Rear Differential Leak -- Vent

[B-n-B]

Hi All, me again ...

Got the call back from the local Toyota dealer. It's not as good as I would like, but could be worse (a little under $1k ... kinda surprising since the Lexus dealer did their check over and fixed a bunch of stuff)

The one item that I don't know anything about ... they said there is a rear differential leak, and that the "vent" is frozen/locked and needs to be replaced. I went to lexuspartsonline, and managed to find the differential parts category, but nothing in there says vent ... the lady at the dealer didn't have a part price, but they said about 1 hour of labor.

I got a 1K mile / 1 month warranty on engine/drive train/transmission from the dealer I purchased it from ... it seems like this would count in that bucket, right? I just hope they don't make me take it back to their location ... need to read over the paperwork tonight.

Is this a serious thing? Could it be an indication of larger issues (i.e. should I make the local folks dig into it more in case it's a something that I could get fixed under my very tiny warranty), or is it just something that wears and I shouldn't be concerned?

Thanks so much!

[jcrome04]

Yes the differential is part of the drive train! Get any service covered under that warranty that you can. Probably used up a lot of those 1k miles on the 6 hour drive home huh??

[Threadcutter]

Hi All, me again ...

Got the call back from the local Toyota dealer. It's not as good as I would like, but could be worse (a little under $1k ... kinda surprising since the Lexus dealer did their check over and fixed a bunch of stuff)

The one item that I don't know anything about ... they said there is a rear differential leak, and that the "vent" is frozen/locked and needs to be replaced. I went to lexuspartsonline, and managed to find the differential parts category, but nothing in there says vent ... the lady at the dealer didn't have a part price, but they said about 1 hour of labor.

Thanks so much!

B-n-B:

My BS Alarm is going off at about 118 decibels!...............

I think you're the lamb and they're planning a "party" in your honor.

The differential holds roughly 1 to 2 quarts of 90 weight gear lube (we can argue the finer points later.....). If it hasn't been slobbering gear lube all over your garage floor or driveway, chances are very good you're being hornswaggled by the dealer. If I were in your shoes, I'd tell them to hold off because I couldn't afford the bill. I'd take it home and crawl up underneath it and caress (excuse me, I'd run my hand all over) the differential. If I didn't come back with a slimy mess all over my hands, I'd know for certain I was being lied to.

The differential may even be sealed, I don't remember for certain. There are others smarter than me on this board who will chime in and tell us for sure.

There probably is a vent. If it is plugged/clogged, it might be as simple as giving it a good going over/through with a pipe cleaner. I've never heard of a clogged differential vent though. If there were enough pressure build up in the differential to cause leakage, it would have blown the clog out of the vent before it ever leaked. It also could be as simple as someone having overfilled the differential the last time the lube was changed.

I have a 2000 Suburban that definitely has a leaking front differential. Every 5000 miles I top it off with about 100 to 200 cc's of 90 weight. Not what you want to do with a luxury car, but it's not like you're sitting on top of a bomb with 3 seconds left on the timer.

Oh and if they tell you that you need a new throttle body, run like hell.

[chilkoot]

I don't recall ever hearing about a vent, as far as I know there are only two ports on the differential, the drain and fill plug; otherwise it is sealed. A vent wouldn't really have any function as I understand it.

Aren't the differentials a fairly simple gear system? I don't see how a "leak" could be anything more than a simple seal, it's at the rear end of the car, it's not like it's hooked up to a pump and a reservoir.

[nc211]

Threadcutter, good too see you again my friend! I love that part about needing a new throttle body!

My guess: if it's leaking, they probably didn't use a new crush washer on the drain plug. I have never heard of a "vent" on a rear differential. It doesn't sound like it would make sense to have an opening on a differential, which would allow debrie and moisture to get into it. From my standpoint of my old 95, and current 05' 4runner with two differentials & transfer case, neither one had/has a "vent". It's a fill plug on the top, a drain plug on the bottom, with seals along the axles into the unit.

But to answer your question about the warranty: As mentioned by the former rookie-now all grown up-jcrome, YES-IT'S ABSOLUTELY covered under that warranty. You might have to argue with them a little to get them to pony up, as they tend to hate to pay for things on their own. But, it's part of the driveline, and if they say anything different, then ask them how in the hell a driveline could possibly work without a differential? No differential, then all you have is a driveshaft hanging down under the car.

If you don't want to go all the way back to the dealership for the service, just call Lexus corporate and see if they'll allow your local toyota dealership to do the repair, on the lexus dealership's dime. This is a very easy DIY repair, if you're a diy type. I've flushed differential fluids in both cars several times. The only hassle is that the fluid stinks to all highhell. The dealership will drain the fluid, clean the drain plug-which has a magnet on the internal end to hold any metal shavings that naturally happen, put a new washer on the plug, put it back in, and fill it up from the top port "which too has a plug". Any shop can do it, takes 20 minutes, tops.

