Leaking IRS Pinion Seal

[phileas_fogg]

After 3000+ miles, my T-Bird IRS differential is leaking at the front pinion seal. Replacing the seal appears to be straightforward...if you have a lift. I don't; instead I have questions :D.

1. Can I just add differential fluid, drive for the season, & replace the seal in the fall?
2. When I do the replacement, should I even attempt it without a lift? I know the pinion nut is going to be a bear to get loose.
3. Am I better off just finding a shop that will do the replacement for me?
4. I know a plugged differential vent will cause failure due to pressure buildup, and that a binding drive shaft will cause failure due to excessive wear & tear on the pinion bearings. What other reasons would cause a pinion seal to fail?


John

P.S. NiceGuyEddie: Thanks very much for your threads (https://www.ffcars.com/threads/pinion-seal-leaking-again.296899/); they are very helpful.

[Railroad]

Sorry to hear of the issue. You might check the in and out play on the pinion yoke. You can do this with the drive shaft in place, if the drive shaft is not bottomed out in the trans.
With a pry bar, see if the pinion yoke will move in and out of the diff case. If no movement, good. If it does move you have lost preload on the pinion bearings. You might get by with tightening the pinion nut, just enough to get the slack out, plus about 1/8 of a turn.

If your leak is not too bad, you can add lube and run it, ever how long you can stand it.
If you are having to add much lube, I would say, time to fix it.

To replace the seal you have to pull the pinion flange. In doing this you will lose your pinion bearing preload.
To do this correctly you need to replace the crush sleeve. This involves pulling the rear cover and ring gear carrier to pull the pinion gear.

Back to the seal, if their are no obvious reasons for the seal's failure, I would burnish the seal surface on the pinion flange, with some scotchbrite or similar grit paper, oil the seal with rear lube and install.

Rear lube can migrate out the spline of the pinion gear. It is a good practice to put some rtv on the spline and under the pinion nut on final installation.

An alternative to removing the crush sleeve is to tighten the pinion nut to take up the slack and add addition load as mentioned previously. I have done this and seen it done without issue.

Preload on the pinion bearings yield turn resistance on the pinion in the neighborhood of 25 inch lbs on used bearings. With the ring gear in place you have a minute window to turn the pinion before it engages the ring gear.

You might want to get a feel for it before you unbolt it.

Probably not much help, but maybe something to help you make a decision.

[jrcuz]

Dang John, sorry to hear this. Tom came the other week to change his oil/filter and he said he normally uses the hobby shop lifts on base at Quantico although this may be too lengthy don't know. At my age I think I would be inclined to find a shop I could trust to do it.
JR

[Jacob McCrea]

Good advice above. If the leak is minor and the pinion bearings are tight, I'd just drive it until winter, but do check the bearings more often than not. I have only rebuilt 3, so take this for whatever it may be worth:

I wouldn't let the lack of a lift stop me from doing this. The biggest thing is getting the car high enough to swing a big breaker bar around when setting the pinion preload.

The challenge I think you'll have is trying to get a good read on the pinion preload with it turning the carrier, axles, etc. The Dana 44 I built had a spec for the whole assembly - something like 44 inch-lbs. of resistance with the carrier and axes installed, but no brakes, wheels, etc. If your pinion is tight, maybe take a reading on the rotating resistance of the whole assembly before you tear it down, for a second point of reference.

My understanding of the pinion preload is that it should be taken while the pinion is turning, not at the point where it breaks free of the preload, and the latter number will be just a little higher. I use a Park Tool beam-type torque wrench and watch the beam as I rotate the pinion. I imagine you'd be fine just reading the break-away preload, as opposed to "moving preload," but as noted above, that's not easy to measure when you have (hopefully) .008-.012 backlash with the ring gear.

I built a nice tool to hold the pinion flange, which I'd be happy to ship to you if you want to borrow it.

As for other causes of failure, it could have been damaged upon installation, and just took a while to wear enough to leak. They're not the easiest thing to get straight in the case.

Bottom line: I'd give it a shot. I was intimidated by them until I dug in and figured out what was going on in there.

[NAZ]

I'm too old to be crawling under a car to disassemble a rear end, and even when I was a young stud mechanic I still didn't crawl under a car to disassemble a rear end. Except for those two-speed rear ends Ford use to install in some of the big trucks.

Take it to a Ford dealer where a trained Service Tech will do the job right. I used to be one of those Ford Service Techs and Ford trained me to repair and rebuild rear ends the correct way. I've done my share and have the tools to do the job correctly. Are you willing to purchase some expensive specialty tools that you may only use once? And yes, you will hear advice from people about short cuts and they will swear you don't need to do everything that the service manual directs you to do. But, if you want a job done correctly and you've never done it before, that's not the time to start taking short cuts. The pre-load torque IS an important spec so don't just torque the pinion nut and call it good. And look closely at the surface the seal lip rides on as these are wear items and the condition of this surface can cause leaks if beyond its service life.

UPDATE: I couldn't find this earlier but here is a link that will give you a better idea of how Ford expects you to perform a rebuild of their 8.8 axles. https://performanceparts.ford.com/download/instructionsheets/FORDINSTSHTM-4209-8.PDF

[phileas_fogg]

...Take it to a Ford dealer where a trained Service Tech will do the job right. ...

I think you're saying I should pull the differential & take it to the Ford dealer; is that correct?


John

[Ducky2009]

If you're going to have someone else repair it, find that shop first and ask what they prefer. It takes 140 ft-lbs to torque/crush the crush sleeve. Might be difficult to hold the differential if not in the car. I'd prefer it in the car myself.

PS: I've done it without a lift and it sucks!

[NAZ]

I think you're saying I should pull the differential & take it to the Ford dealer; is that correct?


John

Call Ted Britt Ford (703-659-8409) and tell the Service Writer (or better yet, Serv Mgr) what you have and that your T-Bird IRS is leaking at the pinion seal and see if he can help you. Should be no "real" reason the shop can't put the car on a lift and make repairs on your car. My old dealership would have. Parts Dept probably have the parts in stock but if they had to order I expect they have a source close by. If not, try a race shop such as: https://a1speedandcustom.com/

Good luck.

[phileas_fogg]

Thanks for the clarification NAZ; that's the information for which I was looking. Been a fan of your posts for some time now; you always give level-headed advice.

Thank you Ducky for letting me know that a lift is pretty much mandatory.

Thank you Jacob for the advice & offer to loan me your pinion holding tool.

Thanks JR for your PM.

Thanks Railroad for the advice on checking the pinion play. I plan to do that in the next couple of days.

Cheers,


John