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Discussion Starter · #1 ·
My '99 TJ is currently running 315/70-17 tires with a Dana 30 front and Dana 35 rear with 3.07 gears. I'm wanting to upgrade to 4.56 gears. What is the best way to do this.........buy new stuff or find used gears? I'll have to re-gear both the front and rear correct?

If I buy new stuff what all do I need to get to do a complete gear upgrade?

Never dealt with gears before so I'm pretty clueless on this subject. I picked the 4.56 because that's what is recommended on the gear charts I've seen for the 34 to 35 inch tires.
 

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Best way is take it to a differential shop, and let them supply the parts. That way, you get a full warranty. Regearing isn't something you would want to try yourself if you have never done it before.
 

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Best way is take it to a differential shop, and let them supply the parts. That way, you get a full warranty. Regearing isn't something you would want to try yourself if you have never done it before.
X2 and always buy all new components.
 

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First, that is roughly a 35" size tire. A 4.88 ratio would be appropriate if your transmission is the 5-speed & your engine size is the 4.0L.

BUT... that big of a tire is too big for your rear Dana 35 where 33" is the commonly accepted biggest size you can safely run. The axle shafts inside your Dana 35 simply aren't strong enough for that big of a tire & you can count on a broken axle shaft sooner or later.

The only way to somewhat safely run that big of a tire would be to also install hardened alloy axle shafts into your Dana 35 like from G2 axles.

And never install used gears into an axle unless you are prepared to pay the shop extra labor since it takes much longer to set up used gears. They must be shimmed with much greater care so they mesh precisely the same as they did in the old axle they came out of. Unless you are installing the used gears yourself, and it takes an expert to do so, it is usually never worth the slight/very minor cost savings over simply installing new gears.
 

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FWIW it's worth you might want to consider upgrading the D35 at least. When I was calling around for quotes on regearing in my area I was quoted ~1000 an axle by 5 different shops (This includes gears, labor, all the misc install parts). At that point I decided to just buy an 8.8 with the gears already set up. Looked for a D44 but couldn't find one in my price range.

You will need both front and back if you plan to use your 4 wheel drive.
I agree with the others and you should get the gears and set up kit from the shop doing the swap.
You'll need to swap a speedo gear to get your speedometer accurate.
 

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Discussion Starter · #6 ·
First, that is roughly a 35" size tire. A 4.88 ratio would be appropriate if your transmission is the 5-speed & your engine size is the 4.0L.
Transmission is the 3 speed auto and yes, it's the 4.0
 

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With the 3-speed automatic and 4.0L engine, you want 4.56 for 35" tires... which are too big for a stock Dana 35 rear axle. :)
 

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Discussion Starter · #8 ·
Even if I switch to 33's, 4.56 fears would be good, right?
 

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Discussion Starter · #11 ·
Jerry, you mentioned swapping axles, where can direct swap in axles be found?

Like I said I'm clueless about gears and axles. My jeep was set up the way it is when I bought it. My goal is to get it to it's best performance with the eng. and trans. that I have.
 

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Finding direct bolt-in replacement axles for a TJ is not easy, you just have to frequent the For Sale classified in the various Jeep forums, Craigslist, local Jeep clubs, etc.. It can sometimes take a while to find what you're looking for.

You could drop down a tire size to 33" and keep your Dana 35 stock until you can beef it up or replace it.
 

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Discussion Starter · #13 ·
Thanks Jerry, that's most likely what I'll do. Do you think the 4.56's will be a good choice? (I may go to a larger tire in the future)
 

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4.56 would only be the ideal choice for 35" tires Rewind, 4.10 would be the ideal choice for 33" tires.

For others reading this, those axle recommendations are only appropriate for the 3-speed automatic and 4.0L engine. They would not be appropriate for any of the other possible Wrangler transmissions.
 

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4.56 would only be the ideal choice for 35" tires Rewind, 4.10 would be the ideal choice for 33" tires.

For others reading this, those axle recommendations are only appropriate for the 3-speed automatic and 4.0L engine. They would not be appropriate for any of the other possible Wrangler transmissions.
I thought that 4.10s, 33s, and the 3 speed auto would be similar to my 4.56s, 33s, and 5 speed. I couldn't believe how much higher it revved compared to mine. Ryan aka GoldenSahara00 said that at 70mph he was at 3100 rpm after he did his Ford 8.8 swap. I'm at 2800rpm at that speed which is reasonable. Not really arguing one way or another, just a commentary on that set up.
 

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I thought that 4.10s, 33s, and the 3 speed auto would be similar to my 4.56s, 33s, and 5 speed. I couldn't believe how much higher it revved compared to mine. Ryan aka GoldenSahara00 said that at 70mph he was at 3100 rpm after he did his Ford 8.8 swap. I'm at 2800rpm at that speed which is reasonable. Not really arguing one way or another, just a commentary on that set up.
That 3-speed automatic/4.10/33" tire size combination only generates 2750 RPMs at 66 mph, about right for a 3-speed automatic without an Overdrive.

Use this calculator to figure out the engine rpms for any transmission/axle ratio/tire size http://www.TommyJeep.com :)
 
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