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Topic Review (Newest First)
06-26-2013 08:20 AM
99GoldenSahara Has Goodyear beefed up the Duratrac sidewall recently? Just curious since that's always been stated as the only reason not to buy them. Sorry replied to wrong thread. Duh
06-26-2013 08:16 AM
Neil F.
Quote:
Originally Posted by Fa310tx View Post
Thanks for the info.
I thought you could adjust the speedo, but I never knew how.
Does the tach need adjusted any, with gearing and tire differences, or would the RPMs be accurate?
JJ
The tach reads whaever the engine is actually turning. The engine is mechanically coupled to the drive train. Changing the wheel size and or gearing impacts what the engine is running whan moving.
06-26-2013 06:51 AM
scgeek12 Here is a pretty cool youtube video that hits on gear ratios a little bit-

How a Differential Works and Types of Differentials - YouTube
06-25-2013 10:15 PM
Lando25
Quote:
Originally Posted by Fa310tx View Post
Thanks for the info.
I thought you could adjust the speedo, but I never knew how.
Does the tach need adjusted any, with gearing and tire differences, or would the RPMs be accurate?
JJ
Tach is fine, its measuring the rotation of the motor not the transmission or axles.
06-25-2013 09:36 PM
Fa310tx
Quote:
Originally Posted by muherd50 View Post
fa310tx,
You need to change the speedo gear in your TC if you're sure your speedometer is off. Search for a chart that tells you the right size speedo gear (teeth count) for your tire size/gear ratio.
Thanks for the info.
I thought you could adjust the speedo, but I never knew how.
Does the tach need adjusted any, with gearing and tire differences, or would the RPMs be accurate?
JJ
06-25-2013 08:05 AM
muherd50 fa310tx,

You need to change the speedo gear in your TC if you're sure your speedometer is off. Search for a chart that tells you the right size speedo gear (teeth count) for your tire size/gear ratio.
06-24-2013 11:37 PM
Lando25
Quote:
Originally Posted by Teague242 View Post

That upshift light is completely useless unless your on flat ground. Don't pay any mind to it.
Even when my jeep was completely stock I couldn't shift at the preset points, and retain any momentum going up a slight incline.
A lot of people take the bulb out or just put tape over the idiot light. Its useless...
06-24-2013 11:07 PM
Teague242
Quote:
Originally Posted by Fa310tx View Post
Does changing the gearing and tire size effect the RPM reading and shifting points?
I'm geared to 4.56 with 36" tires.
I noticed my speedometer is about 10-15 mph higher than my actual speed.
I also noticed that my upshift light comes on at odd times (sometimes it will come on at 2000 RPM and then go back off as I go higher (doesn't really make sense to me).
JJ
That upshift light is completely useless unless your on flat ground. Don't pay any mind to it.
Even when my jeep was completely stock I couldn't shift at the preset points, and retain any momentum going up a slight incline.
06-24-2013 11:03 PM
Fa310tx Does changing the gearing and tire size effect the RPM reading and shifting points?
I'm geared to 4.56 with 36" tires.
I noticed my speedometer is about 10-15 mph higher than my actual speed.
I also noticed that my upshift light comes on at odd times (sometimes it will come on at 2000 RPM and then go back off as I go higher (doesn't really make sense to me).
JJ
06-24-2013 01:11 PM
jquinn83 Thanks for this thread I learned a lot. Jerry is like an Encyclopedia Jeep!
06-24-2013 12:55 PM
Jerry Bransford
Quote:
Originally Posted by Gily View Post
I bought 5.38 from northridge 4x4 last week and the called me and told me it was better to have 5.12 for 35" and I switched to 5.12, I should get them next thursday.
I wouldn't have changed the ratio, 5.38 would be ideal. Sales reps rarely know what they are talking about when recommending ratios & it is rarer yet for them to know the .69 Overdrive issue the 42RLE has which makes a lower than usual ratio advisable.
06-24-2013 12:07 PM
Dextreme I know this thread has a few twists-n-turns (pun not really intended), but one consideration that hasn't been mentioned yet in this thread is the "size of the axle". A d44 with 33", will have more ground clearance than and d60 and 33"s, so many opt to not go with d60's and instead build strong d44's and stick with 33"-36" tires.
06-24-2013 11:45 AM
flash1034 I ran 5.38 s in my JK Rubi with 35s and it was perfect. I recommend you do he same.


