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Replacing 3.55 with 4.56 - Dana 30 Chrysler 8.25

Mudderoy

Mudderoy

NAXJA Forum User
Location
Katy, Texas
I am sure this question has been asked before and I spent the required 32.3 seconds searching before posting. ;)

Beat me up for not searching long enough if you will, but then answer the question. :twak:

I recently sold my old factory Jeeps wheels and tires so I have MONEY to spend on Jeep parts. I have read that re-gearing will help get the MPG back closer to factory.
Irregardless I knew that when I went to larger tires I was going to have the change the diff gears eventually, the gas usage just moved it up the "to do" list.

1. What brand of ring and pinion should I consider?
2. I found a package deal on completeoffroad.com for 4.56's and installation kit for $449 (http://completeoffroad.com/i-124189...0-chrysler-8-25-gear-install-kit-package.html) Good, bad, or ugly?

I am going to have them professionally installed :( as per several recommendations.

Anything else you can think of to do, or watch out for?

Oh, and I would like to install the locker in the 8.25 right now, but I cannot afford it. The one I am getting is a "lunchbox" locker so I should be able to do it myself anyway.

:helpme:
 
Maybe it's just me, but I didn't see a brand name in that ad anywhere, so that would make me leary of them. Always know what you're paying your hard earned money for, and buy a good brand like Dana/Spicer, Richmond, Precision, Yukon, etc. and you'll be fine.

Also, you'll never get your mileage back to stock. You will definately improve it with proper gearing, though. You have to remember that now you're pushing around a lot more weight in the form of heavier wheels and tires, plus all of the extra junk most wheelers carry around with them that a normal soccer mom wouldn't in that same stock XJ.

What size tires are you running?
 
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I am running Yukon's in mine and from what ive heard, they are the best. if you want to do a locker, do it at the same time because if you have your gears profesionally installed (waste of money imo) then chances are you will void the shops warentee on the install and it just easyer to do everything all at once. if the shop wont warentee the install i wouldnt let them touch your jeep. hope this helps.
 
Georgia Mike said:
Maybe it's just me, but I didn't see a brand name in that ad anywhere, so that would make me leary of them. Always know what you're paying your hard earned money for, and buy a good brand like Dana/Spicer, Richmond, Precision, Yukon, etc. and you'll be fine.

Also, you'll never get your mileage back to stock. You will definitely improve it with proper gearing, though. You have to remember that now you're pushing around a lot more weight in the form of heavier wheels and tires, plus all of the extra junk most wheelers carry around with them that a normal soccer mom wouldn't in that same stock XJ.

What size tires are you running?
Click to expand...

Yea I didn't either. I think they are Yukon. I'll find out before I buy. I was afraid I'd call and they'd say a brand I didn't know. Hence the questions here. I would think Dana and Spicer would be good but sometimes that assumption isn't true of all things they sell.

lol, well I'm at 11 mpg now, so I'd kill for the 15-17 that other people are getting since they re-geared.

32x11.5x15
 
jpcherokeekid said:
I am running Yukon's in mine and from what ive heard, they are the best. if you want to do a locker, do it at the same time because if you have your gears profesionally installed (waste of money imo) then chances are you will void the shops warentee on the install and it just easyer to do everything all at once. if the shop wont warentee the install i wouldnt let them touch your jeep. hope this helps.
Click to expand...

Thanks good advice. My mechanic is a friend of the family. His mom and my mother-in-law are best friends. So it won't be a problem, otherwise I'll tell my mother-in-law, etc... :D

What did you guys have to buy besides the ring and pinion? Another carrier? Crush sleeve? I understand about the RTV and fluid that will have to be replaced, but anything else needed?
 
muckleroy said:
Thanks good advice. My mechanic is a friend of the family. His mom and my mother-in-law are best friends. So it won't be a problem, otherwise I'll tell my mother-in-law, etc... :D

What did you guys have to buy besides the ring and pinion? Another carrier? Crush sleeve? I understand about the RTV and fluid that will have to be replaced, but anything else needed?
Click to expand...

You will need a new carrier for the Dana 30 as the carrier break is at 3.55. You will need a carrier for gears that are 3.73 and numerically higher. I would purchase the fluids my self. I tell you this because I learned the hard way that the dealer's gear lube costs about 4-5 dollars a quart. I could have saved about 10 bucks buying my own lube, plus you will be replacing it in 500 miles after break in.
 
