fitzz47

I have a 2013 with 3:73 and auto.I'm happy around town,and on a recent 500 mile trip I averaged 21.2 miles a gallon at 70 mph. If I went 75mph it dropped to 17. For around town this is a great gear.I run about 23-2400 rpm @70mph. I have the 255/75/17 tire

rob_engineer

Others know the details better than me but you simply can't compare pre-2012 gear ratios with 2012-2013 ratios. In other words 3.21 on one is not the same as 3.21 on the other. Has to do with the total driveline. I'm sure someone who knows the details will chime in. There are lots of threads about the 3.2- vs 3.73 ratios. I would have to say over 90% of opinions is that the 3.21 is great if its only a mall crawler. Any more than that you should get the 3.73. I would say if you have any consideration of towing I would insist on the 3.73. In fact, I would get he max tow package which has the sway control programmed into the computer. There is no way to get that except when new from the factory. I have the 3.73 with max tow package. See my avatar for the trailer I successfully tow. Loaded it weight over 4,000 pounds.

fitzz47

Your right the new auto trans will change rpm's I have the max tow package as well doesn't your owners man limit towing to 3,500 lbs. max?

rob_engineer

Your right the new auto trans will change rpm's I have the max tow package as well doesn't your owners man limit towing to 3,500 lbs. max?[/QUOTE]

3500 pounds yes. I researched this to death and posted about it before. Most other countries official jeep websites rate this exact same gas powered jeep at 4400 pounds or higher. The low rating in the US most likely has to do with the fact that the top will not protect the occupants in the event of a crash. Reference U-hauls policy to not rent trailers to soft top jeeps. Another factor to consider. The Jeep liberty with smaller, lighter frame and less powerful engine is rated for 5,000 pounds. I have put a couple thousand miles towing my trailer. Of course I use all precautions such as dual axle brakes with brake controller, weight dist hitch and friction sway control device. It tows great but does bring the MPG down to about 11.

johnrb3b

Two major considerations.

If you want the 6 speed, manual transmission, then don't get the 3.21 axles.
Even with the better Pentastar engine, you still have a poorly matched set of gear ratios - 1st gear (4.46:1) and the 3.21 axles.

The issue is startup from a dead stop, which is made worse if you're on a hill.
1st gear is simply NOT low enough for good, easy clutch action with 3.21 axles. It should be closer to 6:1. I believe that 1st gear must have been designed to match with the 4.10 axles of the Rubicon.

Yes, many of us have that combination, even with bigger than stock tires, and live with the need to carefully balance throttle and clutch at startup. If you're not skilled at driving a stick shift, you will either kill the engine at startup or over-rev and slip the clutch, resulting in short clutch life. A clutch, properly driven, should last the life of the vehicle. I've driven vehicles up to 150,000 miles and the original clutch was still fine.

My JK with 3.21 axles is simply a pain. I can drive it fine, but I have to actually pay attention to what I'm doing with the clutch at startup instead of letting 50 years of muscle memory do it for me.

Any responses from people with automatic transmissions are not relevant to your question. Stick shift people only can tell you what's up with the 3.21 axles.

When my stock tires wear out, I'm re-gearing to 4.10 and tires that are just under 32". That will give me much better balance between 1st gear and the axles and still give me a comfortable 75 mph on the highway at well under 3,000 RPM.

TheTerminator

For the manual transmission, the output gear ratio is the same. The only difference is the more powerful engine. For auto the output gear ratio is different (lower), because of the new tranny with lower gearing.

Flip94ta

I ordered mine with 3.73's and kinda regret it, 2400rpm at 70 is overkill, I think I'd be happier and richer with the 3.21's. It's been touched on many times before that you can easily run 33's with a Pentastar and either transmission. If heavy towing or high altitude is a factor go with 3.73's.

Also, I must admit that i think post about 3.21's not being matched to the 1st gear of the six speed is crazy. 4.46 is one of the lowest first gears available and is very generous to the offroad set.

SumoSizeit

I'm tipping in favor of the 3.73s...

A few reasons:

• Stock axles are probably more durable than I think they are, and can likely stand a minor tire size increase for mud and sand wheeling
• If I'm towing, it's in the mountains and hills more than anything
• It's only $95 more, and gas savings from highway cruising at lower RPMs are probably insignificant given my 6 speed and suburban commute.

rob_engineer

I've been on this forum for almost a year. I can honestly say I think this is the first time I heard someone say they wish they had gotten the 3.21 gears.

CliffCrawler

Actually used 3.21 climbing red cone pass with 35s. Yes! You better have some experience... The truth, I don't haul with my JK... That's what's an old pickup is for. 90$ more, no brainier and get the 3.73s or you'll be thinking this thread. Then it's JK after Jk.... Save the headaches