Considereing Swapping to 3.73 rear, but ...

smiley · Aug 7, 2014

Programmers have nothing on gears. On gas engine at least Hemi and 4.7L the programmer gains are not that great unless custom tune. I am advocate for gears they make all the difference. Imagine a mountain bike and what happens when wrong gear is chosen. You are dead in the water. Pick a gear better suited for situation and suddenly you can do more power never changes but ratio does.

ilarson007 · Aug 7, 2014

smiley3303 said:
Programmers have nothing on gears. On gas engine at least Hemi and 4.7L the programmer gains are not that great unless custom tune. I am advocate for gears they make all the difference. Imagine a mountain bike and what happens when wrong gear is chosen. You are dead in the water. Pick a gear better suited for situation and suddenly you can do more power never changes but ratio does.

Yeah, I don't do OTS tunes. Custom of the only way to go. Lol.

JPT · Aug 7, 2014

Seriously.... Do the gears... Especially since you are 2wd.

ilarson007 · Aug 11, 2014

Question: If I got an entire differential preassembled, is that not difficult to assemble into the rear end? I am assuming it would be like installing front axles on my Subaru, or any generic halfshaft?

I have a good feeling that I can get a very good (employee pricing) deal on an assembled rear differential, is why I am asking. I am mechanically inclined, as well. FYI

JPT · Aug 11, 2014

ilarson007 said:
Question: If I got an entire differential preassembled, is that not difficult to assemble into the rear end? I am assuming it would be like installing front axles on my Subaru, or any generic halfshaft?

I have a good feeling that I can get a very good (employee pricing) deal on an assembled rear differential, is why I am asking. I am mechanically inclined, as well. FYI

I had a place that would regear for $200 per axle in labor. You bring the gears and master install kit. That will be much cheaper than buying an entire axle assembly new. If you want to just swap, you need to find an axle used on Craigslist or at a junk yard.

ilarson007 · Aug 11, 2014

JPT said:
I had a place that would regear for $200 per axle in labor. You bring the gears and master install kit. That will be much cheaper than buying an entire axle assembly new. If you want to just swap, you need to find an axle used on Craigslist or at a junk yard.

I can do a used rear axle swap myself. Not worried at all about that. I'm also not wanting to buy just a ring and pinion and have that swapped into my differential. I'm just asking about removing my current differential and replacing with a new, pre-assembled unit that has a 3.92 ratio. Is putting the two half shafts in the rear differential, as well as the driveshaft, an easy job, is what I'm asking? Is it only the differential assembly that is the difficult part, as mentioned above? Idk much about trucks, but it seems like sticking the three shafts into the differential shouldn't be hard at all.

JPT · Aug 11, 2014

ilarson007 said:
I can do a used rear axle swap myself. Not worried at all about that. I'm also not wanting to buy just a ring and pinion and have that swapped into my differential. I'm just asking about removing my current differential and replacing with a new, pre-assembled unit that has a 3.92 ratio. Is putting the two half shafts in the rear differential, as well as the driveshaft, an easy job, is what I'm asking? Is it only the differential assembly that is the difficult part, as mentioned above? Idk much about trucks, but it seems like sticking the three shafts into the differential shouldn't be hard at all.

You can't do that. That can only be done with a 9 inch axle... Or any other axle where the gear work is assembled as one unit and then bolted to the front of the axle. With our axles, the gear work is done in the housing. There are shims that place the carrier in the correct position.

You either need a complete axle new or used. Or you have to do/get done the gear work. It is not an easy job.

ilarson007 · Aug 14, 2014

JPT said:
You can't do that. That can only be done with a 9 inch axle... Or any other axle where the gear work is assembled as one unit and then bolted to the front of the axle. With our axles, the gear work is done in the housing. There are shims that place the carrier in the correct position.

You either need a complete axle new or used. Or you have to do/get done the gear work. It is not an easy job.

Seems like this design is much more complicated then it needs to be. The front axles on my Subaru were so easy to change. Knock out the roll pin, slide the axle off the stub poking out of the transmission. All the gear work was internal to the transmission.

JPT · Aug 14, 2014

ilarson007 said:
Seems like this design is much more complicated then it needs to be. The front axles on my Subaru were so easy to change. Knock out the roll pin, slide the axle off the stub poking out of the transmission. All the gear work was internal to the transmission.

Swapping an axle shaft is easy on these axles too. The great work is the hard part. This is what happens when an axle is removed from the transmission.

How did you regear the rear axle on your Subaru?

ilarson007 · Aug 15, 2014

JPT said:
Swapping an axle shaft is easy on these axles too. The great work is the hard part. This is what happens when an axle is removed from the transmission.

How did you regear the rear axle on your Subaru?

I didn't mess with the rear on my Subaru. I replaced front axles after I messed up a CV boot. All you do is remove the axle nut, tap out the roll pin, and pull the axle out of the hub and off the trans stub. Takes like 10 minutes.

I guess I'm not exactly understanding... If I buy a new differential unit from RockAuto (or where ever), I will have to install the pinion to the ring? Which requires properly shimming the pinion bearing according to the service manual.

It also appears, by the service manual, that the rear axle shafts are easy to remove and install. So it *appears* that the only difficult part would be installing the pinion?

ilarson007 · Aug 15, 2014

For reference, here is a picture of what I am talking about on my WRX. The hole in the stub is for the roll pin. That's the only thing holding the axle on transmission side. Then you just slide the axle off. Differential is internal to the transmission.

