I have a word for you, condensation,at the minimum. I would replace the oil, and be done with it. Been than again, the world may be flat yet.

 

What people don't understand is letting your sit around is bad for it. Seals harden ,condensation and corrosion set it and fluids like to be cycled.

 

I have always wondered where this "condensation" comes from, given that the differential is sealed.

My FSM says on page 0B-3: "The manual transmission or transaxle fluid does not require changing".

I also don't understand why this is so complicated. If you think the oil should be changed then do it. If not, then don't.

 

Ever see a "sealed" jar, water bottle, etc with condensation on the inside? There is moisture in the air, virtually everywhere. It's called "humidity". When you "seal up" your rear diff, there is air inside it, that came from the air outside it...that has moisture in it. When you change the temp of the diff, that moisture can condense on the metal parts the parts can then corrode...especially if the car has sat (a lot like in the OP's case), and the metal parts aren't evenly coated with oil. Corrosion puts gritty particulate in the oil. The oil becomes an abrasive. The parts wear. Can you see it now? This is one potential issue. I feel that there are others, and $10 worth of oil is worth the piece of mind, for me.

I don't know that sitting for years qualifies as "normal use". Also, car is engineered to last 100,000 miles...and many (most) are over that. So what to do??? The recommendation of THIS mechanic is to spend a few dollars and change the oil. Take a sample if you absolutely feel the need to know for sure.

 

The reason I asked about condensation is that the volume of air in a differential is pretty small. I can't imagine there's much moisture in there.

I guess we should be shooting some nitrogen in there when we change the oil, huh? Back in the old days when I was doing darkroom work I heard about an aerosol can that had nitrogen in it that you could spray into your chemical bottles to displace the oxygen and prevent oxidation. I assume that stuff is still available. I don't remember the brand.

I guess dry air from a compressor would work.

 

The problem with your theory is that the differential is not sealed, it is vented to atmosphere.

 

Arent you an IT? What ASE are you, if you dont mind proving via copy of your cert.

 

...

 

Yeah...That'll help prove you were right all along!

 

I'm both, why do you need proof are you hiring?

 

Not worth it.

 

Not worth the response. PM you.

 

unsubscribing.

 

The vent proves I was totally wrong about the condensation. Sorry for the distraction.

My car has 111K on it and the differential oil has not been changed since 1986 when I had a leak repaired. I'm planning on putting in a drain plug in the near future.

 

Don't know if anyone else does this but when I change my gear oil I just tip the car on it's side till it's empty.

 

Or if you flip it upside down, the oil will flow out the vent hole and you won't even have to remove the filler plug.

 

It's not something many people think about. I know I've seen them before than thought "WTF". I've never found out for sure, but I assume the fluid can (significantly) expand on a long trip where it builds heat. And, if the pressure were allowed to build, you might be more apt to blow out seals (like pinion or axle bearing).

Again, not the expert, just a guess. If wrong, I'd be interested to know the real reason.

 

This is absolutely beyond absurdity at this point. What are you trying to prove Kracken? Nobody said that having the oil analyzed was a bad idea, but here's the deal. If you have to crawl under the car, draw out a sample, then pay $25+ to send it off and have it analyzed, wait weeks for the results, only to determine what?

1. Yeah, it's fine, but now it's low on fluid because of what you sucked out so you're gonna have to buy new fluid anyway to top it off.

OR

2. It needs to be changed, which will cost little more than the analysis did in the first place.

It's a great THEORY if you're running a fleet of vehicles that you're putting a ton of miles on and you need to save every penny. But, he doesn't have fleet of Corvettes, he has ONE. Why spend $25+ dollars HOPING that your oil will be good enough to continue to use when you could just spend $35 and change it and then you KNOW.

You seriously don't want to get into a "credentials" pissing match around here, I promise you you'll lose. When you've driven your car as many miles going forward as most of us have in reverse then we'll be happy to listen to your input.

But then again, I'm an IT guy, I CAN'T know ANYTHING about cars. I guess that CDL driver's license just jumped in my wallet too.

 

Nathan, you could not have said it better. I find the C4 section to be the most informative of the entire Forum and it's because of a bunch of guys who don't mind sharing their knowledge and expertise with guys like me that are not as skilled or knowledgeable. It's not difficult to sort out the guys who've been there, done that and have the expertise, certified or not versus the relatively smaller group that feels the need to provide an opposing opinion just because they want some air time or need to get their post count up. I'm by and large a lurker that enjoys this forum and don't usually make comment. It' because of the knowledgeable guys here that I tackle small jobs on my C4 that I otherwise would be intimidated by. To you real experts who have walked that mile and have the expertise please don't desert us.

 

Hawk:

I have the "kit" the Ackman shows on his link. I bought it before my lift was install. While rebuilding the rear end (bushings) I just drilled and tapped it on the bench. But I did 1/2" NPT. It's just sitting around collecting dust. Never used. Sooooooo............. you can have it for just the shipping. Just send it on free to the next guy. Share the wealth. Let me know.

Dave