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Old 09-04-2011, 03:06 AM   #1
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Gear ratios: 3.21 or 3.73?

I may have overlooked this in the 24-page 2012 info:

A Sport Unlimited 2012 with manual transmission: fuel economy vs. drivability??

I calculated that with 3.21 the engine is at 1750 RPM at 100 kph (62 mph) and with the 3.73 at 2100 RPM, each in 6th.

I may get a test drive, but do not know if manual will be possible and the test drive may be too short, anyways and I doubt they have both ratios available.

Would be interesting to hear your thoughts and experience, thanks!! If the 6th is drivable I tend to the longer ratio.

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Old 09-04-2011, 03:11 AM   #2
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Oh, I realized that with the 3.21 axle first gear reaches roughly 45 mph, assumed a redline of 6500 RPM? That is really a tall first gear!

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Old 09-04-2011, 03:26 AM   #3
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To tall. Way too tall. Were fitted simply to achieve the required fuel economy tests, which are only done at 50mph (80km/hr). At highway speeds the wind resistance is too much, at least in the old 3.8.

Personally if you have the option, I would go for the 3.73 or even 4.1's, if you ever want to upgrade to higher in the future (larger wheels for example) then you dont need to change the carrier (3.56 down use a different carrier to 3.73 and up).
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Old 09-04-2011, 06:48 AM   #4
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First who really redlines their Jeep. So far I still think I have gone too far at 4,000 during some semi-heavy acceleration.

2012 Sport S 2D manual here. I got 3.73. Because I am counting on one day dragging something behind it. Water toy, camping gear, motorcycle, nephew to school....

I never towed anything, so wanted the best power and safety margins for when I do. I also got the Sport S, with 17" wheels instead of standard 16". If I absolutely never planned on towing anything I would have seriously considered the 3.21. Also, they came with their max tow ratings. Looks like 3.21 are at 1,000 pounds, everything else 3500 I believe for your Unlimiteds. I'm stuck at 2,000 being 2 door.

If you mod and add heavier weight, bigger tires, anything, get the 3.73. If you plan on keeping stock and family daily driver, and you KNOW you will be doing such, then go with 3.21. If any doubt, get 3.73.

For fuel savings, it is not going to matter much either way. Again, for stock.
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Old 09-04-2011, 07:20 AM   #5
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When I first came upon this site a week AFTER buying my '11 Sport "S" I thought "OH KA-KA!!!" I've screwed up.

Mine came with 3.21's and I then had the dealership add a 2" receiver hitch. I have the 6spd and I have a boat.

Here's what I have found. With a light rig such as a PWC (1) or a skiff, mines a 14' Alu. w/ a 9.9 hp. 4 storke Yamaha on a standard trailer, I have zero problems pulling up any ramp. No issues up hills either.

I agree with "MyKII". With my desired uses, a 6 spd & 3.21's work nicely. Your milage may vary.

This really vehicle isn't a heavy hauler. I think if your looking to do some searious trailer hauling I'd be looking at something in a P/U. My opinion only.
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Old 09-04-2011, 10:00 AM   #6
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I'm looking at 3.21's over 3.73's for fuel economy...but I'm looking at an auto with the new tranny. If I had a stick, I would go with 3.73's.
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Old 09-04-2011, 10:02 AM   #7
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In a 2012, the 3.21s will be fine. But if you can get 3.73s, go for it. No good reason not to. But if you can't, don't beat yourself up.
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Old 09-04-2011, 11:49 AM   #8
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Thanks, very helpful comments!

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