What would be the best gear ratio for a daily driver?

MrMark52

MrMark52

TJ Enthusiast
Joined
Jul 24, 2019
Messages
325
Location
North Texas
At 130k miles, our 2003 TJ (Oreo) is due for some differential work. I’m a novice on gear ratios - hoping for some good recommendation -

Oreo has the 4.0l I6, 42RLE tranny, lockup torque converter LSD differential, running stock wheels and tires (P225/75R15’s @ 28.3” diameter). Stock gearing is currently 3.73. Use is as a daily driver/mall crawler/toad (we tow behind our MoHo). Being retired, we just use to cat around town.
We live in the flat part of Texas with occasional trips to the Hill Country, and Colorado, and Florida.

Have had one shop recommend moving to 4.10 gear ”as 3.73’s are getting harder to find”. I know the rear needs to be retired as she whines, and after a 10 mile highway drive, she sounds like she’s crunching teeth. I did buy and have sitting in the driveway a used 3.73 from a ‘97 that I also have all the parts needed to upgrade to ABS (me likes my ABS). I just haven’t had time to “do the swap”.

Front needs new shaft seals/u-joints, and very likely all 4 ball joints as the chamber is 1/2 degree out on passenger side. Possibly track bars as well (stabilizer replaced 3 years ago).

Looking for recommendations from those smarter than I when it comes specifically to TJ’s and the drive train set-up under the hood. She’s lived in the Texas/Oklahoma region all her life so she’s a good solid bucket - and considering what a newer used one would cost - I think I can do the work and still be ahead in $.

TIA!
 
If you're happy with the way the thing drives now, and you have no future plans for lifts or big tires, I'd say stay with the 3.73's. As for 3.73's being hard to find, if the gears are set up properly, you'll likely not have to worry about that again in this lifetime.
My '03 with the 3.73's has almost 200k miles on it and is still going strong.
 
Old_Crow said:
If you're happy with the way the thing drives now, and you have no future plans for lifts or big tires, I'd say stay with the 3.73's. As for 3.73's being hard to find, if the gears are set up properly, you'll likely not have to worry about that again in this lifetime.
My '03 with the 3.73's has almost 200k miles on it and is still going strong.
Click to expand...
Thanks! It seems to shift into overdrive a tad early and the mileage isn’t near what I would like (realizing TJ’s aren’t known for good mileage) - but since I‘ll be taking the dive, I thought I would ask what others thoughts were on what ratio.
As noted originally, I’m a novice at gear ratios vs. tire size vs. engine performance. I feel experience of those on the board is better than guessing on my part. 😀
 
Obi-Wan said:
Harder to find?
Who is this mechanic and why do you listen to him?
Click to expand...
Thanks!

Not sure what point that your trying to make here.

Who I have gotten a quote from and why he said what he said is why I posted the question here. I can only assume you don’t agree, and that’s OK - but your reply doesn’t provide any insight or answer to my original question.
 
MrMark52 said:
Not sure what point that your trying to make here.
Click to expand...

The point I'm making is that if a shop recommends that you get 4.10 gears because 3.73's are "hard to find", then he doesn't know what he's talking about.

MrMark52 said:
running stock wheels and tires (P225/75R15’s @ 28.3” diameter). Stock gearing is currently 3.73. Use is as a daily driver/mall crawler/toad (we tow behind our MoHo). Being retired, we just use to cat around town.
Click to expand...

3.73 on stock tires is a perfectly acceptable gear ratio for this setup. Here's a comparison at 2000RPM of the difference in speed using 3.73's vs 4.10's

3.73.JPG
4.10.JPG
 
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Obi-Wan said:
The point I'm making is that if a shop recommends that you get 4.10 gears because 3.73's are "hard to find", then he doesn't know what he's talking about.


3.73 on stock tires is a perfectly acceptable gear ratio for this setup. Here's a comparison at 2000RPM of the difference in speed using 3.73's vs 4.10's

View attachment 322850View attachment 322851
Click to expand...

Thank You!

Not defending the shop I got the Quote from, just repeating what he wrote to me when he provided the Quote. I came to this site to confirm his “opinion”, and between your and others replies, it sounds like he is misinformed (or maybe has some 4.10’s laying around that he could move off his shelf to some unsuspecting buyer)..
I will say this is a rather well known shop in the DFW area whose primary work is advertised to be Jeeps.

