I am Beginning to Fear the Gear - JeepForum.com
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post #1 of 48 Old 02-20-2019, 07:55 AM Thread Starter
Rick_Fury
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I am Beginning to Fear the Gear

I am beginning to "Fear the Gear" on my 1998 Jeep Wrangler. I have been driving it around on 32" tires with 3.07 gears and a 3-speed automatic for the last 12 years, and I am about to pull the trigger on 4.10 gears.

Tell me again that the 4.10 gear *is* the right choice. I will never go bigger than 33" tires.


While I am getting the axles re-geared, I am also getting the axles rebuilt. I am seriously considering adding a Detroit Tru-Trac to the rear axle as well. The rear axle is a Dana 35. All I ever really do is beach driving and back country roads for fishing; the axle will not be locked.

Will the deeper gears and limited slip add extra stress to the Dana 35?


This is going to be a BIG change. Is there anything else I should be aware of? Will I need to do anything to my transmission or speedometer?

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post #2 of 48 Old 02-20-2019, 08:51 AM
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Originally Posted by Rick_Fury View Post
Will I need to do anything to my transmission or speedometer?
You will need to change the speedo gear in the TC tail housing.
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post #3 of 48 Old 02-20-2019, 08:54 AM Thread Starter
Rick_Fury
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Originally Posted by biffgnar View Post
You will need to change the speedo gear in the TC tail housing.

It hasn't been changed all this time with 3.07s and 32" tires.


How much do you think it will it be off?
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post #4 of 48 Old 02-20-2019, 08:57 AM
2jhanna
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Just curious, what made you decide after 12 years?

How much longer do you plan on keeping your TJ?

I am multi-talented, I can talk and piss you off at the same time.

jhanna
denton county, tx
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post #5 of 48 Old 02-20-2019, 09:09 AM
Jerry Bransford
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Quote:
Originally Posted by Rick_Fury View Post
It hasn't been changed all this time with 3.07s and 32" tires.


How much do you think it will it be off?
You're going to regear? Why even consider not also doing the simple 5 minute speedometer gear swap to get your speedometer accurate again? http://www.4x4xplor.com/speedo.html

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post #6 of 48 Old 02-20-2019, 09:13 AM
wildman4x4nut
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Gear ratio calculator that will tell you what your RPMs will be in each gear and at different speeds. http://www.grimmjeeper.com/gears.html

Speedo gear calculator that helps decide which gear you need to recalibrate your speedo. https://www.quadratec.com/c/referenc...ar-tooth-chart

WILDMAN

Cle Elum, WA

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post #7 of 48 Old 02-20-2019, 09:13 AM Thread Starter
Rick_Fury
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Quote:
Originally Posted by 2jhanna View Post
Just curious, what made you decide after 12 years?

How much longer do you plan on keeping your TJ?

I bought my Jeep in 1999. I went college in it, took my Wife on our first date in it, took our honeymoon in it, and brought our baby back from the hospital in it. It has been a very reliable vehicle, and I can do most of the repairs myself. My Wife and I are both emotionally attached to it, so I plan on keeping it.


What made me decide? I put a 2" lift and 32" tires on it about 12 years ago, and planned to re-gear soon after. Since then, everything above kept getting in the way.
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post #8 of 48 Old 02-20-2019, 09:15 AM
Jerry Bransford
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Also, 4.10 would be my choice for 33's with your 3-speed automatic.
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post #9 of 48 Old 02-20-2019, 09:19 AM
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Quote:
Originally Posted by Rick_Fury View Post
I bought my Jeep in 1999. I went college in it, took my Wife on our first date in it, took our honeymoon in it, and brought our baby back from the hospital in it. It has been a very reliable vehicle, and I can do most of the repairs myself. My Wife and I are both emotionally attached to it, so I plan on keeping it.


What made me decide? I put a 2" lift and 32" tires on it about 12 years ago, and planned to re-gear soon after. Since then, everything above kept getting in the way.
I had 3.07s and 32s once. I got axles from a 4 cylinder with 4.10s for under $250. Best money spent with the 32rh auto.

Quote:
Originally Posted by jeepinmichguy_ View Post
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post #10 of 48 Old 02-20-2019, 09:24 AM Thread Starter
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Originally Posted by Jerry Bransford View Post
Also, 4.10 would be my choice for 33's with your 3-speed automatic.
Thanks for the link on changing the speedometer gear. I didn't realize it would be that simple.