But first, just look under the car and see if the bottom of the differential is wet, or the axles. If it's just the differential, then it's most probably just the plug "or excess fluid from the change". If the axles are wet, then you've most likely got a worn-out seal, which you'll want the dealership to fix under the warranty. BUT, I would be stunned if it's the seals at this mileage and age. There have been few to no differential seal leaks posted up here that I can recall in the 3 1/2 years I've been on here....even Chilkoot's rear differential seals weren't leaking when he bought his neglected LS he has now "brought back from the dead". Right Chilkoot?

PS: After seeing your other thread with the pictures, I'd not be suprised at all if the dealership is trying to snake a few extra bucks out of you, for giving you such a good deal!

[wwest]

Threadcutter, good too see you again my friend! I love that part about needing a new throttle body!

My guess: if it's leaking, they probably didn't use a new crush washer on the drain plug. I have never heard of a "vent" on a rear differential. It doesn't sound like it would make sense to have an opening on a differential, which would allow debrie and moisture to get into it. From my standpoint of my old 95, and current 05' 4runner with two differentials & transfer case, neither one had/has a "vent". It's a fill plug on the top, a drain plug on the bottom, with seals along the axles into the unit.

But to answer your question about the warranty: As mentioned by the former rookie-now all grown up-jcrome, YES-IT'S ABSOLUTELY covered under that warranty. You might have to argue with them a little to get them to pony up, as they tend to hate to pay for things on their own. But, it's part of the driveline, and if they say anything different, then ask them how in the hell a driveline could possibly work without a differential? No differential, then all you have is a driveshaft hanging down under the car.

If you don't want to go all the way back to the dealership for the service, just call Lexus corporate and see if they'll allow your local toyota dealership to do the repair, on the lexus dealership's dime. This is a very easy DIY repair, if you're a diy type. I've flushed differential fluids in both cars several times. The only hassle is that the fluid stinks to all highhell. The dealership will drain the fluid, clean the drain plug-which has a magnet on the internal end to hold any metal shavings that naturally happen, put a new washer on the plug, put it back in, and fill it up from the top port "which too has a plug". Any shop can do it, takes 20 minutes, tops.

Almost all rear diff'ls have a moisture/vapor "vent". The idea is if water does happen to get into the diff'l it will vaporize under heat and the pressure will drive the vapor out of the vent, just like EVERY headlight and tailight assembly. Look for a small rubber hose (like for engine vacuum) coming out of the diff'l case and often ending into some body or suspension structure such that there isn't likely to be any reverse flow if you drive through a puddle, stream, river. (river...??)

In the alternative you might have a small spring and ball checkvalve to let vapor escape under pressure. These would be near the top of the diff'l somewhere and covered (hidden...) by a metal cap to prevent the checkvalve from getting contaminated with roadway debris. If the spring/ball checkvalve were to fail "open" you might very well end up with no lub in the diff'l, eventually.

And by the way the fallacy, minor fault, in converting tailights to LEDS is you will get no heat/cool pumping action to remove moisture inside the taillight (headlight..??) assembly.

[nc211]

Interesting! I didn't know that west! I've learned something new today

[VBdenny]

what did you see when you looked at the differental?

[B-n-B]

I haven't had a chance to look at it (it's been at the dealer since Monday AM), and hubby is out of town.

The warranty dealer offered to pay to have the vent cleaned, not replaced. Apparently the cleaning is about $90 ... the replacing is $120 ... so, I said "how about I pay the extra $30 and have it replaced." ... the service coordinator indicated that it was actually better to not replace it, but instead clean it. This sounds somewhat suspicious to me, so I called another Lexus dealer service guy and he said that cleaning it is putting a band-aid on it .. much better to replace it, especially if it would only cost me the difference, since it will at some point wear out again.

ARGH! You guys have any opinion about who is right?

Thanks a ton!

[B-n-B]

I called back and demanded more information. The story is that the replacement vent part has to be "bent" to fit into the "hole" and it will never be as good or as tight of a seal as the factory original. She did say that if cleaning doesn't fix it, the warranty dealer did offer to pay to replace. I feel a bit better.

sorry for all the questions!!

[VBdenny]

Sorry? why?

This was a good topic and an issue I had never before heard of. I dunno, it just sounds to me like you are getting some kind of run-around. The very first thing I would do would be to put the car up on ramps or a lift and do a look-see. IF the thing is leaking you would certainly see oil around the area indicitive of a problem no matter what the cause. But, if there is no fluid leak apparent, I would unscrew the fill plug (use a 1/2 drive breaker bar or ratchet with a short extension. Then dip a finger down into the hole and reach down as far as you can and see if you come up with any gear oil. If you do, then they are most likely BS'ing you.

Sometimes cars are such a pain and the people who work on them are sometimes even bigger in that department.

[newlexman]

Can the differential have anything to do with my 91 ls 400 feeling like it needs motor mounts. My mechanic said the mounts are strong, but I feel to much shifting of the car when i put in reverse or go to drive. And when i am driving there is a delay in the shift, but I know it is nothing wrong with tranny?

[glenmore]

As wwest mentioned, most differentials have a vent. But I've never heard of one getting plugged. Also no crush washers, just a tapered plug.

glenmore

1990 LS400