I‘ll play with the calculator after finding the torque curves for the 4.0l. Would like to see how the gearing aligns with the engine’s “sweet spot”.
 
4.10's might be a tad better for 30-31" wheels, that's when you start to notice 3.73's fallin short. stock wheels i wouldn't bother.
i could see the supply chain shortages making a very popular gear ratio harder to locate. but you can find stock axles for less than what that regear for 1 end would cost, might just have to take a drive to get um.
 
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MrMark52 said:
Thanks!

Not sure what point that your trying to make here.

Who I have gotten a quote from and why he said what he said is why I posted the question here. I can only assume you don’t agree, and that’s OK - but your reply doesn’t provide any insight or answer to my original question.
Click to expand...

point is that 3.73's are not hard to find, try another shop.
 
someguysjeep said:
but you can find stock axles for less than what that regear for 1 end would cost, might just have to take a drive to get um.
Click to expand...
This is exactly what I did. I found a stock Rubicon 44 and Dana 30, with Detroit True Trac (4.10), for less than the cost of a re-gear. The difference between the previous 3.73 and 4.10, on my 31" tire build, was unnoticeable.

Edit: I also figured out that I could go to a 5.13 gear, with the .69 OD, on 31" tires (true size of 29.7) and only run 2800 rpms at 70 mph ;)
 
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csaxj3 said:
point is that 3.73's are not hard to find, try another shop.
Click to expand...
I clearly understood his response - a response that was not in any way helpful in light of the original question.

Obi-Wan did later respond with some insite and helpful knowledge which is what I think is what the purpose of this board, or at least the forum and thread, is for. Not to be judgmental of others opinions without a full understanding of that persons perspective.

Now back to our regularly scheduled programming. 😀
 
Mark,
I went to 3.73 from 3.07, I wanted the 4.10s but was unable to find a set. I changed out the entire axle, which was the less expensive way to go for me. In my area at the time 4.10s we’re just not around.
I know the numbers tell us that there is not a big difference between 3.73 and 4.10 but in the “seat of pants feel“ for me there was a noticeable difference and I am still keeping a watch out for a set of 4.10s.
the local shops here wanted $5k for both gear sets installed, changing out the axles my self was straight forward and less than $500 with new bearings and seals.
 
MrMark52 said:
At 130k miles, our 2003 TJ (Oreo) is due for some differential work. I’m a novice on gear ratios - hoping for some good recommendation -

Oreo has the 4.0l I6, 42RLE tranny, lockup torque converter LSD differential, running stock wheels and tires (P225/75R15’s @ 28.3” diameter). Stock gearing is currently 3.73. Use is as a daily driver/mall crawler/toad (we tow behind our MoHo). Being retired, we just use to cat around town.
We live in the flat part of Texas with occasional trips to the Hill Country, and Colorado, and Florida.

Have had one shop recommend moving to 4.10 gear ”as 3.73’s are getting harder to find”. I know the rear needs to be retired as she whines, and after a 10 mile highway drive, she sounds like she’s crunching teeth. I did buy and have sitting in the driveway a used 3.73 from a ‘97 that I also have all the parts needed to upgrade to ABS (me likes my ABS). I just haven’t had time to “do the swap”.
Click to expand...
With the 42RLE 4.10 would not be a bad choice at all for the stock factory size tires, it would get rid of the drivability problems caused by it's extra-steep .69 Overdrive ratio that drops the highway cruising rpms so low. Maybe even give you slightly better mpg as my regearing did. But will you always be staying with factory size tires or do you see installing larger diameter tires with a suspension lift some day?
 
Jerry Bransford said:
With the 42RLE 4.10 would not be a bad choice at all for the stock factory size tires, it would get rid of the drivability problems caused by it's extra-steep .69 Overdrive ratio that drops the highway cruising rpms so low. Maybe even give you slightly better mpg as my regearing did. But will you always be staying with factory size tires or do you see installing larger diameter tires with a suspension lift some day?
Click to expand...
Thanks @Jerry Bransford! For as long as we will own her, she’ll stay stock wheels/tires.

You've hit the nail on the head with the low cruising rpm’s when in OD. When I get to a slight hill, adding accelerator doesn’t seem to gain much so she slips out of OD until I crest the hill and level out, then back into OD.

And remember I’m in Texas, so more flat than hilly or mountainous (our hills to a Californian are more like speed bumps unless you live in the San Joaquin valley).
 
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