Effects of gearing

tjkj2002 · **Posted:** Tue Feb 10, 2009 7:06 pm

Well there was a heated topic over on the CO4x4 board about gearing and increasing torque #'s on a chassis dyno.Here are the dyno graphs,vehicle is a '08 JK Rubicon Unlimited with the 1st run with 37" tires and stock 4.10 gearing,the 2nd run is with 5.13 gears and no other mods.

Here is a link to the thread--http://www.colorado4x4.org/vbb/showthread.php?t=141443

Let the war begin but the dyno didn't lie,more useable torque to the ground when geared correctly.

KJ kyle · **Posted:** Tue Feb 10, 2009 7:25 pm

dont think anyone can argue with that. nothing but benefits when you are properlly geared.

tommudd · **Posted:** Tue Feb 10, 2009 7:27 pm

huge notable difference for sure, people don't realize how much difference in driveability it can make.
That shows it right there though!

Thanks for posting Troy!

TAHOE · **Posted:** Tue Feb 10, 2009 7:34 pm

Looking at the graphs, it shows havingh the right gearing also allows engine to get the most power int he right rpm range. After I lifted my Astro w/3.42's and added31" tires, it was a dog. I changed over to 4.10's and it woke up immensely and got better gas mileage.

dieselenthusiast · **Posted:** Tue Feb 10, 2009 7:36 pm

Too bad we don't have the same dyno results for the Kj 3.73 vs 4:10

jsc7002 · **Posted:** Tue Feb 10, 2009 7:38 pm

dieselenthusiast wrote:

Too bad we don't have the same dyno results for the Kj 3.73 vs 4:10

exactly what I was thinking! I would love to see the difference there. Ill do it if someone wants to pay for my dyno :wink:

JJsTJ · **Posted:** Tue Feb 10, 2009 7:46 pm

Guess I would have to go check out the CO4x4 thread but I don't understand What the argument would be about.

Did someone think that it Wouldn't make a difference??

tjkj2002 · **Posted:** Tue Feb 10, 2009 7:53 pm

JJsKJ wrote:

Guess I would have to go check out the CO4x4 thread but I don't understand What the argument would be about.

Did someone think that it Wouldn't make a difference??

Yep,they said it was impossible,lots of mumbo-jumbo tech talk that was proven wrong.

dieselenthusiast · **Posted:** Tue Feb 10, 2009 8:21 pm

tjkj2002 wrote:

JJsKJ wrote:

Guess I would have to go check out the CO4x4 thread but I don't understand What the argument would be about.

Did someone think that it Wouldn't make a difference??

Yep,they said it was impossible,lots of mumbo-jumbo tech talk that was proven wrong.

And let me guess…………now they’re probably arguing that the dyno results can't be compared to real world driving. :roll:

LibertyFever · **Posted:** Tue Feb 10, 2009 8:38 pm

This dicussion has me thinking. Please correct me if I put my foot in my mouth but stock Libby tires are about 29" and the biggest tire is a maximum of 32". When you are driving with the larger tires do you really notice the loss of power? I imagine it would through off your speedo and maybe the transmission shift points.

I have a 5 spd YJ that also came with 29" stock tires and when I upgraded to 33" tires I really noticed the loss in power. I could barely get up hills and seldom used 5th gear. Now that I've regeared (went from 4.10 to 4.88) I really notice the difference. It drives like I had the stock tires on it again and crawls like a beetle.

Here's a useful link for calculating your crawl ratio
http://www.4lo.com/calc/geartable.htm

jsc7002 · **Posted:** Tue Feb 10, 2009 8:40 pm

LibertyFever wrote:

This dicussion has me thinking. Please correct me if I put my foot in my mouth but stock Libby tires are about 29" and the biggest tire is a maximum of 32". When you are driving with the larger tires do you really notice the loss of power? I imagine it would through off your speedo and maybe the transmission shift points.

