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4.88 and 33" tires

Smittty9785

NAXJA Forum User
just a quick question. what would be the pros and cons of running 4.88 gears with 33" tires?
 
I've been running that combo for 4 years now with ZERO issues.
IMO it brings your power/torque curve back to normal.

John
 
I'm building a rig right now with 4.56s and 31" tires. Sounds like you're right on spec. to me.

Edit: If you are planning on a lot of rocks, lower is always better, but for an all around rig, 33's and 4.88s are right in.
 
Really! I was thinking 33's and 4.10's put it damn near stock. I do a lot of highway driving so that's what I was gonna do. 95', AX-15, NP231
 
I have 33's with 4.10
skip that and atleast run 4.56 and as above if you have the 4.88 that may be good too.
4.10 is ok for crusing, but even then the engine has to work little harder on uphills, downshift to pass. 4.56 atleast would be much better, but I set up for 31's first... than got hit with inchitis.
 
arctycfox: You're right, 4.10 are damn close to stock.
Hell, the Rubicons roll out with 4.10s and 32"s. The only downside I could see to the 4.88s(or my 4.56s) would happen at around 75-80 on the highway.
As in you would be traveling about 62MPH when the factory speedo was at 75mph. Probably need an adjustment there.

I still say 4.88s and 33"s sound about right. I didn't mean to imply it was a stock setup.


Edit 2000xjclassic:
http://www.naxja.org/forum/showthread.php?t=955626 Isn't this just one of Fords better ideas?
 
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alright, well whats it gonna be like with 31"s? should i wait till i get the 33"s before i do the 4.88s? the rig only see's the highway when im headed wheelin
 
I'm rolling 4.56 gears on 31's (worn down to 29's) and it isn't too bad. With the auto tranny I roll 2500 RPM at 70MPH. 4.88 will put you near 2675 RPM at 70MPH. I love 4.56 with 31's.
 
33's and 4.88's is great with a renix motor the HO we had did well with it as well but seemed to deep on long freeway runs with a manual trans but was SWEET in the rocks with a 4:1, like it was said before in rocks you can not be to low
 
well considering my goal is to make it up a certain trail that i have a vengence for, 4.88s sounds like a good set-up then!

Question is.. will the stock D30 front with 4.88's handle 33''s ok? i was thinkin about getting an aussie for the front
 
NW-XJ-Scott: with the 4.88s and 31"s it,s about 57mph at a registered 75mph

As long as you're not in a hurry to get to the dirt, go ahead and do the gearing before the tires.

By the way; for all the math I was using:
225-75 or 235-75 15s(about 28.5-29") and 3.55 stock gearing
 
based on the calculations that I have done for the AW4 tranny
27 inch stock tire and 3.55

27/3.55 = 7.60 so this is about the tire to gear ratio that you want so that it is feels near stock. Each of the number below will ballpark back to roughly stock value. I am now running 31 and 3.55 for a ratio of 8.73 and it really blows.

One point of physics not taken into acount is the inertia of the bigger tires. They hold more energy as they spin up to highway speed so to apply that energy you should aim for a lower than stock ratio not higher than stock.

So, for the 33 inch tire and lots of highway mileage 4.56 gears would be about right. For 33 inch tire and less highway miles the 4.88 is where I am shooting for. I am currently on the high side of the stock ratio and it sucks. I would prefer to be on the underside of it.


27/3.55 = 7.60 this is where my jeep started.
29/3.73 = 7.77 why bother re-gearing for 29 inch tires?
31/4.10 = 7.56 very close to stock
33/4.56 = 7.23 this is good if you drive lots of freeway miles with no mountains
35/4.88 = 7.17 this is good if you drive lots of freeway miles with no mountains


Again 7.60 is the ratio that I wanted to stay under because I have not boosted HP with engine mods for that stock like feel in throttle response.

How far under depends on what you do with your jeep.

I have spent a few years with 31/3.55 and it blows... Did I mention that?
I plan on a final tire size for this xj at about 33-35 inches so I will be going with 4.88 gears. I do some Mud, some Sand, and Rocks when I can find them but Michigan is not a Rock Crawling Meca. I drive to the dirt so I can not going crazy like 5.89 or anything like that. Jeep gets about 1500 miles per year so I can live with it being slower on the freeway.


Happy Trails
Jeff
 
GI-John said:
I've been running that combo for 4 years now with ZERO issues.
IMO it brings your power/torque curve back to normal.

John
Especially considering the greater tire mass. I have been running the 4:88/33 combo for a couple of years and love it off road. I've often wondered that my highway mileage might be better on 35s, though.
 
As you can see There are many many opinions on this subject.
Here is my take on the subject

If you have to drive a distance to play or use the Jeep as a daily driver.
31s-32s= 4.10, 32s-33s= 4.56,
You can get away with 4.10s & 33s if you truly live in a nice flat spot or drive mostly on road, Hey there are guys running 33s with stock 3.55s !

If you use your jeep as an off road toy only or as a tow vehicle.
31s-32s= 4.56, 32s-33s=4.88

Remember this is Just my opinion, Your own opinion my be different!!
In my AW4 equipped XJ I run 31s - 4.10s & am very happy, It even gets good (Average 18MPG) Milage for a Jeep & Most of my off roading is on the beach!.
 
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what would you recomend for a 99 5spd xj DD im going 4.10s 33's will that be bad?? im doing 4.10s because i can do it for 450.00 total....
 
I DD mine(check Sig), and I have no issues. Gase milage is great @ 60mph. Only hurts if you try to go above that. Off road the low gears are nice to have. I can also idle up hills in 2hi in first gear now :spin1:
 
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