Recent rear axle swap.

[SeaBeeChuck]

Hi folks, need some knowledge. I just finished a rear axle swap on my 2003 3500 dually 4X4 due to the total meltdown of the axle tube caused by bearing failure. Since I am no longer pulling my 40 ft 5th wheel Rv heavy and have downsized I replaced the original 4:10 with a 3:73 I will be swapping the front drive shortly. My question is does my computer have to be changed for the new gear ratio and if so is it a dealer job? Neither my Hypertech or my Edge are giving me the option to change the ratio. Any help would be appreciated. Currently it seems like the shifts are coming in to early especially the overdrive at around 1k rpm’s. Also will the new gear ratio affect the speedometer? Thanks
Chuck

 

[rzr6-4]

Yes, your speedo is now wrong so you will need to have it recalibrated, can be done by dealer or some independent mechanics will do it too.

Your shift points will likely change a little but I wouldn't think it would be too much different. It will be more so do to the new gear ratio changing the torque/load values more so than the computer thinking "ok, I'm at 1K rpms, time to shift" and being too early.

 

[FabricGATOR]

Neither my Hypertech or my Edge are giving me the option to change the ratio. Any help would be appreciated.
Chuck

I presume but I am not assuming... you are looking for "Pinion factor"
just posting in case you didn't recognize the nomenclature

 

[SeaBeeChuck]

Thanks folks for the help. I was pretty sure that it would have to be programmed but wanted to verify.

 

[boatbug]

so on a 2020 ram 1500 big horn 4x4, i want to change from 321 to 392s , what is involved ? is it just front and rear housing units ?

 

[HemiLonestar]

This is 3rd gen; you'll want to ask this question in 4th or even 5th gen (depending on what model you have) as your suspension & axles are quite a bit different.