2018 F150 rear pinion seal install question

[2013ecof150]

vehicle in question has a Ford 9.75 rear axle.

Replaced pinion seal, and flange due to leakage and a small wear scar on the flange. Marked the nut to pinion with 2 different color markers, but upon tightening of the nut I couldn’t get the nut to line up with the marks. They are about 1/4 inch off on the “ loose side” from being spot on.

Used a medium strength Dewalt 1/2”battery impact to tighten the nut. Stopped as soon as the gun started hammering for fear of crushing the sleeve further. Backlash feels fine when turning the flange by hand. I put the gun on the nut one more time to see if it would turn for just a second, but it started hammering immediately so I stopped.

I counted the threads before hand and there were 2 exposed before and after the repair. I’ve done 4 or 5 of these in the past and never had an issue getting the marks to line up, and I’ve always tightened the nut just a hair more past the marks.

Anyone ever see that happen before? I know you are supposed to measure rotational torque, but I don’t think many people do it that way for a simple seal replacement.

 

[CarbonToast]

I remember when doing mine, I had to impact on it a while to get the marks lined up.

Counting threads exposed is a rough measurement. The marks are the fine adjustment. That last 1/4" probably isn't noticeable in thread count but is for the preload.

 

[CarDoc66]

Hmmm. Possibly because you replaced the flange the threads showing are different because of the machining of the flange.
I usually will do a rotational torque measurement before I take it apart (with the prop shaft, wheels and brakes removed for accuracy).
Most pinion bearings alone spin at 15-30 inch pounds (without the ring gear installed) for a new bearing. Use you judgement from there and go a little further.

 

[2013ecof150]

What’s weird is the last 5 of these seals I’ve done on 9.75’s and super 8.8’s ( they use the same seal and flange) I used the same impact for all these jobs, my truck included, and never had a problem to get that mark lined up plus a little bit more. I installed new flanges on all these trucks as well just because.

The truck in question I would have to unquestionably use a large breaker bar to get that nut to turn a bit more. It’s clear that it’s right up against the crush sleeve currently.

One other thing as well… before I removed the nut the first time I moved the flange side to side just to get a feel for it. Felt a bit sloppy then what I was expecting. Even with the nut just short of the marks on install. The backlash definitely felt tighter.

 

[CarDoc66]

You’re probably good to go, I’m assuming you used OE flange and nut but with supplier changes being the norm these days its probably a bit different. Check it with a torque wrench, 100-125 pounds, if it doesn’t move send it.

 

[thastinger]

What year of these were an issue? My 98 F150 has a Sterling 9.75 rear and an 8.8 front and I've never had any leaks in 200k.

 

[2013ecof150]

You’re probably good to go, I’m assuming you used OE flange and nut but with supplier changes being the norm these days its probably a bit different. Check it with a torque wrench, 100-125 pounds, if it doesn’t move send it.

The flange, and seal were OE but I reused the nut because it had the paint marks on it. I’m thinking it’s probably fine.

What year of these were an issue? My 98 F150 has a Sterling 9.75 rear and an 8.8 front and I've never had any leaks in 200k.

The 18-20’s seems to leak a lot! A coworkers 2020 started leaking before 15k. I replaced my 2019 at 40k. The truck in question belongs to a good friend of mine, and his only has 35k on it.

 

[oldhp]

I've always marked the yoke to the pinion shaft and the nut to the yoke. Turn the nut 1/8" past your marked line. Never had a problem. Was taught this by a old school Master mechanic.