Hello All;

I recently changed the pinion seal on my '97 Expedition. It has the 9.75 rear end with 3.73 gears and limited slip. I included the 8 ounces of friction modifier (it was Ford black bottle) with the synthetic oil. I replaced the cover, because the original was heavily rusted. Everything inside looked okay - but, I have no idea what looks like a good wear pattern or not. Nothing appeared cracked, broken, misaligned, and there were no bits in the housing.

Now, I have a whine during deceleration. I can't tell if I have one during load - but, when I back off the engine and we're coasting, there's the whine. I runs down to about 20mph, where it generally disappears. I had the vehicle to 55-60 and coasted down to 30 and it whined the whole time.

There was no sound before I did this work - at least none that I was concious of.

So my questions are this:
A) Have I wrecked it?
B) Will driving it with the whine wreck it?
C) Do I need to learn to live with the radio at a louder volume?
D) Is there something I can do to make it quiet again?

Thank you,

David

 

Welcome ! A common symptom of improper pinion bearing preload is whine under deceleration. If you had no whine before the seal replacement, then the pinion bearing is probably ok.

 

So you must have changed the fluid. Did you notice anything like sawdust in the old fluid.

 

Max - okay, so I possibly have improper pinion bearing preload. How can I correct it? Also, I assume I should avoid drving the vehicle for any distance until I get it corrected - correct?

Larry - yes, I changed the fluid and it came out looking okay. One thing I should point out is that the seal had been leaking for a while. Once I completed the seal replacement, I topped off the fluid with almost a quart of straight synth oil and took it for a drive around the block and heard the whine. Figuring that I was going to replace the cover and do a full fluid change, including the friction modifier, I assumed the noise would go away...that didn't work out like I'd hoped.

Thanks,

David

 

All;

A little update. Took the beast on a drive to the local grocery store (about 5 miles away) so that I could listen to it again. It does appear to have a whine while accelerating in the 40-50mph range. Not nearly as noticable as during deceleration, though.

So, is it time for me to shell out serious dollars for a new rear-end?

Another point, the beast has 135K on the driveline...

David

 

You have not "wrecked" your rear end. It's not optimal to drive it this way, but it's not going to fall apart. What exact procedure was used to set the pinion bearing preload?

 

edit-double

 

Max - I guess I didn't. I followed the basic guidelines in the Haynes manual for the seal replacement. I don't own a inch pound torque wrench, so, I didn't take that reading...and I guess that's where I went wrong. I also didn't take the rear wheels off the car - I did the work with the rear end on ramps. I counted the number of exposed threads and used the pinion nut the reseat the flange until I had that many exposed threads again. And stopped there.

Nothing like looking into a DIY maintenance manual and hearing friends say that the pinion seal is a no-brainer job to convince you that you can do it in your driveway...

David

 

David,
Some of this you won't want to hear. The proper way to set preload is with the differential out of the housing. With only your pinion assembly in the housing, you set the preload based on used or new bearings. Once your original pinion nut is removed, your preload is reset with a NEW crush sleeve and a NEW pinion nut. The preload for USED pinion bearings is only 6-8in./lbs and this specification is for the pinion assembly being installed alone in the housing. You can't read a few in./lbs. accurately with the gauge turning the differential, axles, wheels, and with brake drag. It's also hard to measure an accurate preload before disassembly this way. Counting pinion threads or pre-checking original pinion nut torque while assembled, then re-torquing to that spec, is guesswork. The procedure and sound that you describe could likely be a loose preload. You may get lucky and be able to increase your preload SLIGHTLY and shut the noise up. "Slightly"...several small increases would be better than over-torquing. At this point, I would consider this guesswork at best. As you re-installed your pinion nut, did you take a torque reading? Did you get the feeling that the nut was going on easily and then got tight at the end?

 

Max - thanks for contrinuing to read and reply. Your most recent comments merely confirmed my fear on my improper installation job. I wish that Haynes had included some additional information about this. They certainly excluded the information on doing a full overhaul for the differential assembly saying that specialized tools make it impractical for the DIY mechanic to tackle the job...

Today's update: I drove the beast into work (approximately 28 miles), and it made noise the whole way - big surprise, right. I decided I would chalk this up to lessons learned and take it into the dealership. So, I did...the local Lincoln-Mercury dealership took my car in and confirmed everyone's diagnosis. They "torqued things down to spec", but they did not take the unit apart and put in a new crush sleeve...so, perhaps I've gotten things squared away and perhaps not. I received my car with the disclaimer from the dealership that "pinion bearing failure may occur at some point in the future".

The noise is gone - which is what I'm most interested in. The driveline has 139K on it (thought it was still around 135K...) so, a full overhaul is probably in the future in the next year or so.

So, my DIY save me some money approach still cost me $130 and a trip to the dealer in the end. The moral of the story here is to read my DIY manual, to see if I feel I can tackle the job, then research the job on the internet (in places like this one) to see what the pitfalls are and weigh it out.

At the moment, my whine in the differential appears to be gone. So, I feel a little better about the need to take the vehicle on a long trip later this week.

Wish me luck that the dealership didn't take me for a ride with a short cut that will cost me in the long run.

Thanks to all,

David

 

You're more than welcome. I had an initial feeling that things would go this way. Just let some time go by and focus on the positive; no whine, no damage, new seal, new fluid, etc. Good luck with it.

 

Max - I'm already focused on the positive, but thanks for the sentiment. Heck, when I tore into this project, I came the realization that it was worth my time...but, I was sort of committed since it was already in pieces. It does make for a funny story, though.

David

 

You can only get better and better.

http://www.guru-international.com/lo...ves/000871.php

 

You will never learn anything if you don't try! This time you learned a lot. Education is expensive.