Yep. Accurate numbers in, accurate numbers out. I always go 1/2" less tire size when entering numbers and do not have an actual measurement. Not perfect but fairly close.
4.56 or 4.88 gears?
- Thread starter TJJeepGirl
- Start date
Yep. Accurate numbers in, accurate numbers out. I always go 1/2" less tire size when entering numbers and do not have an actual measurement. Not perfect but fairly close.
You can nail it almost perfectly if you get a known speed and rpm. Plug the tire size in and keep changing it until you match your known speed and rpm and that will get you a near exact rolling radius.
One of my more common discussions with the locals about gearing centers around them telling me the GJ calculator is wrong and doesn't match what they see on their odometer and tach. The only variable that isn't 100% pure basic math of known quantities like gear ratios and transmission ratios, is the tire size. That means they don't understand that the horizontal tire size and or the numbers on the sidewall have nothing to do with the rolling radius.
Garbage in, garbage out.
OP
Sorry just seen your reply. I'm running 35x12.50x15 and went with 4.56 gears and live in Kentucky.
Sunder
TJ Enthusiast
I have 4.56 gears with a 3speed auto (and a Ford 8.8 rear).
35" tires in summer, and 33" in winter. (but would prefer 35" in winter too - it's just what I currently have).
I'm happy with my gear choice...although I often wish I went to 4.88 for even better acceleration. I do like this gearing with my 33" tires.
(I previously ran 3.07 with 33's, so this acceleration thing is a treat...)
I "use" acceleration much more often than "top end" speed. Keeping in mind that I live in an archaic "city" that doesn't have freeways or other proper infrastructure, so the only time I'm going over 60km/hr (40mph) is when I'm going out of town to the cabin or to a trail. Everyday commuting to work is sub 60km/hr.
Places with freeways for commuting may want to think differently.
I also drive conservatively...or within the safe means of my Jeep...and my gas mileage, lol.
So my rpms are "high" on the highway (3000-3300) around 100-110km/hr (60-ish mpg). I rarely feel the urge to drive it at 120km/hr (I'm guessing 70mph-ish). Even if my engine has no problem getting to that speed, I do not feel safe enough with my stability if I have to do any kind of emergency maneuver.
It's the stability that is the limiting factor for me, not the engine.
I also chose 4.56 over 4.88 because I was going to be swapping between 33" and 35" tires. However, if I could go back in time and/or just run 35", I might have installed 4.88's. But that's keeping in mind I am not speeding on the highway.
35" tires in summer, and 33" in winter. (but would prefer 35" in winter too - it's just what I currently have).
I'm happy with my gear choice...although I often wish I went to 4.88 for even better acceleration. I do like this gearing with my 33" tires.
(I previously ran 3.07 with 33's, so this acceleration thing is a treat...)
I "use" acceleration much more often than "top end" speed. Keeping in mind that I live in an archaic "city" that doesn't have freeways or other proper infrastructure, so the only time I'm going over 60km/hr (40mph) is when I'm going out of town to the cabin or to a trail. Everyday commuting to work is sub 60km/hr.
Places with freeways for commuting may want to think differently.
I also drive conservatively...or within the safe means of my Jeep...and my gas mileage, lol.
So my rpms are "high" on the highway (3000-3300) around 100-110km/hr (60-ish mpg). I rarely feel the urge to drive it at 120km/hr (I'm guessing 70mph-ish). Even if my engine has no problem getting to that speed, I do not feel safe enough with my stability if I have to do any kind of emergency maneuver.
It's the stability that is the limiting factor for me, not the engine.
I also chose 4.56 over 4.88 because I was going to be swapping between 33" and 35" tires. However, if I could go back in time and/or just run 35", I might have installed 4.88's. But that's keeping in mind I am not speeding on the highway.
Jay P
TJ Enthusiast
I have this same setup with a Dana 44 and also came from 3.07s. I’m on 33s and feel it would easily turn 35s. We run it at 40-60 mph max (usually) and it’s not bad. But I’m thinking 65mph+ would be an issue and at this point I’m hoping to trailer it to trails that are further than an hour out.
