Gearing recommendation for 2003 Rubicon with manual transmission and 35" tires?

R

Riddler6.7

Member
Joined
Jan 1, 2018
Messages
83
Location
US
Have a 2003 Rubicon 5spd on 35s and plan on doing gears soon. I see lots of recommendations for 4.88s and a few for 5.13s. Just wondering if anyone that has done 5.13s regretted it and wish they had done 4.88s. It's just a weekend vehicle and the most I would want to do is 70mph with 60 - 65mph being more the norm top speed. Looking at gearing calculators, I don't really see a downside to 5.13s for me. It would put my rpms around 2300rpms at 65mph and a couple hundred more at 70mph if the calculator is correct.

I won't be doing any hard core wheeling just trail rides for the most part and running around in town.


Sent from my SAMSUNG-SM-G890A using Tapatalk
 
FWIW, I am running 4.88 on 33s/5 speed. Very similar to 35s on 5.13. 75mph is roughly 3000rpm. I think it is a great combination even on my daily driver. If or when I move to 35s, I would want 5.13.
 
Last edited:
While my 2005 Rubicon is an automatic, I went with 4.88s with my 33" tires and while it probably would be perfect to 90% of people, I was that 10% where I felt like I should have went with 5.13 instead. The 4.88s have plenty of power, but with the 5.13 I would have had just a bit more oomph off the line, which I would have liked.

Being as you have 35" tires, there is no question about it, I would go with 5.13 gears over 4.88 for sure!
 
Chris said:
While my 2005 Rubicon is an automatic, I went with 4.88s with my 33" tires and while it probably would be perfect to 90% of people, I was that 10% where I felt like I should have went with 5.13 instead. The 4.88s have plenty of power, but with the 5.13 I would have had just a bit more oomph off the line, which I would have liked.

Being as you have 35" tires, there is no question about it, I would go with 5.13 gears over 4.88 for sure!
Click to expand...
You have that pesky 42rle. Seems like the deeper you can go the better to combat the OD.
 
I know this thread is about gearing for the 5-speed manual transmission, not the 42RLE automatic, but in view of some recent posts in this thread about the 42RLE here are my observations about axle gearing for the 42RLE and 35" tires:

When I purchased my '06 LJ with 42RLE and 35" tires it had 4.88 gears. OD was useless because it was geared "too tall."
,
The Grimm Jeeper gear calculator, the only calculator I could find that will easily allow inputs for specific transmissions, suggested that I should re-gear to either 5.13 or 5.38 for 35" tires.

My gear installer had a similarly equipped LJ with 42RLE transmission, 35" tires and 5.13 gears. I spent some time driving it and concluded that it was better, but not perfect. OD still needed to be turned off in many normal driving situations, but not as often.

I elected to re-gear to 5.38. After driving 1,000 miles in varying conditions, in my opinion 5.38 is the perfect axle gear ratio for a TJ/LJ with 4.0 engine, 42RLE automatic transmission and 35" tires. I have not had to manually turn OD off in any normal driving situation.

YMMV
 
  • Like
Reactions: jeep_boss
Mr. Bills said:
...

I elected to re-gear to 5.38. After driving 1,000 miles in varying conditions, in my opinion 5.38 is the perfect axle gear ratio for a TJ/LJ with 4.0 engine, 42RLE automatic transmission and 35" tires. I have not had to manually turn OD off in any normal driving situation.

YMMV
Click to expand...

Your experience reenforces my belief that one of the purposes of regearing is to restore the functionally of the final drive. One of the things I noticed with my 5 speed was the significant decrease in the amount that I needed to downshift. This made daily driving far more pleasant. The low take off speeds are actually very helpful for crawling during rush hour and on slow city streets. Of course, the lower gearing is also great off road. This is why I say there is no downside to low gears.

When I was deciding on which ratio, I decided that the normal top speed would be 75mph and that ~3k would be the rpm for that speed. I can go faster when needed, but the Jeep just gets noisy and unpleasant to be in. 65-70mph is the sweet spot for highway cruising with traffic.
 
Hmm, I would probably want a 4.88 for a 5spd on 35's. I have a 6spd Rubicon with a 5.13, which is perfect for me. I can do 80mph, BUT 75 is my absolute top speed, and I do my absolute best to not exceed this artificial limit.
 
That is the NV3550, correct? If so, plugging numbers into the calculator: 34" tire (true height) with 5.38's at 70 is 2700ish. Perfect for the 4.0.
With the Rubicon 44's, you are able to run the 5.38 as opposed to the 30/44 combo.
 
jjvw said:
You have that pesky 42rle. Seems like the deeper you can go the better to combat the OD.
Click to expand...

Yep, I agree! That OD is really annoying. It's not nearly as bad with the 4.88s, but it's still nowhere near perfect.
 
When my previous TJ still had its 5-speed I regeared to 4.88 for my 35's. I still consider that combination perfect for both the highway and offroad. IIRC it produced 2750 rpms at 70 mph which gave very good performance.
 
Thanks for the input guys. I'm leaning towards 5.13s. It would be a somewhat rare thing for me to be on the highway and 95% of the time I won't go over 60mph.

Sent from my SAMSUNG-SM-G890A using Tapatalk
 
  • Like
Reactions: Jerry Bransford
I’ll try to post up my rear axle calculator spreadsheet tomorrow when I’m at my computer. Better to figure it out than guess or take the opinion of others who may not drive the same as you.
 
Mike Jolley said:
I’ll try to post up my rear axle calculator spreadsheet tomorrow when I’m at my computer. Better to figure it out than guess or take the opinion of others who may not drive the same as you.
Click to expand...
The two recommendations given, (primarily) 4.88 and 5.13, weren't guesses. Especially 4.88 is by far the most commonly installed and recommended ratio for the combination of 4.0L engine, 35", tires, and 5-speed manual transmission for highway, around town, and off-road. The OP eventually offered that he won't be driving much on the highway so the ratio was bumped down slightly to 5.13. Those of us recommending ratios here aren't guessing.

And when a gear ratio calculator is needed, we use the Grimm Jeeper at http://www.grimmjeeper.com/gears.html as Jivw recommended above which gives the true engine rpm at various speeds no matter what transmission is installed.
 
Last edited:
  • Like
Reactions: ToddK and jjvw
The grimmjeeper calculator looks overly complicated to me. I prefer my tool since I have taken the time to list all of the gear ratios and common ratio choices. You can also see all of the options at a glance once you choose your transmission ratio.

Looks like I can't upload a spreadsheet but here is a screenshot, it's just math:
upload_2018-4-23_12-21-3.png
 
  • Like
Reactions: Alex01
Top Bottom
Back