SpitfireS

I would not hesiate to use Amsoil SG 75W-110 in an OEM diff & stock power.

That said...

I am using Amsoil SG SAE 190 in my 4.57 diff.
The last diff oil change wasn't spotless in regard to iron on the drain plug, but I think I used it too long (29101km, 2 years including a track day)
This OCI will be around 15000 km / 6 months, still on SG SAE 190.

That said.....

If I had the choice, like 3 bottles on a shelf, LE 1605 / Amsoil SG 75W-110 / Mobil1 75W-90 I would still pick the LE as that is a single grade oil.
(in an OEM diff / stock power)

That said...

If you get low temps in the morning, the Amsoil would be best.

FISH22

Wow, lots of great info in here. Thanks guys!

If I were to go with the Amsoil... Is there going to be any harm done just dumping the LE, and filling with the SG? I know the LE stuff is some pretty thick/sticky stuff, so I'm sure there's going to be a lot left behind inside the pumpkin.

Would it be overkill to fill with SG, run for a few days, then do another empty and fill with SG?

FISH22

Oh, and my temps are really never that cold. Plus, the car is always in a garage that never sees below 50 degrees F.

INDYMAC

Here is the universal procedure for changing diffent gear oil brands:

1. Drain oil presently in the differential as completely as possible while the truck is still warm. This also helps remove contaminants and oxidized oil which can impair performance of LE gear lubricants. If contaminated oil remains in the differential, foaming can occur.
2. Do not use a volatile, chlorinated solvent or solvent-type flushing compound to wash out the differential. Any solvent trapped in the voids of the reservoir will cause corrosion. Also the presence of even a very little amount of solvent-type flushing compound will reduce the viscosity of a gear oil. Further, without a coating of oil for even a short time, rusting of internal parts of the differential can take place.
3. To properly flush the differential, use a light viscosity turbine oil or non-detergent engine oil (SAE 10 or 20). Jack up your truck (no-load condition) and run in gear for 15 minutes and drain. Note that some units can be so badly oxidized that physical removal from the inner surfaces may be required.
4. If new gears are installed make sure that the new gears that come with a rust preventative are cleaned off. This insures that any rust preventative, debris, metal chips and core sand is removed before installation.

INDYMAC

Yes, I'm a BITOGER too. Unfortunately, what we have here is what we have over there too. Lots of regurgitated hype and product data sheets. I'd like to see more real world data on both sites so we can all make more informed decisions. I know it costs $20-30 to do a test. And $100 or more to really get useful data. But I can only do my fair share of tests. It takes a long time for me to accumulate the mileage necessary to test, so I can only do one or two a year.

I'm a genuine LE user here in S.Texas. But for members living up north, I'd like to be able to recommend AMSOIL SVT 75W-110. I just have never seen any useful data or testing on it in any platform since it came out. That disappoints me.

Bror Jace

Agreed INDYMAC, more real world testing would be great. I assume you've seen the LE vs. Red Line gear oil tests from an S2000 ... or where those actually yours?

Anecdotal testimonials and scant UOAs are far from perfect but they are mostly what we have ... and as I said before, any of the stuff on the shelves will be OK if the duration isn't too long ... and it's the correct fluid (no CRV dual-pump nonsense).

As for flushing, I agree to avoid any solvents/cleaners. I would use a cheap oil, run it for 1,000-2,000 miles then drain and refill with the oil you intend to run for long-term use.

FISH22

Well, I just ended up ordering some LE 1605 from Ricks2k.com.

Thanks though for all the info guys.

INDYMAC

Yes, I posted that comparison a few years ago on BITOG. Unfortunately, most of those formula's are obsolete now. But it still might be useful for comparison of what wear rates these differentials are capable of shedding.

I prefer the mineral oil based gear oils, but I can understand the theory behind full synthetic gear oils being useful too. You will find that most of us here change the diff fluid probably more often than necessary (less than 10K miles usually). That's because our tranny fluids don't last very long (around 5K miles or less). For the DIY'er, most of us have assumed the following OCI's since lifting/jacking the vehicle presents a convenient opportunity:

Engine oil/filter change- 5K miles/or 1 year
Tranny fluid- 5K miles/or 1 year
Diff fluid- 10K miles/or 2 years
Brake and clutch fluid- 2-3 years

The diff only holds less than 1 quart, and we're asking it to do a lot of work for us. I think 10K miles is reasonable and conservative enough with either dino or synthetic.

INTJ

Plenty of good info in this thread. Bitog is a good source to start and there is a lot of interesting information, much provided from our s2k brethren.

Slip's link is very valuable. That is a very good example of how one oil outperforms another and then loses badly in the next test (GM for example), but if you just compare average trends you can see that the Redline and Amsoil do really well consistently, and RP does poorly. Some do a lot better after use, oxidation, and some fall out of grade almost immediately.

But, keep in mind as Bror and several other folks have mentioned, these and most things we read are press-releases. There are no error bars, and there is no identification as to what wear would be identifiable over 100k.

Also, the diff mechanism is very strong and very forgiving. You can run almost anything in there and the wear is not really noticeable.

When Audi first brought these out on the mass production scale on big fat cars with lots of torque they had the same results as the Formula SAE people with very high HP and no weight, perfect functioning for the life of the vehicle. The unit manufacturer has super broad lube specs.

That being said, ours holds less than a liter, so twice a year for no track cars is probably perfect with a good fluid. The first SCCA AX cars did get a lot of fine metal powder after a full season, and while the unit just compensates by sliding the gears slightly more, if you want the unit to last 100k, change it more frequently if competing.

I like the LE, but although it is supposedly a semi syth, I got distinct gear noise at 0 c, so save that for summer in most places. I run a full synth in the winter and the LE in the summer. Changing the fluid and not doing clutch dumps will let this unit last a very long time.

SpitfireS

INTJ Posted on Jul 25 2010, 05:13 PM
With the diff mechanism you're talking about the Torsen unit?
Torsen claims it can run on ATF (IIRC), but I've noticed a change in limited slip behaviour when the oil "gets old", when the oil can no longer deal with the forces generated by the gears inside the Torsen housing.
"Worn oil" made the car handle different, especially around low speed, on the throttle, tight corners, when the Torsen is working hard to devide the power to wheels that rotate at different speeds while having equal grip.
Changing oil reset the behaviour back to were it was - or where it should be.
With "worn oil" I mean: sheared base oil, depleted add-pack and in the case of multi-grade oils one adds: sheared viscosity index improvers.

The final drive gears certainly can not run on almost anything.

UOA's of diff oil are IMO more usefull than engine oil UOA's when it comes to actual wear as in our case you have the magnetic drain to complement the UOA findings and one can actually inspect the ring gear through the drain hole.
That is 2 things one can not do so easily when it comes to engine wear.
Low ppm of iron, not a lot of iron specs on the drain plug and a mirror finish on the ring gear after a reasonble amount of milage = good oil.
If low cost (20-30 Euro) UOA's were available overhere it would have been a now-brainer to send in a diff oil sample of SG SAE 190.
Unfortunately, they are not, last engine oil UOA's was 133 Euro.