locking hubs and gas mileage

I searched a little and I think I get some of the idea, but I was wondering from people who know and have done the swap. On my 89 XJ, I am thinking of getting manual hubs in part to help with gas mileage. I live in Hawaii and I need to drive long distances to get anywhere. I have a couple questions:

1: what kind of mileage improvements can I expect?

2. how come I can't find these for sale on jcwhitney, ebay, etc?

3. are all front axles on MJ's dana 30's? I have D44's on the back

4. no way in hell am I spending several hundred dollars on some, how do I get them cheaper?

Thanks guys.

You should already have the disconnect front axle. It may help some but would be better improvement for the non-disco axle.

I think you can expect a 0 mpg improvement. There isn't as much drag as you think.

When I was re gearing my front axle, I drove with no front shafts for a couple of weeks. I got maybe 1/2 a mile per gallon better mileage. It wasn't enough to change the mileage noticeably.

And the only way to do it is to spend several hundred bucks. Unless yours is heavily modified, and you're having other issues, it's not worth it. You would never save enough in gas to pay for it.

And yes, you have a D30 front axle. You don't see the hub conversions most places because it's not really very popular.

Hope this helps.

Todd XJ said:

I think you can expect a 0 mpg improvement. There isn't as much drag as you think.

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sweet, I've got an extra $1000 weighing down my pocket, think I'll get a pair.

just kidding thanks for the wakeup call

purvisdotcom said:

sweet, I've got an extra $1000 weighing down my pocket, think I'll get a pair.

just kidding thanks for the wakeup call

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Spend it on skid plates/protection and good quality recovery points, you will thank yourself many times over.