.73

So, if youre a gasser V6 manual you'll probably want to re-gear to 4.10.
If youre a gasser V6 auto maybe not.

If youre a gasser 4 cylinder youre there already.

If youre a CRD (auto only damnit) probably not.

tommudd · **Posted:** Wed Apr 22, 2009 7:05 pm

CRD Joe wrote:

Let's see, Gasser V6 manual 3.55, gasser V6 auto 3.73 Gasser 4 cyl 4.10

CRD Auto 3.73

So, if youre a gasser V6 manual you'll probably want to re-gear to 4.10.
If youre a gasser V6 auto maybe not.

If youre a gasser 4 cylinder youre there already.

If youre a CRD (auto only damnit) probably not.

confused as to why some not and some you should. Anytime you run a larger tire you need (or should) re gear to bring ( whatever engine you have) back into that sweet spot that it has when running stock gears and tires. No matter what you have say with stock 29 inch tires and 3.73s it runs down the road at 70 MPH at 2100 RPM, move to a larger tire say a 32 inch and it drops to maybe 1750 ( just pulling numbers for argument sake) now you are lugging that engine below where it runs the best, no matter if diesel , gas , or moonshine

tommudd · **Posted:** Wed Apr 22, 2009 7:08 pm

Terdl76 wrote:

ive been running 265/75/16's for sometime now. i've read several times now that i should re-gear to 4.10's. why? what are the pro's and con's? will i damage anything if i don't?

better mileage
less wear and tear on the engine and drivetrain
more power

if you don't then yes you are lugging the engine more, more slippage in the trans etc.

of course someone will argue that point but... it makes a huge difference when you regear

Quicksilversurf917 · **Posted:** Wed Apr 22, 2009 7:43 pm

Where is a cheep place to get gears? Im looking for them bc im going to be switching to 31's here soon.

jsc7002 · **Posted:** Wed Apr 22, 2009 8:23 pm

Quicksilversurf917 wrote:

Where is a cheep place to get gears? Im looking for them bc im going to be switching to 31's here soon.

there is a huge thread about them in the General Section, and in there it has all of the places to buy the gears and overhaul kits and prices, but National Drivetrain was the cheapest for the 8.25 gears ebay for the 8.25 rebuild and TrailQuest for the D30a gears and rebuild, your looking at $650 plus shipping and install which should run you another $500 and if your opnly going with 31" you probably wont need them that bad but they will help.

tjkj2002 · **Posted:** Wed Apr 22, 2009 8:27 pm

Yep it's needed to save your trans and/or clutch if you have one.Pete drove my KL the other day and I have 4.10's and 32" tires,his KJ has 3.73's and 30.5" tires and the 1st thing he said was he needs to get 4.10's,he was that impressed on how much the difference was and I'm about 1000lbs heavier then his KJ also.

CRD Joe · **Posted:** Wed Apr 22, 2009 8:47 pm

tommudd wrote:

CRD Joe wrote:

Let's see, Gasser V6 manual 3.55, gasser V6 auto 3.73 Gasser 4 cyl 4.10

CRD Auto 3.73

So, if youre a gasser V6 manual you'll probably want to re-gear to 4.10.
If youre a gasser V6 auto maybe not.

If youre a gasser 4 cylinder youre there already.

If youre a CRD (auto only damnit) probably not.

confused as to why some not and some you should. Anytime you run a larger tire you need (or should) re gear to bring ( whatever engine you have) back into that sweet spot that it has when running stock gears and tires. No matter what you have say with stock 29 inch tires and 3.73s it runs down the road at 70 MPH at 2100 RPM, move to a larger tire say a 32 inch and it drops to maybe 1750 ( just pulling numbers for argument sake) now you are lugging that engine below where it runs the best, no matter if diesel , gas , or moonshine

Because everything is a compromise. I've re-geared five trucks over the years. All with Randy's Ring and Pinion Service (Yukon) gears and ARB lockers.

Everything is a compromise. You have to factor everything into the equation. It makes a difference how big your tires are going to be above stock as to whether it makes since to drop the money to re-gear. It matters whether you have a manual or an auto. It matters what kind of engine you have (I.E. six cylinder vs. four cylinder or diesel vs. gasser)

You dont properly re gear a truck cheaply! Its going to cost over a thousand dollars for good gears, install kits and labor to do it. And if you havent ever done it you shouldnt start now on your daily driver!

