Differential fluid debate: here it comes!

#1 02-06-2005, 12:17 AM

I'm going to be draining and refilling both the ATF and front diff fluid soon, and wanted to know everyone's opinion on which diff fluid to use. I've heard good things about synthetic, but everyone here seems to have something to say about the usage of synthetic fluids.

Any thoughts?

Landshark · #2 02-06-2005, 04:49 AM

i use Mobil 1, and the car hasn't puked it out yet.

pick your flavor.

svxfiles · #3 02-06-2005, 07:19 AM

I know an engineer, who builds very high quality "machine products"

, and he will only use Mobile 1 gear oil.
In fact, unless his customers use Mobile 1 gear oil he will not cover them under warranty.

michael · #4 02-06-2005, 08:44 AM

Mobile 1 in the diff and non-synthetic in the trans I didn't believe it until it happened to me. Synthetic trans fluid will leak out of the spots that organic won't. I have do doubts it functions well as a hydraulic fluid but I like my fluids in the car, not the driveway.

#5 02-06-2005, 01:00 PM

Quote:

Originally posted by michael
Mobile 1 in the diff and non-synthetic in the trans I didn't believe it until it happened to me. Synthetic trans fluid will leak out of the spots that organic won't. I have do doubts it functions well as a hydraulic fluid but I like my fluids in the car, not the driveway.

That's what I was thinking... Since the diff is essentially a sealed system, I think I may go for synthetic gear oil. But as for the trans, I'm sticking to organic.

What's the diff gear oil weight again? 80w90?

Beav · #6 02-06-2005, 01:27 PM

Yeah, but what if the synth leaks into the ATF?

(you know I couldn't let that go unsaid...)

#7 02-06-2005, 04:16 PM

Quote:

Originally posted by Beav
Yeah, but what if the synth leaks into the ATF?

(you know I couldn't let that go unsaid...)

If the differential fluid is leaking into the transmission, I think you've got some larger issues than synthetic-mixing-with-organic.

Beav · #8 02-06-2005, 08:03 PM

The point is that synth is more difficult to seal than straight mineral oil. The concern of possible external leaking isn't the only consideration. Just a thought...

#9 02-06-2005, 08:06 PM

Quote:

Originally posted by Beav
The point is that synth is more difficult to seal than straight mineral oil. The concern of possible external leaking isn't the only consideration. Just a thought...

What's your suggestion then, Beav?

#10 02-06-2005, 09:58 PM

I am currently using Mobil 1 in the tranny, diffs and the crankcase..no problems whatsoever..been using synthetics for years..and from experience and my humble opinion..if your car is leaking..it needs to be fixed

Beav · #11 02-07-2005, 11:06 AM

I really had no point to make, just tossing out considerations. I believe in synthetics but my experience is that seals not engineered for synthetics, especially those with more than a few miles on them, tend to have difficulty controlling synthetic oils. If you are concerned about external leaks when changing over you should be even more concerned about internal leaks.

#12 02-16-2005, 08:03 PM

Quote:

Originally posted by Beav
I really had no point to make, just tossing out considerations. I believe in synthetics but my experience is that seals not engineered for synthetics, especially those with more than a few miles on them, tend to have difficulty controlling synthetic oils. If you are concerned about external leaks when changing over you should be even more concerned about internal leaks.

I found a happy medium by using Valvoline DuraBlend 80w90.

Synthetic blends always seem to be a good idea to me.

I'm very glad that I changed to diff fluid today. I try to check it somewhat often, and it has always appeared to be in good condition. No bubbles/frothyness, and at the proper level. But when I took off the drain plug today, it had a nice dark brown color to it.

Not cool. I guess that's what we get for having a pure black dipstick to check it with... Once it turns a dark color, you can't tell!

And yes, that stuff does smell very foul. No matter what type or brand.

Chiketkd · #13 02-16-2005, 08:13 PM

Quote:

Originally posted by deruvian
I found a happy medium by using Valvoline DuraBlend 80w90. Synthetic blends always seem to be a good idea to me.

I use that exact same diff fluid in my front diff. The Durablend seems to be a happy medium for me as well...

-Chike

Jnthn_Sctt · #14 02-16-2005, 10:01 PM

Mobil 1 all around, Oil, Tranny, diffs. For the couple extra bucks it costs, it's cheap peace of mind.

dcarrb · #15 02-17-2005, 05:37 AM

Quote:

Originally posted by deruvian
I guess that's what we get for having a pure black dipstick to check it with... Once it turns a dark color, you can't tell!

That's where the "check twice" rule comes in: Pull the stick, wipe it on a white rag, reinsert it fully, and check again.

dcb