Differentials aren't only in calculus

[shamaal]

Well poop, it's always the stuff I know nothing about.

Turn left at a stoplight outside work parking lot and hear a crunching sound in front. Pull into the parking lot at work, look under the car and a couple drops of oil are under the front differential. All in all the car had about two blocks on it with an occasional crunching sound when turning the wheels while moving. No noise turning wheel while stopped.

Plan tomorrow is to fill differential with oil, drive around parking lot, hope for no noise and limp eight miles on home. If noise I'll probably get tow from AAA.

1. If differential is dry does crunching when moving and turning sound like a symptom?

2. Where's the leak? There is oil around passenger axle seal but this looks like a real leak. Is there a seal for the cover?

3. Ujoints feel tight, but I know that doesn't guarantee they haven't seized. Vehicle has 140K on it.

4. There appears to be a disconnected hose atop the differential, I assume that's a vent?

I've located enough search threads (out of 1272) to remove differential, so thanks to anyone who can provide advice.

 

[Exploderpilot]

weird. could be chewed up gears, but who knows till you open her up. here's some questions.
did the sound have a rythym to it at all? what about the front driveshaft? is there grease on the slip fitting? did you check the axle joints?

 

[IZwack]

A differential that crunches typically means there's something horrific going on inside the differential (not just the absence of oil).

I've heard a few differentials being driven after "grenading" (shattered carrier, sheared center pins, etc..) and the sounds are terrifying. I think its best that the vehicle be towed home instead of driving it another 8 miles. The differential unit will work perfectly fine going straight but it will probably destroy itself even more during turns.

 

[shamaal]

No rythym at all. Only when turning and it's not constant crunching. Keep in mind I've only driven a couple blocks in a parking lot never over 20 mph since I first heard it.

It's possible gears are torn up and that's why I'm noticing it now. Axle joints are tight not loose. There is a leak at the axle seal from moisture on the dirt. Driveshaft is dry and tight.

 

[shamaal]

A differential that crunches typically means there's something horrific going on inside the differential.

I've heard a few differentials being driven after "grenading" (shattered carrier, sheared center pins, etc..) and the sounds are terrifying. I think its best that the vehicle be towed home instead of driving it another 8 miles. The differential unit will work perfectly fine going straight but it will probably destroy itself even more during turns.

Yeah, I'm kind of hoping it will fix itself when I put oil in it, but then I have a firm belief in the Easter Bunny also.

Thanks Senator.

 

[Exploderpilot]

terrifying is exactly the word to describe the sounds when my rear end blew up last year. TWICE!!! once jumping on the beach, and i drove it home, kicking and bucking all the way. as i would go around turns, it would randomly grab and bang and slam the truck around. it sucked. i would definitely not move that thing.

 

[IZwack]

If you can't get the vehicle towed and you're out of options, you could remove the "dog gear" from the hubs and the disconnect/remove the driveshaft -- that should stop the differential from rotating which would allow you to get the vehicle home w/o doing any more damage.

 

[Exploderpilot]

and if there are chunks of metal rolling around in there, you don't want that mess eating the ends of your shafts, or ruining the carrier or anything not broken yet!

 

[scucci]

Disconnected vent line would be a cause of low oil level. Noise when turning would be a differential side gear/spider gear problem. Maybe you'll be lucky, but it sounds as though the damage is already done. Sounds as though might need to rebuild or replace the diff.

Scucci

 

[IZwack]

Disconnected vent line would be a cause of low oil level.

I am somewhat doubting that a disconnected vent line would cause low oil level. But I have no experience with the TTB so please school me if I'm wrong (I dont even know where the breather tube is!)

A differential's fill plug is often located about halfway up to ensure half of the ring gear is submerged in oil. If the breather tube is on top of the differential housing, then the oil voume would have to expand another maybe 50% in order to reach the breather hole (lets say during some extreme cornering where the oil is pushed to one side).

The Ford 8.8 axle is often seen with oil stains around its breather tube because its breather tube is on the axle tube (driver's side) -- not on the differential housing. Therefore, without having inner axle seals, the oil in this axle can reach the breather tube when the axle is off-camber (driver's side down).