I have a 5 spd YJ that also came with 29" stock tires and when I upgraded to 33" tires I really noticed the loss in power. I could barely get up hills and seldom used 5th gear. Now that I've regeared (went from 4.10 to 4.88) I really notice the difference. It drives like I had the stock tires on it again and crawls like a beetle.

Here's a useful link for calculating your crawl ratio
http://www.4lo.com/calc/geartable.htm

it makes a difference, I have noticed a power loss and definitely a MPG loss but the KJ is really heavy to begin with and I have added a lot of extra weight.

MtnLuvr · **Posted:** Tue Feb 10, 2009 10:34 pm

Nice post tjkj2002. Good "visual proof".

jsc7002 wrote:

dieselenthusiast wrote:

Too bad we don't have the same dyno results for the Kj 3.73 vs 4:10

exactly what I was thinking! I would love to see the difference there. Ill do it if someone wants to pay for my dyno :wink:

Yeah, I'd be interested in seeing directl KJ/KK results from 3.73 to 4.10 too .....

2006 KJ · **Posted:** Tue Feb 10, 2009 10:51 pm

jsc7002 wrote:

LibertyFever wrote:

This dicussion has me thinking. Please correct me if I put my foot in my mouth but stock Libby tires are about 29" and the biggest tire is a maximum of 32". When you are driving with the larger tires do you really notice the loss of power? I imagine it would through off your speedo and maybe the transmission shift points.

I have a 5 spd YJ that also came with 29" stock tires and when I upgraded to 33" tires I really noticed the loss in power. I could barely get up hills and seldom used 5th gear. Now that I've regeared (went from 4.10 to 4.88) I really notice the difference. It drives like I had the stock tires on it again and crawls like a beetle.

Here's a useful link for calculating your crawl ratio
http://www.4lo.com/calc/geartable.htm

it makes a difference, I have noticed a power loss and definitely a MPG loss but the KJ is really heavy to begin with and I have added a lot of extra weight.

took it's toll on mine too.. i'm running 32's and i have 3.55 gears :shock:

i can still live with mine though.. it was just the difference of starting in 1st all the time instead of 2nd all the time... and sometimes (rarely but still) i have to use 5th gear instead of 6th to maintain 60mph going up real big hills.

i bet with 4.10's i could smoke the back tires though 3 gears :twisted:

dieselenthusiast · **Posted:** Tue Feb 10, 2009 11:12 pm

I'll take 4:10's with a 30.0-30.5 inch tire mounted on a 15" rim, then I'll have plenty of power for towing my camper and I'm still left with enough sidewall rubber to air down on the trail.

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

I wish I had done before and after dyno runs when I went from 3.73 to 4.10 gears. I'm really not very fond of the way these dyno runs were done. There is way too much math and corrections done to them. They are also calculating engine hp and torque. Also, does this JK have over 1000 lbs of added goodies? I would love to have seen them do non-corrected rear wheel numbers instead, or even SAE corrected instead of these numbers.

Dyno's don't lie, but the people running them can make them say whatever they want. While I don't doubt that there was an increase in torque at the wheels, these graphs don't do much for me.

MNKK · **Posted:** Wed Feb 11, 2009 3:38 am

jsc7002 wrote:

I have added a lot of extra weight.

Where???

KJ Willy · **Posted:** Wed Feb 11, 2009 6:31 pm

If someone wants to pay for Dyno Runs I will volunteer to sow the difference in 3.73 and 4.10 gears. I am just waiting on my rear locker to show up.

jsc7002 · **Posted:** Wed Feb 11, 2009 6:41 pm

KJ Willy wrote:

If someone wants to pay for Dyno Runs I will volunteer to sow the difference in 3.73 and 4.10 gears. I am just waiting on my rear locker to show up.

how much is it going to cost you for the re-gear?

KJ Willy · **Posted:** Wed Feb 11, 2009 7:24 pm

Install for all everything is looking at $1000 to $1500, still calling around to see what I can find.

Effects of gearing

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