Update: I’m just going to have to bite the bullet and replace the whole diff. I’m getting one with 142k miles on it for a decent price installed. The mechanic said he tightened the pinion nut down to 30 NM torque which is exactly what the book said.
How can i prevent this from happening again though? You can’t always see a leak in the driveway because the seals often will only leak at highway speeds but not necessarily when just sitting, unlike gaskets which will leak all the time regardless of being parked or driving. And in my case there were no noises coming from the diff until it was too late and the grinding sound started at which point major damage had already been done.
So do I just have to check the wheel wells and pinion seal a couple times per week to see if they’re leaking? Seems pretty ridiculous to me…
Wrong book… the Ford factory manual says to re-torque the pinion nut until it returns to the mark he should have placed on the pinion shaft when it came apart AND the rotational drag measured before taking it apart. Once re-assembled, the torque turning the pinion is 1.8 to 3.3 Nm or 16-29 inch-lbs.
If that pinion nut was only torqued to 30 Nm, it was way, way, under-torqued. It should take well over 150 Nm to get the pinion nut tightened back to the place it would match the marks. Took an impact wrench set on high to get mine there. Heck, took the impact set on high plus max psi at the regulator to break the pinion nut free to remove it.
The pinion shaft lock BOLT torque is 35 Nm, but that is the small bolt in the differential itself that keeps the axles in.
Is it EXACTLY the same? If yours had limited slip, does the replacement? Does it have the same gear ratio? If the replacement differential came from a v6 Mustang, it may not be the same.
The 05 to 09 V6 cars had a small 7.5 inch ring gear axle. 05 to 09 V8 cars were 8.8s. All 2010 to 2014 V6 and V8 cars had 8.8 rears. A mix of open, clutch-type diffs and Torsen type diffs in them with several different gear ratios depending on model and transmission.
He said he hand tightened the bolt first with a wrench and then once it wouldn’t turn anymore without having to put pressure then he torqued it to 30 nm.
Because it is torqued until the rotational torque of the pinion shaft and bearings is within spec as I posted before. That is the procedure. You are crushing a sleeve on the pinion shaft to preload the bearings and whatever torque it takes is the one you apply.
And again, that torque is a LOT. 150 Nm plus.
As I said in my very first reply…I doubt your mechanic has the ability to do this work. Now I KNOW he doesn’t.
He thought I was talking about what the book called “differential pinion shaft lock bolt” when I asked him how tight he put the pinion nut. Because taking a glance at the torque specs list there’s nothing else that’s close to that name. Point being, assuming he did all the other steps correctly then it was the part that failed not bad mechanical work.
I didn’t have time to read the entire thread, but I have a Ford truck with a Ford 9 inch differential, and my guess is the mechanic may have made an mistake doing the job. No way to know for sure, it could have been a seal failure too. Rather than casting blame at this point, suggest to just get the differential repaired or replaced. Ford 9 inchers are standard faire. I presume your rear axle has a removable 3rd member. In the future suggest when dealing w/mechanics to not give them the parts; let them obtain the parts themselves.
If you’re saying it needs 150 nm after the sleeve has already been crushed you’re wrong. Obviously from the factory the sleeve is already crushed. So it only takes 20-30 pounds now to fully tighten it correctly if you use the original sleeve, which is the case when you replace the pinion seal. If we were rebuilding the whole differential for instance then you’d use a new crush sleeve and then, yes it would take at least 150 nm+ to crush it and torque the pinion nut down but not for just replacing the pinion seal.
True enough, the Mustang probably uses an 8.8 incher. Ford seems to have stopped making the 9 inchers in the 1980’s, but aftermarket versions are widely available. I’ve always wondered why Ford would choose to make their 9 inch differential themselves, rather than outsourcing the job to a company like DANA? By all accounts however, Ford seems to have done an excellent job.
