Is 33s on a stock 2006 TJ with 3.73 gears asking for trouble?

billiebob said:
Drop a gear, Then tromp the pedal.
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The point is to have low enough gearing for off road and to not have to "drop a gear" or two whenever you are looking to pass. I could have simply used 4 out of 6 gears but, now I can use the Jeep as intended; have great low gearing while descending and climbing off road, and have to drop maybe one gear to keep my speed up while climbing on the hwy.
 
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Ok, here's the best argument that I can come up with for proper, meaning low enough, gearing. This is for my 2.5 manual SE and may not apply to other rigs.

Going on steep, tight trails I have to go into low range to be able to dodge the trees and rocks and still have the power to pull the slope. Walking speed up a steep hill, in other words. There just isn't enough torque at a low enough rpm to do it in 2x or 4hi. That's with 31" tires. I don't need 4x for traction, but I need 4lo for the gearing. The SE will happily tool around in 2nd or 3rd all day long. No issues. But I need the gears for the more technical stuff.

Make sense?
 
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My point is high enough gearing for 75mph on the interstate. 4LO will do everything I need on a trail. And being an old school ruck driver I have no trouble anticipating when to drop a gear or 2.

But the SE needs low gearing just to hit 60mph. Id also say the same for 35s or 37s with the 4.0L... all that extra mass will add stress. But for a DD on 33s with 4.0L.... and a clutch... if you pay attention 3.73 is a great ratio.

It is all about balance, power, load and your actual use. The only real reason for lower gearing is if you have not got enough lift to start from a stop in 1st gear.
 
LCL-Dead said:
Odd note: Nashorn's user ID# is 1775. I want it. (Yes, Semper Fi) :D

Much higher with O/D off, of course. Chugging around on base, when the OD kicks on in 4th gear, I scoot along at about 1500rpm @ 45mph. Given some of the explanations above I'm tempted to just turn the O/D off until I'm off base and can legally hit speeds above 50mph.

Here's my RPMs at speed.

View attachment 18737
View attachment 18738

The most surprising thing to me, of course, is that I managed to snag both of those pictures without either a check engine light or my "front lock" light blinking (Believed to be a wiring issue).
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Funny. Right now I'm debating on whether or not to enlist in the Corps. [emoji28]

Your RPM's are just a little lower than mine at the same speed. At 60mph, manual tranny, in 5th gear, with 3.73's, stock 28" tires, I am at 2,100 RPM's.

All these numbers and speeds that everyone is posting just seems to all be around the same..? So confused!
 
I think we're all smart enough to "drop a gear or 2". The thing is, the majority of us do not want to do so constantly. I had that 3.55 and 31" combination for 2 years and it was not good. Yes, I stayed out of 5th on the highway and it was fine, but it didn't fix the fact that all of my gears 1-4 were thrown off from the way the Jeep drove when it was stock. It was sluggish from stoplights unless I really wound it out and it still wasn't good.

There is simply no reason to have your gears set to the point where you cruise mostly in 4th only to use 5th rarely and only for the purpose of "dropping the rpm". If I could get 30 mpg by "dropping the rpm", then sure, I would. But it doesn't work like that. I get very similar gas mileage (1mpg higher) in my current 4.10 5th gear than I used to when the rpm was 600 rpm lower with 3.55, and now I have much more power to boot. I'll choose the lower gears. I'm about to regear to 4.88 on 33's with the 4.0 5-speed and I'm looking very much forward to not having to "drop a gear or 2".
 
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LCL-Dead said:
29.5", actually, just a hair larger than stock and according to the GPS app I use to track trails, the speedo is accurate to within 1-2mph.

Now you've got me worrying that maybe the gearing has been changed despite the 4.10 tag on the rear diff.

View attachment 18739
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Checking your speed with the GPS is a great way to know exactly what is going on. So many people up size tires and don't recalibrate for them and think they are going the speed on the dash.
 
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JP98 said:
Checking your speed with the GPS is a great way to know exactly what is going on. So many people up size tires and don't recalibrate for them and think they are going the speed on the dash.
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Haha, yep. I had a buddy who stuck 37" tires on his Chevy 1500 and was confused when he got pulled over for doing 67 in a 55.

"But I had my Cruise Control set at 60?!"
"That's still speeding son.."

I had to recommend that maybe he'd forgotten to recalibrate his speedo when he boosted the tires and so the officer let him off with a warning and directions to use GPS to monitor his speed.
 
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billiebob said:
My point is high enough gearing for 75mph on the interstate. 4LO will do everything I need on a trail. And being an old school ruck driver I have no trouble anticipating when to drop a gear or 2.