For example Im going to buy a CRD KJ. The Limited came with 235/65-16's if I only increased the tire size by an inch or an inch and a half it might not make sense to re-gear because that engine has the torque to move those tires better than either the four banger or the V6.

My point is that you have to factor everything into it. Another example, Im going to have a diesel, you dont wan to re-gear and have that engine running to many RPM's on the freeway. Everything must be considered......

Dont re-gear without thinking about everything.

tjkj2002 · **Posted:** Wed Apr 22, 2009 8:54 pm

CRD Joe wrote:

tommudd wrote:

CRD Joe wrote:

Let's see, Gasser V6 manual 3.55, gasser V6 auto 3.73 Gasser 4 cyl 4.10

CRD Auto 3.73

So, if youre a gasser V6 manual you'll probably want to re-gear to 4.10.
If youre a gasser V6 auto maybe not.

If youre a gasser 4 cylinder youre there already.

If youre a CRD (auto only damnit) probably not.

confused as to why some not and some you should. Anytime you run a larger tire you need (or should) re gear to bring ( whatever engine you have) back into that sweet spot that it has when running stock gears and tires. No matter what you have say with stock 29 inch tires and 3.73s it runs down the road at 70 MPH at 2100 RPM, move to a larger tire say a 32 inch and it drops to maybe 1750 ( just pulling numbers for argument sake) now you are lugging that engine below where it runs the best, no matter if diesel , gas , or moonshine

Because everything is a compromise. I've re-geared five trucks over the years. All with Randy's Ring and Pinion Service (Yukon) gears and ARB lockers.

Everything is a compromise. You have to factor everything into the equation. It makes a difference how big your tires are going to be above stock as to whether it makes since to drop the money to re-gear. It matters whether you have a manual or an auto. It matters what kind of engine you have (I.E. six cylinder vs. four cylinder or diesel vs. gasser)

You dont properly re gear a truck cheaply! Its going to cost over a thousand dollars for good gears, install kits and labor to do it. And if you havent ever done it you shouldnt start now on your daily driver!

For example Im going to buy a CRD KJ. The Limited came with 235/65-16's if I only increased the tire size by an inch or an inch and a half it might not make sense to re-gear because that engine has the torque to move those tires better than either the four banger or the V6.

My point is that you have to factor everything into it. Another example, Im going to have a diesel, you dont wan to re-gear and have that engine running to many RPM's on the freeway. Everything must be considered......

Dont re-gear without thinking about everything.

es but you start adding armor and that weight will bog down that smoker,regearing will regain lost power.When I switched to 4.10's I also added about 1000lbs of weight and my rpm's at 75mph did not change one bit since the tire size and added weight bogged the engine down.Oh I was running 265/75's both with 3.73's and 4.10's,it make a big difference.

With the lack of low end of the 3.7 I'm going to 5.13's when I SFA and sitting on 35" tires.

Quicksilversurf917 · **Posted:** Wed Apr 22, 2009 9:02 pm

I want to get some 4.10's to resotre my power and I need better gas mileage like no other.. (average 15mpg) :evil:

tjkj2002 · **Posted:** Wed Apr 22, 2009 9:07 pm

Quicksilversurf917 wrote:

I want to get some 4.10's to resotre my power and I need better gas mileage like no other.. (average 15mpg) :evil:

I went from 6-8mpg's(winter-summer) city and 15-16mpg's on the highway to 10-13mpg's(winter-summer) city and almost 22mpg's on the highway when I switched to 4.10's.

tommudd · **Posted:** Wed Apr 22, 2009 9:08 pm

CRD Joe
I fully realize how much it cost after doing several also over the years and NEVER have I regretted spending the money that it costs, I used to run 38s/40s on everything and they were my daily drivers, so they got used everyday and to regain the power/ fuel mileage that I lost was well worth it in the long run.
Been doing this little 4WD game for over 30 years now, I know what works, what doesn't, whats worth it :wink:

CRD Joe · **Posted:** Wed Apr 22, 2009 9:18 pm

tommudd wrote:

CRD Joe
I fully realize how much it cost after doing several also over the years and NEVER have I regretted spending the money that it costs, I used to run 38s/40s on everything and they were my daily drivers, so they got used everyday and to regain the power/ fuel mileage that I lost was well worth it in the long run.
Been doing this little 4WD game for over 30 years now, I know what works, what doesn't, whats worth it :wink:

No disrespect meant there Tom. I was just trying to point some things out. I might end up re gearing to 4.10's myself when all gets said and done. I'll have to do all the calculations based the tires I end up with and that transmissions final drive.

