Mechanic says Rear End Failing??

[Bluebonnet]

Had a rear pinion leak (connecting the drive shaft) that needed a gasket - closer observation showed the differential cover was also leaking despite having just had a new one less than a year ago. Of course the gear oil was drained and replaced at that time - but this go-around (different mechanic who I trust completely) said that the gear oil was really dirty - he even asked me a couple of times - you sure you saw him change the oil?? He said my rear end was failing, that it would need to be replaced soon -

I accepted this diagnosis but the other mechanic, a young guy who actually did the repairs said if I was careful, no long haul trips (I don't/won't pull anything or carry any loads) I'd be ok, maybe even another 100,000 miles. That's a big difference from what his boss said and I'm inclined to believe both of them were being honest - one was being practical the other was trying to make me feel better!

It's summer, I'd like to go up into the woods, maybe some camping. I don't want to get stuck somewhere tho!! Of course I don't need this to fail in the middle of winter either.

Is there a noise or some other indication to watch for when I absolutely have to have this repaired? Is this a safety issue too, that is, can it cause an accident of some sort or what?

 

[Ethan1]

Is it whining or whirring, maybe even a "whoosh" noise? Drive it until it does, then get a new axle from the junkyard for a couple hundred bucks. Who knows how long it will last

 

[turtlevette]

Why does he think it's failing? Too much play? It won't fail all at once. It'll make noise for a long time before the teeth break off the gears and it locks up.

 

[tom slick]

A pinion seal leak could indicate worn pinion bearings. Worn pinion bearings could cause worn gears. All of these could be defined as "going out".

 

[CKN]

Yes, and sometimes a worn rear end or one "going out" will last a long time.

 

[Bluebonnet]

no noise now - just when they reconnected everything and I drove off, not far and a horrible noise was coming from underneath - of course I went back and he and I (the boss mechanic) drove it and this is when he told me it's going out, for now it just needed an adjustment - the torque on the driveshaft - this is also when he told me about the dirty gear oil - he said the bearings were going bad.

after the torque was adjusted it was fine - I drove home (2 hrs, as I made a special trip so this particular mechanic could do this job) everything has been good so far, no more leaks; it's been about 2 weeks now. I only drive weekends (live in the city, use the train) so I don't drive that much. Yesterday I ventured out a ways, about 40 miles round trip, on the highway, no noise, everything seemed fine.

so am I supposed to listen for the bearings then? they'll go first? will they go all at once? I know people can't give definitive answers but whatever can be said that can help me better judge about this is appreciated. it will be expensive to do this work.

 

[cronk]

If it didn't make noise before the pinion seal was changed, but made noise right after, sounds like they might have messed up when they reinstalled the pinion nut and threw the pinion bearing pre-load off.

 

[turtlevette]

Originally Posted By: cronk
If it didn't make noise before the pinion seal was changed, but made noise right after, sounds like they might have messed up when they reinstalled the pinion nut and threw the pinion bearing pre-load off.


I agree. Sounds like the "boss" killed it.

 

[bdcardinal]

Originally Posted By: cronk
If it didn't make noise before the pinion seal was changed, but made noise right after, sounds like they might have messed up when they reinstalled the pinion nut and threw the pinion bearing pre-load off.


Yup, you are supposed to mark the nut in relation to the flange, replace the seal and tighten the nut just a smidge past the mark if you are re-using the crush sleeve. Technically you are supposed to replace the crush sleeve, but that hardly ever happens.

Fortunately the 7.5 and the 8.8 diffs, not sure which your truck has, are some of the easiest to rebuild. Plus since they were in Mustangs, parts are plentiful and inexpensive.

 

[Bluebonnet]

but I took it right back and they readjusted it and it was fine afterwards - !!! it's not making any noises now - and no, it wasn't making any before either - !!



Originally Posted By: turtlevette
Originally Posted By: cronk
If it didn't make noise before the pinion seal was changed, but made noise right after, sounds like they might have messed up when they reinstalled the pinion nut and threw the pinion bearing pre-load off.


I agree. Sounds like the "boss" killed it.

 

[Bluebonnet]

the mechanic said Ford has the specs on the computer and they just look them up and that's what he did. when it made the noise, the boss told him to readjust it a certain way and he did and it was fine and still is !!

no noise!! nada!!

Originally Posted By: bdcardinal
Originally Posted By: cronk
If it didn't make noise before the pinion seal was changed, but made noise right after, sounds like they might have messed up when they reinstalled the pinion nut and threw the pinion bearing pre-load off.


Yup, you are supposed to mark the nut in relation to the flange, replace the seal and tighten the nut just a smidge past the mark if you are re-using the crush sleeve. Technically you are supposed to replace the crush sleeve, but that hardly ever happens.

Fortunately the 7.5 and the 8.8 diffs, not sure which your truck has, are some of the easiest to rebuild. Plus since they were in Mustangs, parts are plentiful and inexpensive.

 

[01rangerxl]

Then it is highly unlikely it is going out.

Not sure why they told you that other than to try to cover their [censored] if they did damage from the misadjustment, but if it's quiet it's fine. If the fluid was real dirty on the last change, the newer fluid won't look totally clean either. There's no filter in a diff. Just a bunch of gears and bearings in oil. If a 7.5 or 8.8 is "going out," it's either leaking a ton of fluid, making a ton of noise, or both. I've never seen a quiet one full of fluid fail in a street driven Ranger.

How do you find these shops? Rangers are definitely not rocket science.

