1994 f250 4x4 460 5 speed


i just replaced the rear pinion seal on my sterling 10.25 and I think I overtightened the pinion nut. When I drive my truck all is well when I have my foot on the gas, but when I put the clutch in I can hear/feel some pretty sever vibration from the drive line. I know there is a crush washer in my rear diff that I’ll probably have to replace now, but does that mean I have to tear down my rear diff?

 

To set up pinion bearing preload correctly, yes. Remove axle shafts, remove rear cover, remove differential carrier, remove driveshaft, remove pinion nut, use puller on pinion flange, carefully remove pinion gear from the axle housing. swap to a fresh crush sleeve. Would be a great time to replace pinion bearings if there's any question about them. If you do replace bearings, just be sure to re-use the OEM pinion shim that sits under the inner pinion bearing. While tightening pinion nut, once all the end-play is gone, begin checking torque required to rotate the pinion with an inch pound beam style torque wrench. Used bearings should be a little easier to rotate than new; there is spec for this. If you over tighten, remove pinion, install new crush sleeve, try again.

Because you've likely run with truck with too much bearing preload, I would go ahead and replace the bearings. Last time I took the short-cut seal replacement method (e.g., only swapped seal, didn't pull rear end apart for new crush sleeve), I over tightened my pinion too and destroyed bearings (cracked the rollers). I know some people swear by that method but it's never worked for me.

 

Thanks for the detailed write up. I’m not sure that I have the tools or know how to be able to set the backlash and bearing preload. It this job a simple pull and replace?

 

It's not too bad if you're reusing the differential carrier and gear set, but you need some patience and attention to detail. Just be sure to keep all shims in original locations. Gear pattern should not change if you do it that way (because pinion depth & backlash won't change), so it's not like setting up a rear end from scratch. The toughest steps in my opinion are removing the inner pinion bearing from the gear (I've had to cut them, as I don't have a bearing splitter or clamshell or shop press), pressing on the new bearing (unless you have a press, then it's easy: I don't..), and being patient about incrementally tightening the pinion nut while checking break away torque so as not to go too far. The inch-pound beam style torque wrench and a pinion flange holder were the only tools I didn't have. I don't know if the Sterling 10.25" needs a case spreader to install the carrier; the 8.8" does not.

It's also possible you don't have the pinion nut tight enough. How did you determine how far to tighten the nut after seal replacement? Did you use an impact or a breaker bar?

 

I used an impact, I’m thinking it’s possible that I didn’t tighten it down enough. I used a torque wrench to check the ft/lbs and couldn’t get it to click at the 150 ft/lb setting, so I thought I had it tight enough.

 

In my experience, 150 ft.lb isn't enough to further collapse the crush sleeve. But I'm not sure what you mean by not able to get it to click at 150 ft/lb setting: did it just continue turning/tightening?

 

I was on my back and couldn’t get the leverage to move the nut any further with my torque wrench set at 150 lb. I found that spec cruising this forum a few months back. Should there be any amount of play in the pinion after the nut is correctly torqued?

 

Don't need the torque wrench, when changing a pinion seal you mark the nut, yoke, and pinion then count how many turns it takes to get the nut off, then remove the yoke, replace the seal, the put the yoke back on in the exactly where it was before then put the nut back on with the same number of turns until it lines up with the mark you made.

 

^^Yeah, that's the quick and dirty way to do it, seems to work for most people. But kind of a moot point now, as it doesn't sound like he marked it before disassembly. If doing it that way, I'd use lots of thread locker.

The trouble is, without a prior reference mark, or pulling the differential, it's going to be very difficult to know when the pinion is tight enough, because that's judged by torque required to rotate the pinion without the ring gear in contact (I'll call this breakaway torque). Typical value for that would be (ballpark) 15 inch pounds on used bearings. The torque on the pinion nut to achieve the bearing preload that produces correct breakaway torque is substantial, but there is no set spec, it completely depends on the material the crush sleeve is made of, and no matter: the only thing that matters is reaching the specified breakaway torque. Pinion nut torque is likely on the order of 250+ ft lbs. I usually put a cheater bar on my 2' breaker bar, hold the pinion with a heavy piece of flat stock bolted to the pinion flange, and it's still a work out.

If there is any play in the pinion, there is effectively zero preload on the bearings, meaning you're not tight enough yet. If your torque wrench set to 150 ft lbs never clicked, I bet the vibration/chatter is from a loose pinion.

 

I did mark the pinion and the nut before replacing the seal, so maybe I should keep tightening until the marks match up and the break away torque is 15 lb? Can I use that measurement with the axle shafts in and wheels on?

 

If you marked the pinion nut, continuing to tighten until you line the marks up is your best bet. Having the pinion flange in a different position than before is maybe going to throw it off a little but probably not significantly. If you're off a full turn, hopefully its obviously not tight enough and you know to keep going. It's harder to say how to know about going too far (since it sounds like you didn't count turns to remove the nut, as suggested in post #8).

No you cannot measure the break away torque with the axle assembled. It's ~15 inch pounds, not foot pounds. So the additional torque required to turn the differential carrier bearings, the axle shafts, axle seals, and wheels & brakes would scramble or drown-out the pinion break away torque. The carrier would need to be removed.

Either it works and you're good to go, or it doesn't and you end up having to start over (maybe with new bearings). Not much risk there, cost is maybe a couple bearings, a pinion crush sleeve, and you learn some stuff.

 

GB thanks for all of the help. Ill keep going on the pinion nut and see if I can't get it back into spec. If not, it's like you said: A few parts and a lesson or two.

Thanks again.
-PVZ

 

It sounds like you went BEYOND your mark already

 

If that's the case, he'll need a new crush sleeve and re-set up the pinion preload. I just don't think that would be possible with under 150 ft lbs applied to the nut. Certainly could be wrong, but he's got little to lose at this stage.

To the OP, you're welcome. Hopefully it's just a matter of going a little tighter.

Something else you should know, if you do overtighten the nut, you've permanently over-crushed the crush sleeve, and can't just back the nut back off. The only way to make it right is drop in a new crush sleeve and start over.