The master install kit will include new bearings and seals too. This is the bulk of the cost of the master install kit. I would recommend it if you jeep is like most with over 100k miles on it.
 
muckleroy said:
Yea I didn't either. I think they are Yukon. I'll find out before I buy. I was afraid I'd call and they'd say a brand I didn't know. Hence the questions here. I would think Dana and Spicer would be good but sometimes that assumption isn't true of all things they sell.

lol, well I'm at 11 mpg now, so I'd kill for the 15-17 that other people are getting since they re-geared.

32x11.5x15
Click to expand...
Dana/Spicer would be good for the front, but you won't find a Spicer gear set for a ChryCo 8.25. I've got a Precision gear set in my 8.25, no issues.
 
Dana/Spicer > Precision/Superior > Motive > Yukon (premium or not) > Genuine

IMO. I wouldn't run less that precision/superior.
 
On another note be careful when you air down you're tires, you can blow beads like crazy on such a wide rim.
 
All great information, thanks guys.

Can anyone recommend a good online store for a source for these parts. I'm looking around trying to find one, but it's slow going.
 
I'm running 32X11.5's and getting 15 mpg solid. Don't forget to add 10 % to your recorded mileage when figuring MPG if you are running the stock speedo gear and no other correction for the big tires. I also run my truck in 3 rather that OD. Actually gets better mileage and keeps the rpm at highway speeds nearer where it should be without lugging.
 
I've got a Dana 30 carrier that you can use for the 4.56 gears. It's complete with spider & drive gears, cross shaft, and bearings (no races).

$30 + shipping and it's yours.
 
rmm727 said:
You will need a new carrier for the Dana 30 as the carrier break is at 3.55. You will need a carrier for gears that are 3.73 and numerically higher. I would purchase the fluids my self. I tell you this because I learned the hard way that the dealer's gear lube costs about 4-5 dollars a quart. I could have saved about 10 bucks buying my own lube, plus you will be replacing it in 500 miles after break in.
Click to expand...

Are you sure the brake is 3.55? Because my buddy has one that came stock with 4.10's, you sure it's not 4.56's?
 
hot_rod_hooligans said:
Are you sure the brake is 3.55? Because my buddy has one that came stock with 4.10's, you sure it's not 4.56's?
Click to expand...

IIRC the break is at 3.73
 
So anyway going from 355 to 456 will increase your rpm like 28%

(456-355)/355

Driving in 3rd gear 1.0 ratio compared to 4th .75 ratio will do nearly the same thing. I know it'd be nice to have the gears, but here's my point.

Drive around a tank or 2 in 3rd gear. If this doesn't increase your mileage the gears won't either. Just something to think about before regearing.

Some will argue that the ratios in first and second when accelerating are a factor as well. That may be true, but for highway mileage it's apples and apples.
 
What you're not realizing with that scenario is that a vehicle uses more fuel to get going from a stop than it does while maintaining highway speeds, especially if it's overgeared for the tire size (IE: 33's on 3.55's). That's one of the main reasons the "city" mileage rating is always so much lower than "highway" mileage ratings.

If he's going to be doing almost all highway driving with very little stop and go driving, you have a valid suggestion to for an MPG experiment. If he runs into stop & go traffic, the experiment's results be get more and more skewed every time he stops and has to get going again.

Plus I don't have to mention that driving with an overgeared axle/tire combination is very hard on an automatic transmission because of excess heat. Also, it's hard on a manual transmission's clutch due to excess slipping needed to get the vehicle rolling.

Gears are worth the effort. Period.

:peace:
 
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ratcat said:
Drive around a tank or 2 in 3rd gear. If this doesn't increase your mileage the gears won't either. Just something to think about before regearing.
Click to expand...
You are right, but you are also wrong.

One thing you lose sight of is starting from a light or dead stop in first gear. You have to waste a lot more energy getting started. Also there is a much bigger jump from 2nd to 3rd then there is from 3rd to 4th. If you are driving around in third all the time and have to downshift, your RPMs will make a much bigger change requiring much more fuel.

BTW...after having several jeeps with several different gear sets in all of them. Changing the ratio to 4:56 will net you much much better fuel mileage. As long as you don't expect it to be stock.
 
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