But the SE needs low gearing just to hit 60mph. Id also say the same for 35s or 37s with the 4.0L... all that extra mass will add stress. But for a DD on 33s with 4.0L.... and a clutch... if you pay attention 3.73 is a great ratio.

It is all about balance, power, load and your actual use. The only real reason for lower gearing is if you have not got enough lift to start from a stop in 1st gear.
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I could do 70 prior to the gear swap. I can still do 70 if I wanted but generally stick around 65 simply because it keeps my driving record ticket free for work. There are more benefits to lowering the ratio than taking off from a stop. Climbing grades on the hwy, crawling uphill, using the low gearing to go down steep grades off the brakes, etc. The ability to creep downhill on loose, technical terrain alone makes a gear swap a good idea. Get on the brakes in that shit and bad things happen. Having proper gearing means you don't have to constantly "pay attention to your gearing." If you are fine with your combo, great. But I can tell you, most do not feel the same way.
 
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4.0L, 5 speed, and 33's on 3.73's was what I was running for over a year. Got tired of feeling like I was leaving a stop sign in 2nd gear, and having to shift down to 4th on even the slightest of inclines to maintain freeway speed. Went to 4.56's, and shortly after took a trip to Moab for some wheeling, and OMG! My rig wheeled so much better! The steep drops on the slick rock and steep climbs, not to mention the negotiating of rock sections, where before, I'd always stall the engine, and after, not even once did I stall it. With the proper speedo gear change, I now feel like my jeep did when I bought it bone stock on 30's.
 
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5.13's are in the plan for those exact reasons. I'll fine tune the performance on and off road by running 31" or 32" tires. The 2.5 manual with 4.10/4.11 gears frankly sucks bilge water on 31" tires. No matter what you're doing or where you're driving, there isn't a "perfect" gear to select. Everything is just a hair to high or a hair to low. Does it work? Sure. There's always another gear or another range to go to. Optimal, not close.
 
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bobthetj03 said:
4.0L, 5 speed, and 33's on 3.73's was what I was running for over a year. Got tired of feeling like I was leaving a stop sign in 2nd gear, and having to shift down to 4th on even the slightest of inclines to maintain freeway speed. Went to 4.56's, and shortly after took a trip to Moab for some wheeling, and OMG! My rig wheeled so much better! The steep drops on the slick rock and steep climbs, not to mention the negotiating of rock sections, where before, I'd always stall the engine, and after, not even once did I stall it. With the proper speedo gear change, I now feel like my jeep did when I bought it bone stock on 30's.
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Now, if only you could figure out the driveline vibration. ;)

I've been checking your thread to see if it's been updated with any new attempts to isolate the vibration cause.
 
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Brantley said:
Now, if only you could figure out the driveline vibration. ;)

I've been checking your thread to see if it's been updated with any new attempts to isolate the vibration cause.
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That is the one word of warning I probably should give when re-gearing, and I have not isolated the cause of the vibes, so I can't comment on this being a common problem or not. Having replaced both drive shafts, gone thru the transfer case and installed a SYE, and adjusted pinion angles till I'm blue in the face, I can't determine if the vibes are drive line related or gear related. The drive shafts are spinning faster now, so something in my drive train system is not happy. More on this in my other thread as I continue to do stuff.
 
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Ok if I read correctly, for a 05 TJ. X .. 5 speed an yes I have 307 gears. I am running 33 X 12.5 15s. I need to regear to 4.56 also with gears I will need a (carrier)? Help me with that one please.. no rock climbing but some off road mud.. I read most on the comments but there is to much info for me to process..

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ffighter405 said:
Ok if I read correctly, for a 05 TJ. X .. 5 speed an yes I have 307 gears. I am running 33 X 12.5 15s. I need to regear to 4.56 also with gears I will need a (carrier)? Help me with that one please.. no rock climbing but some off road mud.. I read most on the comments but there is to much info for me to process..

Sent from my XT1650 using Tapatalk
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4.56 will work well with the 5 spd and 33's. You will need either carriers or thick gear sets.
 
ffighter405 said:
Ok if I read correctly, for a 05 TJ. X .. 5 speed an yes I have 307 gears. I am running 33 X 12.5 15s. I need to regear to 4.56 also with gears I will need a (carrier)? Help me with that one please.. no rock climbing but some off road mud.. I read most on the comments but there is to much info for me to process..

Sent from my XT1650 using Tapatalk
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How do you have an '05 with a 5-speed?
 
Brantley said:
How do you have an '05 with a 5-speed?
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Well I guess I am not sure how.. but it is setting in my garage. And I have 5 forward gears and 1 reverse gear. I thought that was a 5 speed..I am still learning about Jeeps...

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