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4.56 to 4.88 potential overgearing?

O

Outlander560

NAXJA Forum User
Location
New York
Hey guys I have an 01 xj aw4 np231....my front d30 needs to be pulled out do to some issues (seals, pinion preload was not set properly, LCA mount broke) and I was recently offered from somebody to purchase my axles I have is a d30/c 8.25 front is open and rear is detroit locked...4.56s I'm running a 5.5 inch lift with 33 kevlars.

My questions are:

1.)Should i sell these axles and buy the d30/d44 combo. rear is locked both with 4.88s disc brakes/ chromo shafts..front disco 30 (i'd get rid of the disco and put a full shaft in its place)

2.) Going with the 4.88s will I potentially over gear running 33s? will it be to much?

3.) Or should I just re gear one of the d30s sitting in my basement and keep the 4.56s?
 
do you do a lot of highway driving? or mostly wheeling? 4.56's will probably be a little better with the 33's on the highway. i ran that for a short period and i had no desire to go with 4.88's for daily driving. now i run 35's on 4.56's and it could stand to be a little lower offroad, but it's decent on pavement.
i'd probably go with an atlas or 4:1 transfer case before i regeared again.
 
it is my main vehicle...i do a lot of highway driving and a good amount of offroading...low speed crawling not really a huge fan of mud pits anymore
 
really well that is interesting learn something new today...so sell my 4.56s and get the 4.88s i have 1 vote...still on the edge tho by the way the kevlars are 33x12.5x15
 
4.88's will be overkill on 33's, but not impossible to deal with.

The real question is, do you plan to go bigger. If everything works the way you want it now and you have no desire to go bigger than just fix your D30. If you want to potentially trade up to 35's then make the deal.
 
Assuming an auto:

4.56 and 33's, 65 mph is 2263 RPM's
4.88 and 33's, 65 mph is 2422 RPM's.

The difference is so small it just does not matter. ...But getting up to speed the increase in power and torque will make the care more driveable, and increase economy as you'll use less throttle.
 
eventually go to 35s...but these tires still have a lotta meat on them...thinking about the opinions you guys are making...maybe i will just fix my d30 like Dutch said..then when the time to go to 35s comes get rid of the 30 and go for a bigger axle maybe a d44 front
 
so Cal if I understand correctly your stating although I will be running at a higher RPM with the 4.88s the benefits of increased torque/power and increase in economy will lean me more towards 4.88s
 
If you are 100% highway driving, you may not gain economy - but if you do a lot of around town driving, driving in hills, etc. then you can gain economy from deeper gearing.

Either way, if you lose economy, we're talking fractions and not miles per gallon lost. A difference of two hundred RPM's at speed is not going to make or break anything..

If you think you're going to 35's later, def go with the 4.88's.
 
cal said:
and increase economy as you'll use less throttle.
Click to expand...

Don't start this again hasta That's debatable at best, if not outright false.

OP: As someone else mentioned, the difference between 4.56 and 4.88 is very small. However, that being said, 4.56 is already over-geared for 33's. So there's really not much reason to go to 4.88. You're really gunna be pushing the limits of the 30's r&p with 4.88's as well.
 
Milford Cubicle II said:
Don't start this again hasta That's debatable at best, if not outright false.
Click to expand...

False, except that is the experience of many naxja members...

Milford Cubicle II said:
OP: As someone else mentioned, the difference between 4.56 and 4.88 is very small. However, that being said, 4.56 is already over-geared for 33's. So there's really not much reason to go to 4.88. You're really gunna be pushing the limits of the 30's r&p with 4.88's as well.
Click to expand...

You mean as I mentioned? Right before you said its false? ;)

Also, no evidence to say that 4.88's is pushing the limits of the d30. As many 4.56 gearsets break as as 4.88 gearsets do..

And he did say he intends to go to 35's later.
 
i experienced worse gas mileage after gearing, but i do have a heavy foot, so take that for what it's worth. with a manual trans, i did not like the lower gearing, i prefer the 4.56's on 35's more than on 33's. I shift less around town. highway driving is about the same, i still have to downshift on certain hills, just like before. however, i feel that i can go 80 more comfortably with the 35's as it isnt screaming as much. if you drive 65, then the lower gearing won't matter as much.
the ho 4.0 has a ton of torque and i never had a problem getting off the line quickly, even with the 3.07's. I actually prefered higher gearing around town.
you did not mention you were going to 35's earlier, so i would probably consider 4.88's more seriously then. but i am not disapointed with the 35's on 4.56's either.
 
Cal: I'm not 100% highway driving I do a lot of off highway use with my jeep and will continue to do so probably more....but i also use it to commute back and forth 2 work 45 miles one way...

Gas mileage it is what it is..i changed the vehicle and upgraded it so I'm not looking for a hybrid some + in economy would be sweet tho...

But I would like to get a little more nut. when I drive to college (250 mi) the hills out in the CNY country roads make this puppy pretty sluggish on hills most of the time up shifting is needed to keep up with the 60-70 mph (AW4)

To go with what was said by Milford I understand and have done a lot of reading about it and know the carrier becomes the weak point especially with my chromo shafts and gears..and if not that then the case itself...so I have also decided I will be going with an ox locker (no arb, or power lockers) i have been thinking about a truss although to but thats not the topic of discussion currently.

I see that 4.56 to 4.88 is minimal and if the benefit is not huge I will keep for d30 and c8.25 for now...the other things that attracted me towards the d30/d44 was that the d44 had chromo shafts and disc brakes as well
 
Vanimal: the 35's will come in time...but the kevlars have a lot of meat on them still so the upgrade from 33s to 35s won't happen anytime soon
 
The 8.25/44 discussion can go on forever, there are a ton of arguements either way. The 8.25 has a stronger housing and stronger pinion gear, the 44 has chromo shafts available, and is not c-clip so when you DO break a shaft, its easier to limp your way to a tow truck. The 44 housing is higher clearance and has more general aftermarket support - as well as you find more people running 44's than 8.25's in most big group runs, so if you absolutely have to borrow spares they are easier to find.
 
yea haha i know the discussion of axle types is a big here and there, this and that dicussion and I don't want to get into that as I have done the research for that as well..the main topic for here is 4.56 or 4.88 and i do commute with it a lot...i guess you can list my jeep as a weekend wheeler...but gathering your inputs I guess I will keep the 4.56 for now slap the new rebuilt one in....while I got you guys here on my thread any of you truss your axle? Did you build a jig to hold the axle in place pre welding so it did not warp? not looking for a huge topic to start just curious about it...from the research i did the prepping for trussing the d30 or any axle either has "i got lucky" or had some crazy bottle jack with chains holding the axle in place deal going on
 
Last edited:
From my personal experience, the first time I went to 35's, I was running 4.56 gears and an 8.25. I found it worth the cost to upgrade to a rear 44 and re-gear both ends to 4.88, just for driveability (this is before you could get 4.88's for the 8.25, which are now available).

Recently I bought another XJ from a friend who decided to get out of it.. with 4.56's and 35's. I've driven it about 200 miles total since buying it (~3 months ago)..

...and I now have 4.88 gears and install kits sitting on the garage floor waiting to go in it.

My personal thoughts and experiance. Your mileage may vary.
 
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