Additionally, some of the newer models have the stub on the axle and have a female spline on the transmission, but those are just like installing axles into hubs... Except there's no axle nut, I think they just press in.

JPT · Aug 15, 2014

Ok I get it now. You never regeared your subaru. If you did, you would have had the same issues. Re-gearing is not an easy job. There are a few things that you are not used to because you are not coming from axles separated from the transmission.

Axle housing - Metal housing
Carrier - holds the ring gear (it bolts to it) and has spider/other gears inside
Pinion Gear - sits in the housing, is responsible for changing the drive shaft rotation force the ring gear
Axle Shaft - the shaft that slides into the side of the differential carrier that goes from the carrier to the wheels
Differential - A term used that usually means the entire "pumpkin" of the axle housing (without the tubes). Really it just means there is a change in gear ratios within this component.

When you say buy a differential, this is where the confusion is. You can not buy just the differential. Either you buy an entire assembled axle (new/used) with the gear ratio you want, OR you have to buy all the components and install them in your axle housing.

Setting up gears are required anytime you change gears. Think about your picture. The ring gear can move closer to or farther away from the pinion gear (using shims on the entire carrier). The pinion gear can also be moved in and out of the housing. There is a gear pattern you are trying to acquire (picture below with the yellow gear paste). And you want specific pre-load (amount of force required to turn the gears). You also have to setup the pattern for BOTH sides of the ring gear (drive and coast side). There are specs, but it honestly will cost you time and possibly damaged parts if you try to do it yourself the first time.

This image shows all the possible adjustments:

ilarson007 · Aug 15, 2014

JPT said:
Ok I get it now. You never regeared your subaru. If you did, you would have had the same issues. Re-gearing is not an easy job. There are a few things that you are not used to because you are not coming from axles separated from the transmission.

Axle housing - Metal housing
Carrier - holds the ring gear (it bolts to it) and has spider/other gears inside
Pinion Gear - sits in the housing, is responsible for changing the drive shaft rotation force the ring gear
Axle Shaft - the shaft that slides into the side of the differential carrier that goes from the carrier to the wheels
Differential - A term used that usually means the entire "pumpkin" of the axle housing (without the tubes). Really it just means there is a change in gear ratios within this component.

When you say buy a differential, this is where the confusion is. You can not buy just the differential. Either you buy an entire assembled axle (new/used) with the gear ratio you want, OR you have to buy all the components and install them in your axle housing.

Setting up gears are required anytime you change gears. Think about your picture. The ring gear can move closer to or farther away from the pinion gear (using shims on the entire carrier). The pinion gear can also be moved in and out of the housing. There is a gear pattern you are trying to acquire (picture below with the yellow gear paste). And you want specific pre-load (amount of force required to turn the gears). You also have to setup the pattern for BOTH sides of the ring gear (drive and coast side). There are specs, but it honestly will cost you time and possibly damaged parts if you try to do it yourself the first time.

This image shows all the possible adjustments:

So, going back to this picture (below), what am I buying? For example, people sell the entire Subaru differential as a unit on eBay all the time (especially the upgraded model's diff). I was guessing that the "complete" meant that I was buying the entire assembled unit, and just attaching the driveshaft and axles to it.

Here is an example of the Subaru rear end:
eBay link

So, I can't tell from the pictures provided, is it impossible to separate the driveshaft from the pinon? And I can't tell either, do the side gears move around and get messed up after you remove the driveshafts? It seems to me that one should be able to disconnect the driveshaft and axles and pull the differential out and sell it as a unit :shrugs:

EDIT: Why is it impossible to buy just the differential unit? The way the driveshaft attaches to it?

ilarson007 · Aug 15, 2014

I think I found a picture that describes why the differential is not sold as a separate unit. So a better question: Does anyone know what years of the 9.25" rear end interchange with my 04 2WD 1500?

I am assuming that the 2500/3500 do not interchange? Will anything that is labeled "Chrysler 9.25" work?

TylerB · Aug 15, 2014

'02-'08 corporate 9-1/4". The 2500&3500 do not work.

JPT · Aug 15, 2014

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.

JPT · Aug 15, 2014

It usually is cheaper to just regear your own axle. $250-$300 in parts (if you don't add limited slips, or lockers) and $250 or so in labor at a gear shop (any off-road type shop will do gear work).

TylerB · Aug 15, 2014

JPT said:
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.

You can easily swap in a different carrier aka differential (LSD, locker or conventional open) and/or ring&pinion set in to the stock axle. Aftermarket or stock doesn't matter. Lots of confusion in this thread...

JPT · Aug 15, 2014

TylerB said:
You can easily swap in a different carrier aka differential (LSD, locker or conventional open) and/or ring&pinion set in to the stock axle. Aftermarket or stock doesn't matter. Lots of confusion in this thread...

What are you talking about...

You can't just swap carriers without setting up gears. I have seen TONS of ring and pinions blown because of improper setup. Especially for someone who is asking about changing gear ratio to TOW...

There are specifications for specific axles for preload, and backlash. There also are specs for where the ride and coast pattern should be.

This is 100% wrong. DO NOT LISTEN!!!

TylerB · Aug 15, 2014

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

Considereing Swapping to 3.73 rear, but ...

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