Considereing Swapping to 3.73 rear, but ...

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JPT

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Heh... I never said it didn't have to be set it up. What I quoted said it was not possible to swap internals...

Please re-read this part "I'm saying you can't buy the internals and just bolt them up".

It is not a simple bolt up like the OP was asking about.
 
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ilarson007

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It is perfectly possible to buy an entire axle assembly. You can buy them prebuilt, or used. I'm saying you can't buy the internals and just bolt them up. Search for the axle you want already with the correct gear ratio you want. Generally you will have to remove the brakes off of your axle, the drive shaft, vent tube, shocks, shocks, and swap in the new/used axle assembly.

What you have to be sure about is the bracketry. Make sure the brackets will bolt up to your truck. Otherwise you will have to do a lot of work.

Typically wanted axle assemblies (with wanted ratios) are expensive.

I understand now, but I didn't at first because of the Subaru setup. You can literally unbolt the Subaru rear end from your driveshaft, remove the axles, drop the diff, and bolt in your new one. Nobody regears them because they just purchase the radio they want. And most of the upgrades are to one specific differential that is much stronger than the stock WRX or. I've again, I've been spoiled by Subaru engineers.
 

JPT

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That is the advantage of 3rd members. Do a quick google search for ford 9 inch. You can just drop a third member off, or sell it. Racers will carry several differentials with different ratios, and quickly swap as needed with a few bolts. The pinion gear and ring gear are all assembled within the third member as a single unit.

But in the end, someone still has to set up the gears. It is just easier to sell and deliver.

Really, it usually is the same or a little cheaper to get a professional to regear your axles (rather than buy used/new). You could get it done for about $500-$700 (per axle). Since you are 2wd, that is easy. Then you don't have to do a huge amount of labor (and possibly find out you bought a defective axle).
 
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ilarson007

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That is the advantage of 3rd members. Do a quick google search for ford 9 inch. You can just drop a third member off, or sell it. Racers will carry several differentials with different ratios, and quickly swap as needed with a few bolts. The pinion gear and ring gear are all assembled within the third member as a single unit.

But in the end, someone still has to set up the gears. It is just easier to sell and deliver.

Really, it usually is the same or a little cheaper to get a professional to regear your axles (rather than buy used/new). You could get it done for about $500-$700 (per axle). Since you are 2wd, that is easy. Then you don't have to do a huge amount of labor (and possibly find out you bought a defective axle).

Yeah. Idk, the service manual seems to explain it pretty thoroughly. It's just one of those things that I know I'd be able to do. Maybe not on my own the first time, but it's not like calculus or anything lol.
 

JPT

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Yeah. Idk, the service manual seems to explain it pretty thoroughly. It's just one of those things that I know I'd be able to do. Maybe not on my own the first time, but it's not like calculus or anything lol.

You can do it. But you need tools that cost more than makes it worth it. And if you grenade your gears while on the road, you will need to tow it and reorder parts.

$250 in labor (since you have only one axle to do) is well worth it (even simply just to make someone else responsible for a bad install). You can also ask them to provide you the gear pattern pictures. Make sure they will let you provide the parts (because they are much cheaper online) before you make the appointment. Also be sure to order a MASTER INSTALL KIT along with the gears you need. That includes everything you need for a long lasting install.

I have done 2-3 gear changes, and several locker installs (2 ARB's, 2 Detroits, several lunchbox lockers). Never by myself. I was doing it with club members (my jeep, other jeeps in our offroad club). One of our club members had the tools (he did hes own gear work, and had done about 20+ gear changes over 30+ years.

By yourself, posting gear pattern pictures (so experts can offer their opinion), will take a LOT longer than you expect. You will be without your truck for days.

I am never one to tell someone to not try something on their own, gear work, and internal transmission work are things I generally advise against. Any work that even the average garage will not do, is something that isn't really an easy DIY. Most shops (even dealerships) outsource gear/trans work, and leave it to those with the experience.
 
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ilarson007

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You can do it. But you need tools that cost more than makes it worth it. And if you grenade your gears while on the road, you will need to tow it and reorder parts.

$250 in labor (since you have only one axle to do) is well worth it (even simply just to make someone else responsible for a bad install). You can also ask them to provide you the gear pattern pictures. Make sure they will let you provide the parts (because they are much cheaper online) before you make the appointment. Also be sure to order a MASTER INSTALL KIT along with the gears you need. That includes everything you need for a long lasting install.

