[derf]

With 5.13 and 37s, I can truly crawl the 4:1 transfercase. I built my rig to crawl - street performance was only secondary. 5.38 would have been amazing offroad but just too low on street IMHO. It is all about balance. I am an automatic.

2700+rpm is not a bad thing in the 3.6 like it may have been in older engines. I am not sure how true it is but read somewhere Pentastar 3.6 hits its optimum power band somewhere around 2800-3000rpm.

It's lower than that. Mid to low 2,000s, maybe 2,100 to 2,600 is where it's happiest on the freeway.

 

[shep546]

So I really want to go with 4.88s but even with the cryo treatment I'm worried it's too much to stuff into a dana 30... really don't wanna blow up my $1200 locker

 

[khickeyman]

You will be fine I thought the same thing. I had the fellas at Northridge 4x4 do my install. I was going to go with 4:56's but when the guys saw how much gear I had on, plus me living in Wyoming with all the hills and pulling a trailer some of the time they said they would rather have me do 4:88's As for happy around 2000-2600 rpm for me I would have to disagree at least on mine. Mine liked to fall on its nose at 2200 before gear install and stock 32's I never saw 6th gear unless I was on flat ground going to Colorado and in 5th I was constantly around 2800-2950 on interstate. trying to maintain 75mph .Now with new gears I'm at 2850 in 6th with 315's and 4:88's and pull hills with out having to gear down to climb hills around here

 

[mommymallcrawler]

So I really want to go with 4.88s but even with the cryo treatment I'm worried it's too much to stuff into a dana 30... really don't wanna blow up my $1200 locker

Only lock the rear D44, problem solved.

 

[marslim]

You will be fine I thought the same thing. I had the fellas at Northridge 4x4 do my install. I was going to go with 4:56's but when the guys saw how much gear I had on, plus me living in Wyoming with all the hills and pulling a trailer some of the time they said they would rather have me do 4:88's As for happy around 2000-2600 rpm for me I would have to disagree at least on mine. Mine liked to fall on its nose at 2200 before gear install and stock 32's I never saw 6th gear unless I was on flat ground going to Colorado and in 5th I was constantly around 2800-2950 on interstate. trying to maintain 75mph .Now with new gears I'm at 2850 in 6th with 315's and 4:88's and pull hills with out having to gear down to climb hills around here

I agree. Numbers only tell part of the story, my 2012 with 3.73 and 33's was pretty gutless in the hills, I would be down into 4th gear over 3000rpm to try and maintain 70 mph o the highway. Now with 5.13's and 35's I can pull the same hills at 70 in 6th gear at 2800 rpm.
The dyno charts are helpful but don't tell the whole story

 

[derf]

So I really want to go with 4.88s but even with the cryo treatment I'm worried it's too much to stuff into a dana 30... really don't wanna blow up my $1200 locker

If you keep the locker turned off until you desperately need it, you can really extend its life. Leaving the differential open and allowing the tires to slip does wonders to reduce stress on everything in the front axle.

If you're really hung up on it, you can take all of the money you were going to put into the D30 and get one of the aftermarket D44's that are out there (Dynatrac, Currie, G2, and maybe others). They are all considerably stronger than a Rubicon D44 (which is really just a D30 with a D44 R&P/locker) and don't need any kind of truss/gusset additions. Swap a few parts over from your D30 and it bolts right in. It costs a little more than throwing parts at a D30 but it's a lot stronger.

 

[MrKyle513]

4.88 is what I think they recommend with 35's and manual trans in the 3.6 for optimum split on and off road performance. I have 4.56 in an auto and 35's. Its my daily driver and I drive about 20K miles a year in it so I wanted a little lower RPM on the highway. The installer did try to talk me into 4.88's, but coming from 3.21's, the gears I got feel like night and day. I'm happy with it.

Hi, my 98 TJ has the D30 front. Would i have to invest in a larger carrier for the 4.56 or 4.88? Or- will the factory D30 carrier hold this?

 

[Old Dogger]

Hi, my 98 TJ has the D30 front. Would i have to invest in a larger carrier for the 4.56 or 4.88? Or- will the factory D30 carrier hold this?

Welcome to the Forum, from Cave Creek AZ.

 

[GuzziMoto]

Hi, my 98 TJ has the D30 front. Would i have to invest in a larger carrier for the 4.56 or 4.88? Or- will the factory D30 carrier hold this?

As I understand it, it depends on what gearing it started with. If it originally had 3.21 gears it will need a new carrier. If it originally had 3.73 gears it should be fine going to 4.56 or 4.88 gears.

 

[Bobnh]

Hi, my 98 TJ has the D30 front. Would i have to invest in a larger carrier for the 4.56 or 4.88? Or- will the factory D30 carrier hold this?

Yes, you can fit 4.56 or 4.88 gears into a TJ d30. As was stated, having to change the carrier depends on current gearing. You almost certainly have 3.07 or less likely 3.73, unless you have a 4cyl which could potentially have 4.10. If yoy have to go bigger anyway, think locker or trutrac, which I had in my TJ d30 with 4.88 gears.
But you will want to ask to have this request moved to the TJ forum.
And welcome to the forum.

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