3.73 gears and 37"s

[Scruf]

Looking through the forum, I see there are some who have 37"s on a Sport or Overland with 3.73 gears. I'd like to hear their comments on driveability... general acceleration, towing, fuel economy, etc.

On the hwy, does it constantly jump in/out of 8th gear? I think I'd prefer that it not shift into 8th vs constantly jumping between 7/8 gear.


As a comparison, if with stock 32"s at 76mph it's turning 2000 rpms in 8th, then with 37"s in 7th gear, it would be turning 2169 rpms. That actually wouldn't be too bad.


As another interesting comparison, if you look at the final drive numbers (transmission gear ratio * differential gear ratio), the 8spd auto with 3.73's is very similar to the old JK 6spd manual with 4.56 gears (plus you get 2 more overdrive gears).

JK Manual	JK Final	JT Auto	JT Final
4.46	20.34	4.71	17.57
2.61	11.90	3.13	11.67
1.72	7.84	2.10	7.83
1.25	5.70	1.67	6.23
1.00	4.56	1.28	4.77
0.80	3.65	1.00	3.73
4.56		0.84	3.13
		0.67	2.50
		3.73

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[Jt-wrx]

It sucks, i have them on a 6-speed manual. It's fine around town and mostly empty running. It's actually good for that. As soon as you load it, offroad, steep hill, trailer backing up onto a curb etc. you will need 4 lo.

I can run 5th gear at about 2250 rpm at 123 km/h (between 75-80 mph). In town it's just a 4 speed until you hit the highway. 6th gear 100% useless.

I've had a helluva wait for 4.88's, 4wp got them in from yukon gear and they got rubicon rebuild kits, tore my shizzo apart a few weeks ago after a lengthy wait to get it in to begin with and had to put back together same day. Still waiting for this. Sure hope everyone gets their poop in a group. I want to tow more as summer approaches. Have to say my 4wp experience hasn't been spectacular.

 

[Scruf]

Thanks for sharing your experience with the 6spd manual. The gearing between the 6spd manual and the 8spd auto is a bit different, but still an interesting comparison.

The manual has a steeper 1st gear but for the rest, the 8spd is a little deeper, and you get more gears.

But it definitely confirms that 8th gear in the auto wouldn't be very usable. (worse that your 6th gear). Your 5th gear would be similar to the 7th gear in the auto. So when you're turn 2250 rpms, the auto would be 2332 rpms.

JT Manual	JT Final	JT Auto	JT Final
5.13	19.13	4.71	17.57
2.63	9.81	3.13	11.67
1.53	5.71	2.10	7.83
1.00	3.73	1.67	6.23
0.81	3.02	1.28	4.77
0.72	2.69	1.00	3.73
3.73		0.84	3.13
		0.67	2.50
		3.73

 

[Jt-wrx]

the auto will turn less rpm in 8th than the 6-speed in 6th, the auto is more flexible and tolerant so that's why the 4.10 auto's do well, it still waaay better for those who've gone to the 4.88's on the auto's with 37's, like driving it off the lot better, lots of pop, transmission and gear sorting which fca does such a great job of is back to normal

studied it to death, 4.88's are the winner either transmission for 37's, guys with the auto's get a nice 2400 rpm at 80 in 8th, their mileage gets back to normal etc. the 6-speed and auto are similar enough, the 6-speed in 6th should be 2400 at 75 mph...and on 37's you'll need that rpm to maintain well in wind/most rolling hills, 2250 i can tell you is only enough for one or the other, bit of headwind or rolling hills, not both, need a couple more hundred rpm for both

And my build is light, i'm only 5150 lbs all up full of gas and my gear without me in it. The heavy rigs will want to be another hundred or two rpm higher to maintain. And if overlanding/crawling/wheeling for a heavy rig is in order then 5.13's may well be the hot ticket.

 

[Mr. Wuf]

I just switched to 37s on my Overland and installed a Tazer to calibrate the speedometer. I’ve only had them for about 50 miles, but so far it’s not as bad as I was prepared for. I still want to go to 4.88, but my Jeep is absolutely drivable in the meantime.

 

[sage9984]

I just switched to 37s on my Overland and installed a Tazer to calibrate the speedometer. I’ve only had them for about 50 miles, but so far it’s not as bad as I was prepared for. I still want to go to 4.88, but my Jeep is absolutely drivable in the meantime.

Which 37's did you go with? Do you have a auto or manual?

 

[Jt-wrx]

as i mentioned, it's not bad on the street, wait till you have to test it in stuff that will drag on the tires, mud/steep hill starts from a dig/snow/trailer....it's totally acceptable and fine on the street running essentially empty...the auto more so than the manual, the auto may hide the work it will be trying to do to compensate but it needs to work so much harder without re-gear on 3.73's, this i know from seeing what happens with the manual transmission, you can't hide the extra work with the manual

 

[Mr. Wuf]

Which 37's did you go with? Do you have a auto or manual?

I went with Ironman All-Country MTs. They were $750 to my front door for four tires. I couldn't find a better deal anywhere. When I measured them on the Jeep, they measured out to right at 35.75", but I really like the Jeep's stance now.

I drive an auto.

 

[sage9984]

I went with Ironman All-Country MTs. They were $750 to my front door for four tires. I couldn't find a better deal anywhere. When I measured them on the Jeep, they measured out to right at 35.75", but I really like the Jeep's stance now.

I drive an auto.

That's real cheap. I'm looking at nitto 37*11.5*18 ridge grappler for 1200 shipped to my house. Did you regear? I'm in a 6spd.

 

[Mr. Wuf]

I used tirebuyer.com. They had a Facebook ad for 7% off their listed price, and the Honey browser extension I use with Chrome found a deeper discount (8%, I think.)

I haven’t regeared yet, but I plan to fairly soon. Like I said, the Jeep is drivable, but I can absolutely tell I’ve lost a good bit of power. It feels gutless, like an old 2.4L TJ.

Rubitrux quoted me $2,000 for ARB gears and $1,800 for another brand whose name escapes me. They’re nearly 5 hours away but are right down the road from my sister-in-law’s house. I know they do excellent work, so I may still use them, but I plan to see if there’s an off-road shop closer to home that will do my gears for the same or less.

 

[Scruf]

I used tirebuyer.com. They had a Facebook ad for 7% off their listed price, and the Honey browser extension I use with Chrome found a deeper discount (8%, I think.)

I haven’t regeared yet, but I plan to fairly soon. Like I said, the Jeep is drivable, but I can absolutely tell I’ve lost a good bit of power. It feels gutless, like an old 2.4L TJ.

Rubitrux quoted me $2,000 for ARB gears and $1,800 for another brand whose name escapes me. They’re nearly 5 hours away but are right down the road from my sister-in-law’s house. I know they do excellent work, so I may still use them, but I plan to see if there’s an off-road shop closer to home that will do my gears for the same or less.

Where are you located? I graduated from NCSU btw.

 

[Mr. Wuf]

Where are you located? I graduated from NCSU btw.

Oh yeah? What year?

I grew up in Lexington, graduated from NCSU in ‘04, spent a year and a half in Kenly, and have been in the Kinston area ever since.

 

[sage9984]

Goblex in NJ is @$999 for any size gear.

 

[sage9984]

Maybe we can get a group buy of some sort

 

[Scruf]

Oh yeah? What year?

I grew up in Lexington, graduated from NCSU in ‘04, spent a year and a half in Kenly, and have been in the Kinston area ever since.

No way! I'm from Kinston. My parents still live there. I graduated from NCSU in '07 (i think, there years are starting to run together, haha). Your profile says you work in school administration. Do you work for one of the schools in Kinston?

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