Rear axle swap

[BrewKrew]

Will a 2008 2wd 3.92 half ton rear axle fit plug & play into a 2005 4wd half ton truck? They’re getting hard to find

 

[HemiLonestar]

Should be the same, so long as the ratio matches.

 

[kevkev]

I think front axle has to be geared the same or you'll grenade your transfer case?

 

[BrewKrew]

Okay so I guess next question is how to 100% find the gear ratio? I marked the driveshaft and turned the rear right wheel, I got 3 whole turns and at least 3/4 on the 4th. It wasn’t super close to 4 like I would expect 3.92, but i’m pretty sure it was more than 3.73. There’s a little play between the wheel and the driveshaft’s rotations. I put my vin into a build list generator and it said 3.92 FRONT gear ratio, but it also said 20” wheels, which is incorrect for my truck, it has 17’s and they’re stocks so they’re probably original? It’s a 2005 ST 4.7 4x4 with 5 speed auto. It’s old and worn and I can’t justify paying 2-3k for a shop to do this for me.

 

[Daw14]

Pull the cover off and it will be marked on the ring gear . You may need to rotate the driveshaft in order to get the correct position to see the numbers.

 

[Wild one]

Okay so I guess next question is how to 100% find the gear ratio? I marked the driveshaft and turned the rear right wheel, I got 3 whole turns and at least 3/4 on the 4th. It wasn’t super close to 4 like I would expect 3.92, but i’m pretty sure it was more than 3.73. There’s a little play between the wheel and the driveshaft’s rotations. I put my vin into a build list generator and it said 3.92 FRONT gear ratio, but it also said 20” wheels, which is incorrect for my truck, it has 17’s and they’re stocks so they’re probably original? It’s a 2005 ST 4.7 4x4 with 5 speed auto. It’s old and worn and I can’t justify paying 2-3k for a shop to do this for me.

Odds are it's a 3.55 as that was a very common ratio for the 4.7 trucks

 

[HemiLonestar]

Likely your diff ratio hasn't been changed, run your VIN (might also be in the glovebox if the sticker is still there).

 

[Harry Paratestes]

Should be the same, so long as the ratio matches.

2wd rear axles dont have bump stops like the 4x4 ones is the only difference I know of

 

[Recoil]

2wd rear axles dont have bump stops like the 4x4 ones is the only difference I know of

I also believe that there's a slight difference in distance where the shocks mount between a 2 wheel drive axle and a 4 wheel drive axle.

 

[Harry Paratestes]

I also believe that there's a slight difference in distance where the shocks mount between a 2 wheel drive axle and a 4 wheel drive axle.

Have you confirmed this for sure? Would like to know as one of my 4x4s might need an axle swap in near future and i know of a 392 limited slip one for a good deal but it's 2x4

 

[Recoil]

Have you confirmed this for sure? Would like to know as one of my 4x4s might need an axle swap in near future and i know of a 392 limited slip one for a good deal but it's 2x4

When I called around to get a replacement for my (former) 2003 Ram 1500, I was asked specifically if it was 4x2 or 4x4 due to the slight differences in shock mounting location. I made sure to get one for a 4x4 since that's what I had.

 

[Sherman Bird]

Will a 2008 2wd 3.92 half ton rear axle fit plug & play into a 2005 4wd half ton truck? They’re getting hard to find

I'd make sure that the width of the 2 assemblies are the same.

 

[Harry Paratestes]

When I called around to get a replacement for my (former) 2003 Ram 1500, I was asked specifically if it was 4x2 or 4x4 due to the slight differences in shock mounting location. I made sure to get one for a 4x4 since that's what I had.

Interesting