Sent from my iPhone using Tapatalk
Keep in mind those ratios are correct for you because you have the 3-speed automatic. Ratios correct for your 3-speed automatic are going to be way different than what would be correct for his 5-speed manual. Which would be way different if the transmission was the 4-speed 42RLE automatic.
It can get confusing when talking about ratios when we're not talking about the same transmission types.
OP
We will see how it does this weekend. I'm planning on driving a 6 hour trip one way on the interstate. I did have to put in a new front driveshaft to help with the small vibration I was getting. But I had it up to 80mph yesterday and it drove smooth as could be. I also took it wheeling this past weekend and crawled all over. I'm very happy with my 4.56 gears!
Glad you like them, 4.56 was the perfect choice for your 35's and 3-speed automatic transmission.
OP
Glad you like them, 4.56 was the perfect choice for your 35's and 3-speed automatic transmission.
I have the AW4 now. With the 3spd my rpms were way to high. I wasn't happy with it for daily driving.
She installed an AW-4.Glad you like them, 4.56 was the perfect choice for your 35's and 3-speed automatic transmission.
OK. Here's my 2 cents. I have two CJ's one with a built 350, turbo 400, and 456R/P, 3.8 atlas, and 38" tires, one with a 4.0, dana 300, 315 (35) tires, and 456R/P, I have had gear ratios from the stock 300 something to 410's, 456's. Also, I have a 97 TJ, 4.0, 231, auto and 35" tires. I replaced both front and rear axles that included 488 R/P's, it's been the best R/P ratio swap I've ever done. Granted, I don't commute in this jeep, but changing to 488's has been like a motor swap. It's made the jeep come to life.
Gears and axles swaps are expensive and most of us live with them for a long time so I think you are wise to do your research.
Good luck on your journey.
Gears and axles swaps are expensive and most of us live with them for a long time so I think you are wise to do your research.
Good luck on your journey.
MARC CROMER
Member
I am struggling with this decision also, since have no experience driving/riding in a re-geared jeep. I have 4.0L, 5speed, Dana 30 front and Dana 44 w/limited slip rear. I want to do more overlanding and off-road climbing at the destination. Not crazy climbing, but need to get to Rubicon and Moab soon. Unfortunately, just getting to the "high country" for camping/fishing requires 6-8 hours of road time. Not planning to buy a trailer or store it, but my jeep sees no action unless I have a trip planned. Also, will likely tow 800lb trailer. Thanks for suggestions on 4.56 vs. 4.88 in my scenario. (p.s., Going to place elocker on rear and leave front open although some say lock the front).
I'm not sure this will help but here goes: I switched from 5.13 to 4.56 when the PO's rear diff gear install blew up. I have the 4.0 with the 5 speed manual and 35" tires. I only get offroad occasionally but when I do it is to Moab, Grand Staircase, SW Colorado, etc. My routine driving is at 4800-5200 ft.
I chose the 4.56 because Yukon had a lifetime warranty in the Dana 44 pumpkin; the 4.88 did not. (I'm not recommending this thought process--just being transparent for my thinking at the time.)
I'm not unhappy with the 4.56 but I'm in 4th gear quite a bit on the freeway--especially when climbing. I don't feel very comfortable driving the TJ faster than 75 so the 4.56 top end potential isn't much of an asset.
I don't pull a trailer yet but given what you've described, I would lean to 4.88s.
I chose the 4.56 because Yukon had a lifetime warranty in the Dana 44 pumpkin; the 4.88 did not. (I'm not recommending this thought process--just being transparent for my thinking at the time.)
I'm not unhappy with the 4.56 but I'm in 4th gear quite a bit on the freeway--especially when climbing. I don't feel very comfortable driving the TJ faster than 75 so the 4.56 top end potential isn't much of an asset.
I don't pull a trailer yet but given what you've described, I would lean to 4.88s.
Tire size? Gear for the highway.
I would strongly lean 5.13, given that I preferred 4.88/33s/5 speed over that setup with 35s.
MARC CROMER
Member
I missed the important fact that I am moving up to 35" from 33", currently. I need to run in 4 gear on highway to keep up and 3 gear to make hills, with the stock gears on 33".
4.88 is the traditional recommendation. I have that. I wish the gears were deeper on the highway.