Flash
06-23-2013 10:36 PM
Gily I bought 5.38 from northridge 4x4 last week and the called me and told me it was better to have 5.12 for 35" and I switched to 5.12, I should get them next thursday.
06-23-2013 07:58 PM
Jerry Bransford With your automatic 5.38 will barely be low enough for 37" tires but that ratio would be absolutely perfect for 35" tires. Regearing is probably going to be pretty close to $1300-1500 for all parts & labor. I got my last regearing done for just under $1100 but that was only after some serious negotiating.
06-23-2013 07:51 PM
Gily 3.8, Auto, rubicon Dana 44s
06-23-2013 07:50 PM
Gily
Quote:
Originally Posted by Jerry Bransford View Post
What engine, transmission, and axles do you have? D30 up front?
3.8L, auto, Dana 44s both Rubicon
06-19-2013 09:24 PM
Jerry Bransford
Quote:
Originally Posted by Gily View Post
Thanks, I just ordered a package fron northridge 4x4 with front and rear yukon gears 5.30 and installation kit, how much do the installation run?
What engine, transmission, and axles do you have? D30 up front?
06-19-2013 08:15 PM
Gily Thanks
06-19-2013 08:13 PM
Gily Thanks, I just ordered a package fron northridge 4x4 with front and rear yukon gears 5.30 and installation kit, how much do the installation run?
06-19-2013 08:08 AM
Happy JK Also you want the front and rear gear to match, so if you do regear it would have to be both axles. Otherwise you can't use 4wd, the vehicle would be fighting itself
06-19-2013 07:43 AM
UnlimitedRubicon
Quote:
Originally Posted by Gily View Post
Is 5.38 good for 37's? Which gears need to be chsngef?

Yes. Both, if you want to use 4 wheel drive.


Quote:
Originally Posted by Gily View Post
How much will the regear cost?

A lot.


Quote:
Originally Posted by Gily View Post
WhAt geAr brand is the best?

Whichever brand your installer sells and will stand behind.
06-19-2013 07:13 AM
Gily WhAt geAr brand is the best?
06-19-2013 07:12 AM
Gily How much will the regear cost?
06-19-2013 07:12 AM
Gily Is 5.38 good for 37's? Which gears need to be chsngef?
06-18-2013 08:25 PM
Jerry Bransford
Quote:
Originally Posted by freeskier View Post
Of course there are many real world factors to consider, it's just a general rule when speaking of cars across the board. Most vehicles aren't underpowered bricks with large tires driving down the road.
We're talking Jeeps, not cars here.
06-18-2013 08:21 PM
freeskier
Quote:
Originally Posted by Jerry Bransford View Post
It is not necessarily true that a numerically higher axle ratio number (lower ratio) will lower your top speed & visa-versa.

Running too high of a ratio can reduce your top speed which means going to a lower ratio can increase your top speed. For example if you were running 3.07 gearing & increased your tire size to 35", you'd barely be able to maintain a legal speed on the highway. Going to a lower ratio will raise the engine rpms in that case which will increase power & thus the top speed.
Of course there are many real world factors to consider, it's just a general rule when speaking of cars across the board. Most vehicles aren't underpowered bricks with large tires driving down the road.
06-18-2013 08:10 PM
AC0QR
Quote:
you'd barely be able to maintain a legal speed on the highway.
Not necessarily true. You could maintain legal speed on the highway, but might have to stay in 4th or 3rd to do so.
06-18-2013 08:01 PM
Jerry Bransford
Quote:
Originally Posted by freeskier View Post
Numerically high gear ratios provide better acceleration because you have more torque at the wheels for any given RPM, but lowers your top speed. Numerically low gears are the opposite, raise your top speed but hurts your acceleration.
It is not necessarily true that a numerically higher axle ratio number (lower ratio) will lower your top speed & visa-versa.

Running too high of a ratio can reduce your top speed which means going to a lower ratio can increase your top speed. For example if you were running 3.07 gearing & increased your tire size to 35", you'd barely be able to maintain a legal speed on the highway. Going to a lower ratio will raise the engine rpms in that case which will increase power & thus the top speed.
06-18-2013 07:55 PM
freeskier Gear ratios are considered your final drive ratio, as said the lower the gearing (numerically higher) gives you more revolutions of the driveshaft compared to the tires. This is also a torque multiplier, in 4wd low the number can be pretty astounding.

Numerically high gear ratios provide better acceleration because you have more torque at the wheels for any given RPM, but lowers your top speed. Numerically low gears are the opposite, raise your top speed but hurts your acceleration.

In the world of off road you want torque.
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