 

[shamaal]

Thanks for the replies, according to Haynes differential oil is API GL-5 SAE 90 Hypoid gear lubricant.

It looks like I may be in the market for a differential replacement.

Oh joy!

The pisser is, I haven't found anybody with a roadster in stock so I could replace the Navajo. Now I'll end up fixing it to give it to charity.

I got a line on a new Miata up near San Antonio, but it won't be in for a couple weeks. It's hard to feel sympathy for car companies that don't/can't/won't make enough products that sell.

 

[unclemeat]

I am a little confused, front differntial? If the hubs are unlocked and the the transfer case is in 2wd then the front differntial shold not be turning, at least it does not on mine.

 

[shamaal]

I confess that I am somewhat ignorant of the workings of my 4WD. I've only used it 3 times since 1990. My working theory right now is that the wheels, front axles and front driveshaft are engaged all the time and the 4WD button engages something in the xfer case.

If incorrect let me know. Although now that I think of it the front wheels do freewheel when not engaged so the working theory is wrong. Maybe I'll jack up each side in the parking lot and see if the wheels freewheel. How does the 4WD engage the front hubs on the 91's. I don't recall any vacuum lines going to the hubs.

 

[glfredrick]

Hey Shamaal, how's it going?

I'm surprised that no one has mentioned the REAL danger of a messed up differential -- the potential that it will lock up solidly at any time, likely causing serious damage, not only to the differential, but to the car and its driver.


On a 91, the differential does not turn all the time. You likely have the auto hubs, which can go bad and stay locked in, but more likely when they go bad, the refuse to lock in at all (most typical scenario).

There was no option on a 91 for a full-time transfer case, so if you are not in 4x4, there is no action at all at the front end at all.

I might be inclined to check front wheel bearings, which are well known for getting loose and/or worn past servicable life.

If it turns out to be a differential, your easiest fix for the front end is to get the entire "pig" (the aluminum housing complete with carrier and gears all ready to bolt to your steel axle housing) from a salvage yard vehicle. Make sure the gear set matches the ones out back and after that, it is a bolt in proposition.

I can get one for you and ship it to you if need be. We have a huge selection of Explorers at the local pull-a-part and prices are reasonable enough to make it worth the effort.

 

[wood1]

My '93 XLT had a similar issue. MY guess is that if you remove your auto locking hubs you will be able to drive home. My u-joints were seized so badly that when I cut the wheels the u-joints would cause a misalignment in the hub and it would try to engage itself causing a terrible crunching sound. The u-joints seemed fine tugging on them while installed, once removed it was a different story.

Pull your front wheels, remove the hubs and put your wheels back on. Chug around the parking lot a bit, hopefully that is your problem.

C.

 

[IZwack]

x2 -- there's a chance its just the hubs thats acting up, so pull them out and drive it home.

 

[shamaal]

Thanks guy, I see you posting occasionally at DMI.

I originally thought that the differential does not engage in 2WD but talked myself out of it when I saw the oil leak. The vehicle hasn't been in 4WD (buttons pushed) in at least 5 years.

The oil leaking from the differential may be a red herring, I'm headed over there now with new oil to see what effect that has. The wheels are tight, but I may be in the early stages of bearing disintegration. We had flooding earlier this week perhaps the grease got washed out. I'll jack up the wheels and check for play.

 

[shamaal]

x2 -- there's a chance its just the hubs thats acting up, so pull them out and drive it home.

Ah, you guys make it sound so simple.

What is involved with pulling out hubs? See pic below. I'm guessing removing the snap ring, axleshaft spacer, cam and plastic thrust spacers; then stopping before the wheel bearing nut or do I just remove the hub (like the instruction said) and that's it?


Maybe I'll get luck and the wheel bearing's disintegrating.

 

[wood1]

When you pull the front wheel off, the hub will most likely come off with it. Just put the wheel back on without the hub.

C.

EDIT: You won't have to remove the snapring and cam ass.

 

[shamaal]

I can do simple. Thanks W1 glf and IZ! I'm off to the lot.