I have done 2-3 gear changes, and several locker installs (2 ARB's, 2 Detroits, several lunchbox lockers). Never by myself. I was doing it with club members (my jeep, other jeeps in our offroad club). One of our club members had the tools (he did hes own gear work, and had done about 20+ gear changes over 30+ years.

By yourself, posting gear pattern pictures (so experts can offer their opinion), will take a LOT longer than you expect. You will be without your truck for days.

I am never one to tell someone to not try something on their own, gear work, and internal transmission work are things I generally advise against. Any work that even the average garage will not do, is something that isn't really an easy DIY. Most shops (even dealerships) outsource gear/trans work, and leave it to those with the experience.

My concern then shifts to finding someone who I trust to pay $250 of my hard-earned money to to do this. It's turning out to be much more expensive then I thought it would. Makes me wonder why the engineers went with this design (FYI, "Because that's how we've always done it" isn't the right answer. lol)
 

JPT

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My concern then shifts to finding someone who I trust to pay $250 of my hard-earned money to to do this. It's turning out to be much more expensive then I thought it would. Makes me wonder why the engineers went with this design (FYI, "Because that's how we've always done it" isn't the right answer. lol)

This design is actually very strong. And it is WAY more expensive to design it any other way, just for the few people who want to regear.

Find any offroad shops in your area that work on jeeps. They will do gear work a ton. Any of these shops will be fine. In the jeep offroading world we beat on the gears, so they have to know what they are doing.

What city are you in? I might be able to help find a good jeep shop.
 
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ilarson007

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This design is actually very strong. And it is WAY more expensive to design it any other way, just for the few people who want to regear.

Find any offroad shops in your area that work on jeeps. They will do gear work a ton. Any of these shops will be fine. In the jeep offroading world we beat on the gears, so they have to know what they are doing.

What city are you in? I might be able to help find a good jeep shop.

I'll pm you.
 

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This site depresses me at times. Im very happy with my 4.7 but seems its not up to par with any other truck spec out there.
 

xb1230

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Towing with a 4.7L you're going to want at least 4.10s. Also, I don't believe 3.73s exist for the 9.25" rear axle, that's a gear option for the HD trucks. If they did, it's only a 94 RPM difference at 70 MPH. The 4.7L up to 2007 only has 235 HP stock. It needs a lot more gear to get it moving and maintain highway speeds, even more so when towing. I had an 04 Quad Cab with 3.92s and stock size 33" tires and hated it the first time I hitched up my new boat. I ended up re-gearing to 4.56s and it helped a lot, but still not great with the auto transmission. It soon got traded on a Hemi Ram. That NV3500 manual trans will help some...

With the NV3500, 4.10s would be a good choice since you only have one overdrive gear. Depending on the weight you're towing and the frequency, 4.56s might be better. Here's the ratios of that trans if you're interested.

FIRST 4.02
SECOND 2.32
THIRD 1.40
FOURTH 1.00
FIFTH 0.73
REVERSE 3.55

You have the 9.25" corporate rear axle. Could have LSD (limited slip/anti spin), it was an option. Need to pull the build sheet to confirm. The 8.25" axle is the front axle in a 4x4. You also don't need a whole new axle, just the gears and install kit, then find a good installer that has experience with Dodge axles. Install can run anywhere from $250-500 depending on the area.

Assuming you have stock 20" wheels with 275/60/20 (33") tires, here's your RPMs at 70 MPH in 5th gear.

3.55: 1847
3.92: 2040
4.10: 2133
4.56: 2373

If you have stock 17" wheels with 265/70/17 (31.6") tires, here's your RPMs at 70 MPH in 5th gear.

3.55: 1929
3.92: 2027
4.10: 2228
4.56: 2478

Lastly, speedo recalibration is not required with a gear swap. The tone ring is bolted to the ring gear so a gear change doesn't have an effect.

very educational. I was looking at swapping my 3.92 for some 3.55 but seeing I would gain 100 rpm I don't believe it is worth all the trouble since my diffs are in very good conditions beside some outside rust. All the internals and seals are A1, so I'm not going to mess around this part just to grab a few rpm at 70mph. Especially since the 4.7l is on the anemic side...
 
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