Tom

KY Liberty · **Joined:** Sat Jul 09, 2005 1:46 pm **Posts:** 1195

You should go to 4.10's if your KJ feels sluggish off the line with the bigger tires.

Mine was the original 4.10 swap on a 3.7 KJ. I originally went to Yukon 4.10's in the rear and swapped in a 4 cylinder diff up front while running 245/70R16's that were about 29.5". I did it for the increased power off the line when I was running a 100 hp shot of N2O. It was ridiculous. I could keep up with a Lightning. Over 335 hp and 400 #ft torque in a KJ was very surprising.

I'm not running any juice since blowing up that motor, and have lifted it and gone to 245/75R16's that are about 30.5" No one who rides in my KJ can believe how much more powerful it is than a stocker. Of course, mine has a ton of modifications other than just the gears. You should have seen the look on the faces of the 2 other guys in my Jeep as I roasted the tires and whipped the rear end around pulling into KFC for lunch today. Priceless... Glad I was friends with 2 of the 3 cops that happened to be eating there since I didn't see their cars until I was in the lot. However, power can come at a cost. I only average 11.5 mpg in town and 15 mpg interstate. You should get better gas milage than me if you don't do all the mods I have and don't have a bad case of lead foot like me.

2006 KJ · **Posted:** Wed Apr 22, 2009 10:42 pm

i have a 6 speed with the 3.55's and i'm running 265/75/16 mudders and steel wheels with full armor, arb, winch...ect.. and i KNOW i can use the 4.10's... but cant afford them (darn college)... however i have a very low first gear which makes driving mine live-able. i need to use 5th for large hills sometimes but that's no big deal. plus i can still burn tire in 1st gear (in fact i laid two black strips on my driveway today) :twisted:

.. but stock i could get them to chirp the whole way though 3rd... it ran like the wind and it would be nice to have that back with 4.10's. right now.. in snow,town,highway, whatever i get 16mpg...

the thing i worried about with 4.10's is what my rpm's would be going 60 or 70 since a lot of my driving is at those speeds.. right now in 6th gear going 60 it's right at 1950rpms... i'm afriad with 4.10's it would be at something crazy like 2750... and over 3000 at 70mph

Terdl76 · **Posted:** Wed Apr 22, 2009 10:47 pm

thanks for all the input. most likely i'll go to 4.10's. a little rich for my blood, anyone in the d.c., baltimore area know how to install? likes to work for booze? btw, try 12.1 mpg. thats what the overhead says anyway.

MP Jeeper · **Posted:** Wed Apr 22, 2009 11:21 pm

KY Liberty wrote:

Mine was the original 4.10 swap on a 3.7 KJ. I originally went to Yukon 4.10's in the rear and swapped in a 4 cylinder diff up front while running 245/70R16's that were about 29.5".

So one can simply swap the front dif on a 3.7L with the front dif of a 4 banger straight up when switching to 4.10's? Is it simple as a straight swap or are there other modifications involved (other than 4.10's to match in the 8.25)?

Forgive if this seems a dumb question but we all know this is "learn as you go" and, well . . . i'm learning. :wink:

tommudd · **Posted:** Wed Apr 22, 2009 11:55 pm

MP Jeeper wrote:

KY Liberty wrote:

Mine was the original 4.10 swap on a 3.7 KJ. I originally went to Yukon 4.10's in the rear and swapped in a 4 cylinder diff up front while running 245/70R16's that were about 29.5".

So one can simply swap the front dif on a 3.7L with the front dif of a 4 banger straight up when switching to 4.10's? Is it simple as a straight swap or are there other modifications involved (other than 4.10's to match in the 8.25)?

Forgive if this seems a dumb question but we all know this is "learn as you go" and, well . . . i'm learning. :wink:

IF and thats a big If you can find one out there ( 4cyl.4 wheel drive) sure go ahead or some just ordered a new one from the dealer, switch it right out same everything but 4.10s :wink:

0311_DoC · **Posted:** Thu Apr 23, 2009 12:45 am

I got my 4.10's done and have put about 800 miles on them since install. I also added a power module. I honestly don't notice much difference other then I maybe gained 1MPG on avg...

So im beginning to wonder if I got a bad deal or not...

4.10's?

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