I got 370k miles on my 2500 Cummings, seal just started to leak, utube videos suggest to mark nut and shaft and change it, others say you have to adjust back lash, then install seal, I'm hoping to just mark it and change seal
What do you mechanics say?

Mic it and and swap is what I've always done, not on that particular rear end though.

Mic it? What's that, mark it ?

Pull it out take it to a guy that knows how to set the ring and pinion and put it back assuming assembled if it has a removable carrier (not a Dodge guy). Some use a crush sleeve some just get X amount of torque if you lack the tools find a guy that knows you will sleep better at night.

Took my work truck into the Ford garage and they put in a pinion seal without being told said it was leaking. I did not make it 60 miles down the road and the ring/pinion was grinding away.

It takes a "feel" to know how much to re-tighten the nut.

Usually i pull the bearing out to get the crush sleeve out and replace the sleeve or do my trick to it to lengthen it and then replace.

Old bearings need less pre-load than new ones.

Rear axle needs to be assembled to set lash or preload? I think

if your not having a noise issue now just mark the nut and the shaft,replace the seal and tighten the nut back up and set to your mark,have done many this way.it kinda takes a feel but youll know when your at your old setting,then just line up your old marks

Some the whole carrier comes out and can be done on a bench not sure how Dodge come apart.

I think you have to pull axles to get gears out, I thought you had to set back lash with it assembled in the housing

Hilltop, kinda what I was thinking, wasn't sure if any change would be necessary with 370k miles, sounds good as far as I know, one guy said to install a speedy sleeve for the probable worn groove in the yoke

You don't have to fool with the axles to put a pinion seal in. The yoke is all that has to be removed.

I Know, Jerry was talking about removing gears to have the back lash set, I think,
I got Valvoline gear oil with limited slip stuff already in it, I think that oil is ok

Ohh, ok.
There is no way for you to change the back-lash by taking the yoke off either. The only thing/adjustment you can possibly change by taking the yoke off is the pre-load on the pinion brgs.

That must be what I meant, I saw some guys on video adjust it, I'll check for bearing play before I take yoke off
Seal seeped a tiny bit a few months back, just yesterday I saw 8-10 drips under it, first time it leaked bad, hope bearing is ok

I would get a new nut
nut should be a locking nut
just to make sure

If you change the nut then you won't know how far to tighten it, I'll just put lock Tite on it

yep

Maybe look into AAA and become a member. LOL I would talk to a Dodge guy as different types of rear ends have their own requirements preload can involve a certain torque, some use a crush sleeve if you get it wrong it can do some damage.

Mic as micrometer, measure. Any time the pumpkin comes out, or ring gears come out, the axles have to come out. Not sure rear end you have.

Sounds like just the pinion seal need replacing just not sure what it takes to load it when putting it back together is the issue it seems.