After driving around for 3 years with 35's and 3.21's I finally regeared my Jeep to 4.88. It says that the break in time is 500 miles for the rear, but my question is: Is there a longer break in period for the front since it is under almost no stress while not in 4WD? I don't really want to waste the fluid and not get a proper break in by changing it at 500mi with the rear if it takes longer to break them in. This is my first time regearing myself so I'm kinda nerves to see what happens for 500mi. But I've got 75mi down and 425 to go and no problems yet!

 

I'm also curious, I will be doing re-gearing soon too.

Dezertjeepin,

How do you like the change? Any change in MPG's?

 

I had mine done by Clayton offroad and they recommended around 1000miles for breakin, 500 in grandma mode. Just swapped my oil last night along with new covers and all looks good, no real signs of any problems. With a good synthetic in there it seems to be driving much better (coasting and mpg).

One thing, I'm happy I took the covers off, since some of the fluid did not drain from the front with just the plug, and I wanted to get ALL the break on fluid out.

 

How do you like the 4.88's?? Real big difference? I've been struggling with the 35's on 3.21's and about to lose my mind.

 

THe gears turn the whole time even though they arent under power. That should work out the shavings, and provide some heat. It seems that your front gears should be nearly as "broke in" as your rear gears. I am not an expert though....

 

Thanks guys. I actually did the regear myself. And with a lot of research and fingers crossed very tightly, Hopefully they work out. I'm big on DIY stuff and am pretty good with thinking things through. I personally like a challenge (and like to save money) but have been kinda nerves to do it. I've only put a little less than 100 miles on it so far but have been babying it the whole time. So far so good! I haven't heard any noise come out of the rear yet.

Planman: Never read/heard anything about an "initial heating and cooling step." All it says in the install book is to "drive vehicle lightly for 15-20 miles and stop and let the rear diff cool" Is this what you're referring to?

As for how much I like it...... Its WAY different!!! Like I said, I'm still breaking them in so I haven't really had a chance to get on it yet, but the power off the line is great. I think the 4.88's will work out well for me because I live in the mountains and only hit the freeway a few times a month. The fastest I've gone so far is around 60MPH and spinning the motor at 2600+ so I'm not sure if I would like it much for daily driving on the freeway. I do have pretty bald 35's right now so they are only measuring out to about 33"ish so with new tires it might be a little better. Ill keep you guys updated soon when the gears are broken in and I take it out wheelin.

 

Drove mine like I stole it. 80mph down the interstate. Gears still going strong 50,000m later.

 

This will probably be me when I get my gears done. I won't drive back 30MPH from Northridge4x4. That will take me like 3 days when it is a 5 hour trip.

 

Same... But I'm on the East side of the state. I'll be hauling ass all the way home!

 

So I've got about 350 miles on the new gears now. The gears themselves are doing great and I haven't had a single noise/problem. But the locker on the other hand...

It definitely handles differently with a locker in the back, but I expected that. But this is not what I expected... If I have my foot SLIGHTLY on the throttle (almost in a neutral position. Not accelerating, nor decelerating) when I go around corners it surges/lunges back and forth. Similar to the feeling of being in a car with a newly licensed teenage driver learning how to drive a stick. I have the Spartan Locker (lunchbox style similar to Ausie/Powertrax/Loc Right) and expected a little clanking and noise from it releasing but not like this! Some corners it's fine, some it's not. Like I said, it's mostly when I'm barely touching the gas.

The second thing I think is odd... When I shift gears for the first few gears there is a quick grind like the syncros arent doing their job. If I go slow it doesn't do it, or at least it's very faint. Anyone had this issue after changing gears? I've got 60,000 the motor/trans. But I NEVER had this problem before the new gears.

Other than that everything is good and I'm super stoked about my how my first gear install went! I've got a set of 37's I'm going to put on to see if they would be a good fit so after I drive it around with those I'll let you know how I like te 4.88/37's combo over the 4.88/35's combo.