Does any one know which axles are in the crd's? Also what gear ratio's are availble, I'm thinking of re-gearing for milage (have 3.73 gears now).

I've had the same idea...changing the gears out with the goal of gaining fuel economy. It would seem that we could increase our highway mileage on the freeways by gearing a little taller and running the engine at lower RPM. I've wondered what is available too. I think Libby's with the six-speed came with something like 3.55's probably to make up for it's lower overall ratio. I think that would would reduce engine speed by about 200 rpms. For those of us with the '06's we wouldn't want the limited slip varieties because of the ESP.

I can't help but comment on this.

Changing diff ratios for highway mileage on a 4wd?? What on earth has possessed you guys to consider that as an option?!

Buy a TDI if you want fuel economy improvements on the highway - you'll be surprised in a positive way when you make the change. On the other hand you will most likely be disappointed if you change diffs and don't gain a single MPG because the main factor at highway speeds is the air resistance, not the drivetrain resistance.

Try a better diff oil if you want to fuss about with diffs, I really don't think it will help you enough for the price two new diffs for it to be worth it!

No, KJs only came with 3.73s and 4.10s. There are many gear options including 3.55s for the 8.25 rear. There are no ring and pinion sets for the front end as the D30A uses a different length pinion gear.

I am looking at this from the same angle as you are.......going 3.55s for highway cruising. the 3.55s for the rear aren't a problem, its the front that is the problem.

Actually they make 3.21 gears(standard on '08 KK's) and 3.55 gears(only on 6 speed KJ's) for the D30A as inaddition to 3.73's and 4.10's.

By adding higher gears with the same tires is basically the exact same as adding larger tires with the stock gears,you will loose MPG's in a KJ and have that feeling of power lose.Also you will be adding extra stress on the tranny and t-case.

Uffe - Austin to Colorado - 900 miles, Austin to Moab 1200 miles (one way) - highway gears are reasonable as long as I don't tow.

Sir Sam - most of the diesels around here are trucks and they come with 4.10/4.11's - for towing - in fact It's assumed if you have a diesel you're using it to tow.

Although I'd bet CRD's have 3.73's because most Liberties have 3.73's and adding another gearset to the distribution channel was too expensive for Chrysler.

With tires - weight is also a factor especially in town - when I went from stock to MTR's I lost 2-3 mpg - but I think they're a lot heavier than Darby's Hercules.

At 55mph I get 20mpg, if I speed up to 62mph to get the second overdrive and slow down to 57mph I gain 4mpg. This is why I think a gear change would be worthwhile. To take advantage of the low end torque, since the f-37 recall screwed with the shift points.

Going to a higher gear set will screw up your shift points even more,your TCM will only learn so far within a specified range,going to a higher gear set will be out of that range and the best torque range of your engine for cruising at higway speeds.

The CRD doesn't make that much more torque then the 3.7,about 70-75lbs -ft or torque,yes it is made at a lower RPM but the CRD will be effected,though not as much,as a gas KJ would by adding a higher gearset and keeping the same size tires.Spending a $1000 for a slight loss of MPG's and no other benifit doesn't make much sense but by all means do it,then I get to laugh when your start complaining that you spent all that money and lost mpg's.

Your driving a 4300lbs brick that is 4wd,be happy with 20-25mpg's since no other vehicle in the KJ's class with the same capibilities does not get that kind of mpg's.

You can nearly get an old TDI for the same money as you will have to shell out for those gears + labor costs (your own time at least).

1200 miles on highway with a 4wd??? Is that an argument at all?? Minimum 44MPG on the TDI vs maximum 33MPG on the KJ, if you do that much highway driving, why don't you consider that change?

The gears are for economy right? Why not spend your money more wisely and do the math: Gears may give you 2-3MPG boost while the TDI will give you at least 11MPG boost (worst case TDI vs best case KJ).