Would 4.10 still be your choice for 32's, or 265/75R/16 tires?

What are your thoughts on the Detroit Tru-Trac? I have done fine with an open differential so far, but my carrier has to be replaced anyway, so...


Quote:
Originally Posted by TheBoogieman View Post
I had 3.07s and 32s once. I got axles from a 4 cylinder with 4.10s for under $250. Best money spent with the 32rh auto.
Great!

After all this time, I am used to the 3.07 gears with 32" tires combo. That is all I have ever known. What should I expect with the 4.10 gears?
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post #11 of 48 Old 02-20-2019, 09:37 AM
Jerry Bransford
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Quote:
Originally Posted by Rick_Fury View Post
Thanks for the link on changing the speedometer gear. I didn't realize it would be that simple.

Would 4.10 still be your choice for 32's, or 265/75R/16 tires?

What are your thoughts on the Detroit Tru-Trac? I have done fine with an open differential so far, but my carrier has to be replaced anyway, so...

Great!

After all this time, I am used to the 3.07 gears with 32" tires combo. That is all I have ever known. What should I expect with the 4.10 gears?
You can expect a very significant boost in overall performance and you might even get slightly better mpg with the higher engine rpms getting the engine operating more efficiently.

I had front & rear Truetracs in my previous TJ for maybe two years. They are great on slick or icy flat road or trail surfaces but they are pretty much useless for offroading on trails that are uneven enough so a tire on the Truetrac equipped axle gets lifted off the surface. I ended up replacing both Truetracs with lockers which made a night and day improvement offroad. I was stupid to have installed the f/r Truetracs against the advice of those who were more experienced at offroading at the time.

When you have a choice, buy American made.
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post #12 of 48 Old 02-20-2019, 09:55 AM Thread Starter
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Originally Posted by Jerry Bransford View Post
You can expect a very significant boost in overall performance and you might even get slightly better mpg with the higher engine rpms getting the engine operating more efficiently.
*That* is what I am counting on.

But I will not be used to the higher rpms. I'm afraid it might be too much of a change. That is why I am starting to "fear the gear."


Quote:
Originally Posted by Jerry Bransford View Post
I had front & rear Truetracs in my previous TJ for maybe two years. They are great on slick or icy flat road or trail surfaces but they are pretty much useless for offroading on trails that are uneven enough so a tire on the Truetrac equipped axle gets lifted off the surface. I ended up replacing both Truetracs with lockers which made a night and day improvement offroad. I was stupid to have installed the f/r Truetracs against the advice of those who were more experienced at offroading at the time.

My rear axle is a Dana 35 , so I have no plans for a locker. Nor do I need it for the type of terrain I have here in the South East.
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post #13 of 48 Old 02-20-2019, 10:05 AM
Jerry Bransford
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...But I will not be used to the higher rpms. I'm afraid it might be too much of a change. That is why I am starting to "fear the gear."
It doesn't matter that you won't be used to the new higher rpms right away. Of course the rpms will be higher from what you have become used to, that's the entire goal of regearing. Having gotten used to the excessively low rpms is not something you should even be raising as a concern.

You have to get over the fact that different vehicles, different engines, different tire sizes, and different transmission types all have their own ideal engine rpms. Rpms that are appropriate for a Dodge Magnum V8, a Toyota running small tires, etc. are going to be inappropriate for a Jeep running big tires.

Being "used to" the wrong rpms that are too low doesn't make them the right rpms. Stop worrying about doing something that is the right thing to do.
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post #14 of 48 Old 02-20-2019, 11:05 AM
Wheelin98TJ
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Rick, 4.10 is the right ratio for you.

To give you an idea how it will feel, 4.10 gives you 33% more torque multiplication than 3.07.

As for your fear of the gear, I think your newly rediscovered low end will help you get over that.
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post #15 of 48 Old 02-20-2019, 02:00 PM Thread Starter
Rick_Fury
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Originally Posted by Wheelin98TJ View Post
Rick, 4.10 is the right ratio for you.

To give you an idea how it will feel, 4.10 gives you 33% more torque multiplication than 3.07.

As for your fear of the gear, I think your newly rediscovered low end will help you get over that.

I remember when my Wife and I went to the mountains on our honeymoon, and my Jeep seemed to slow down. I was going up a mountain, and cars were suddenly passing me. I went to push the accelerator down, but it was almost on the floor already! I remember that I could only manage about 45 MPH until I crested the mountain.

Was that because of the gears?
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