 

[tig1]

Originally Posted By: turtlevette
Why does he think it's failing? Too much play? It won't fail all at once. It'll make noise for a long time before the teeth break off the gears and it locks up.


The teeth won't break off, but bearings will fail.

 

[exranger06]

Years ago, I once had a pinion seal leak on my Ranger. I thought about changing it myself, but then read about pinion bearing pre-load and I was afraid of screwing it up. So I took it to a shop because I assumed they would know how to do it without screwing up the pre-load. I pick the truck up and it's fine. No noises or leaks. Then a a year or two passes by, and 10k miles later, the diff is howling really loud. Bad pinion bearings, caused by incorrect pre-load when the seal was changed. I ended up swapping in a junkyard axle to fix it.

It sounds like your mechanic screwed up when putting the driveshaft flange back on and tightened it up for you. It doesn't make noise now, but there's a VERY good chance he didn't get the pre-load right and it will be making serious noises a few thousand miles from now. At that point, you won't have any recourse. If/when it does start making noise, it won't catastrophically break immediately, it will just make a loud annoying howling noise. You can drive it for a few thousand miles before anything actually breaks.

 

[Nick1994]

I wouldn't be taking differential work to a regular mechanic. It needs to go to a differential shop, they are actually usually priced quite well. They definitely know what they're doing.

My brother re-geared his Jeep's front axle and set the preload wrong and it grinded and made awful noise, so he had to tow it home. We pulled the axle and had a differential shop re-do it and they did a great job. Silent as a mouse now. Didn't cost too much either I think, $300-$400? They replaced the bearings with a kit he had and some seals.

 

[01rangerxl]

Originally Posted By: exranger06
Years ago, I once had a pinion seal leak on my Ranger. I thought about changing it myself, but then read about pinion bearing pre-load and I was afraid of screwing it up. So I took it to a shop because I assumed they would know how to do it without screwing up the pre-load. I pick the truck up and it's fine. No noises or leaks. Then a a year or two passes by, and 10k miles later, the diff is howling really loud. Bad pinion bearings, caused by incorrect pre-load when the seal was changed. I ended up swapping in a junkyard axle to fix it.


Ouch, that really sucks. Hopefully something like that isn't the outcome for the OP.

 

[exranger06]

Originally Posted By: 01rangerxl
Originally Posted By: exranger06
Years ago, I once had a pinion seal leak on my Ranger. I thought about changing it myself, but then read about pinion bearing pre-load and I was afraid of screwing it up. So I took it to a shop because I assumed they would know how to do it without screwing up the pre-load. I pick the truck up and it's fine. No noises or leaks. Then a a year or two passes by, and 10k miles later, the diff is howling really loud. Bad pinion bearings, caused by incorrect pre-load when the seal was changed. I ended up swapping in a junkyard axle to fix it.


Ouch, that really sucks. Hopefully something like that isn't the outcome for the OP.

The thing that sucks is that my truck originally had a Trac-Lock limited slip, and all of the junkyard axles only had a regular open diff, so I had to "downgrade" to an open diff. But I still have my original axle, and I plan on rebuilding it myself when I have the time and money, and I'm thinking of upgrading to a Detroit TrueTrac.

 

[Bluebonnet]

Originally Posted By: 01rangerxl
Originally Posted By: exranger06
Years ago, I once had a pinion seal leak on my Ranger. I thought about changing it myself, but then read about pinion bearing pre-load and I was afraid of screwing it up. So I took it to a shop because I assumed they would know how to do it without screwing up the pre-load. I pick the truck up and it's fine. No noises or leaks. Then a a year or two passes by, and 10k miles later, the diff is howling really loud. Bad pinion bearings, caused by incorrect pre-load when the seal was changed. I ended up swapping in a junkyard axle to fix it.


Ouch, that really sucks. Hopefully something like that isn't the outcome for the OP.

omg - I hope so too!! The owner-mechanic I took it too is really, really good; seriously I totally trust him. He knew immediately what was the problem and told the mechanic who worked on it what to do and yes, it was quiet after as I said. He told me the bearings were going bad - because the oil was so dirty.

The original mechanic who told me he couldn't fix this kind of a leak checked the oil level and it had already gone down a quart since we last checked which was about 6-7 wks prior. So it was beginning to leak more as it wasn't even low enough to add any before and it had been changed last Sept.

This truck has done me well - I've made not one but 2 cross-country trips pulling a U-Haul trailer so there's been some wear on it, no doubt - and of course the bed was loaded both times along with the trailer. That's going over the Rockies, which is not an easy haul. After this last trip I had the tranny oil changed; unfortunately, I didn't know I should have done it for the 1st one or I would have.

thanks everyone for your input I appreciate it.

*question* I did not know about differential shops which some of you mentioned. So there are mechanics who just specialise in this? How do I go about finding one? The original mechanic said he couldn't recommend anyone in our nabe (the Bronx) as so many garages have changed hands in recent years. That's why I went to this other fellow clear over in Pennsylvania - literally 2 hours away, because he's good and I knew I could trust him. I still do. But it'd be nice to find someone closer.

 

[exranger06]

I would search for 4x4 performance shops that install a lot of suspension lift kits and other off-road stuff. Many off-roaders regear their axles when installing bigger tires. These shops probably rebuild a lot of differentials.

 

[01rangerxl]

A quart is a huge amount for the differential to leak, so unfortunately that may have done bearing damage.

All you can really do is keep an eye out for leaks, keep it topped up, and listen for noise.

I agree with exranger06, shops that deal with lifted trucks should be very experienced with differential and driveline stuff or know who is.