Twofourflinching
New member
Did not have the funds to upgrade gearing to 4.56 so i am stuck with 3.21 for a few months. Planning on going to dunes for a couple trips in Jan. What should i expect? Will be in 4 hi and low.
2014 JKU with 3.21 and 35s
- Thread starter Twofourflinching
- Start date
Who makes a 34" tire? Or, are you saying that you have metric tires that have a true measurement of 34"? If the later, you do know that an advertised 35" tire has a true measurement of only about 33", right? You really need to be looking at 4.88's. If you had a Dana 44 front axle, I would go so far as to run 5.13's.
Twofourflinching
New member
Not very knowledgable about gears so pls keep the flaming to a minimum. Won't I be using higher gears in sand? I thought keeping the wheels spinning in sand would not be too bad. Hate to have a worthless rig in Glamis. I thought gearing 3.21 would be bad for crawling, not in sand.
Gears are just part of the equation. What size tires will you be running with them is the other?
Twofourflinching
New member
I am running general grabber 315s, diameter is 34.4 and they weigh in at 64lbs each.
And that's my point. Most 37" tires have an actual measurement of about 35" and your tires are closer to that than anything. To bring your Jeep's on-road performance back to about stock with this size tire, you would want to be running a set of 4.88s. For a set of advertised 35" tires will have an actual measurement of about 33", 4.56 would get you to about stock performance again. Of course, when I say stock performance, I'm talking about what you'd feel with a set of 3.73 gears and 32" tires or perhaps in your case, a 3.21 gears with a set of 28" tires. What you felt back then will be greatly diminished with a significantly bigger set of tires.
You ever ride a 10-speed bike in the highest gear where cruising down a flat road is almost effortless? Leaving it in that gear, how much effort does it take to get that bike going from a stop? You motor will feel the same way with your 37ish tires and 3.21 gears.
You need to be turning your wheels first before you can keep them spinning.
jmatta33
New member
that might possibly the best analogy explaing how gearing works that I've ever heard...
Twofourflinching
New member
Thanks. Looks like I am going 4.56
Jk909
New member
Yes Eddie They are metric so they measure 34. I didn't know that 35's only came out to 33". I'll definitely take your advice on the 4.88. My jeep is a dog right now. 5th gear doesn't even exist.
jmatta33
New member
just out of curiosity, how are you measuring them? there is some miss information out there about the proper way to measure tire height.
IBeHeWhoIsJoshua
Caught the Bug
3.21 is a horrible ratio...even when I had the street fighter tires from the stealership. When I got Rubi take off tires it was annoying and I should have got a tuner to adjust for the tires. When I went to the 35" Nitto's back in March or so of this year I started using my automatic like a manual. Yes I lost 5th unless I was flying down a hill but it did make the Jeep drive able. About a week ago I finally got a flashcal and I was shocked at what a difference that thing makes. I read a couple different threads on here before tuning, about how to measure the tire properly and yada yada. I can actually drive around in automatic mode again! I still find it best to lock it out of 5th on the highway though. I am also running 25 cold psi. Normally I am at 28 cold psi. Now, I have also had 37's on my rig and will again in about a month. I'll lose 4th too until I regear. 37's have been my plan all along and since I do a lot of street driving I'll be going with 5.13 gears and a Detroit locker in the rear. Hopefully I'll be able to regear before a couple good runs this year. After all my rambling, get a flashcal, run proper air pressure (much less then 35), and enjoy some bigger tires. Regear when your bank account lets you.
LOL!! With your 37ish tires? Have fun with that.
Honestly, 5.13's would be a better ratio but, if you have a Dana 30, that will leave your pinion really small so 4.88 would be the smarter way to go.
This is true. Best way is to measure from the center of your wheel to the ground and x2.
Jtmw
New member
LOL!! With your 37ish tires? Have fun with that.
Agreed, ran 37's on 4.56. It's no 35s on 3.21 but definitely not great. Had an Atlas II to make up the difference.
Just so that it's clear for everyone else here, that's an advertised 35" tire as in, that's what it says on the sidewall but has an actual measurement of about 33", right?
4.88 gears with advertised 35's and with a 3.6L motor is a good combination that will bring you back to stock performance. :yup:
Yeah, I'm running 37x12.50's now (actual measurement of 35") and tested them out with 5.13's and thought it was a perfect match. I am now testing them out with 5.38's and, while the extra power is nice, the ratio is probably a bit on the high side. It sucks that it costs so much to swap gears but, I may go back down to 5.13's someday. You just don't know for sure until you've tested things out and I needed to know for myself what things would be like on a 3.6L vs. a 3.8L.