Oh,Oh,, Am I in trouble?

[EB-Z]

I'm in Toronto, Canada this week teaching a class on diesel engine mechanics. It's been hell since my training aids are stuck in customs and I'm free-wheeling without any material. I boot up my computer on a 10 foot overhead screen and there she is, the Z parked at the beach. Great way to get the conversation started with a bunch of strangers. So, we're having lunch today and one of the students at the table starts talking about the smell of gear oil on heavy equipment. I tell the story that happened to me about a month ago, where I change all my fluids over to synthetics. It's real hot outside, so I pull into the garage and shut the door (I have a window a/c unit in there) and proceed to do the brakes, engine, transmission and finally the rear end. Wow, that rear end oil really stinks! I tell them that my wife comes out of the house about 20 minutes later raising hell! Turns out the house A/C unit is in the garage too, and it sent all that AA (Auto Aroma) throughout all the vents in the house!
Anyway, to the point of this thread....
After the laughter dies down at the table, this mechanic asks if I added the additive to the gear oil to keep the rear end from burning up . I told him that I put in Mobil 1 and thought that you didn't need any additives with the synthetics. He thinks I need the additives no matter what oil I used and seemed pretty knowledgable about rear ends...Now I'm worried as I have put at least a thousand miles on her since changing the fluids.... Does anyone have any experience about additives in the gear box???? Am I tearing it up without an additive??
Please confirm that the student is just that,,,A student!!! and still needs to learn more about gear boxes in cars

Please, no laughing at me until AFTER I get consoled that my gear box is going to be just Fine!

Regards
Chuck.

[Rich Z]

It is my understanding that all limited slip differentials need to have a friction modifier added when the fluid is changed.

I found this quote that may be of interest:

Another important consideration when it comes to differential gear oil is the requirements of the limited slip, or traction-sensing differential. In a normal or "open" differential, the torque, or twist, created by the driveline is always applied to both wheels, regardless if one of those wheels happens to be spinning helplessly on an icy surface. A limited slip differential, or LSD, will sense this loss of energy and redirect torque to the wheel that has the most traction.

While there are various types of mechanisms used to accomplish this miracle of redirected traction, most of them require friction modifiers unique to their own design to work correctly. An LSD without these special lubricants will at best not work correctly, and at worst fail outright—ending up costing a bundle to rebuild and repair. If your vehicle has an LSD always be sure to use gear oil that contains the correct friction modifiers for that particular LSD.

Good luck!

[buckeyejack]

I would be inclined to believe that statement. Each manufactor uses different clutch packs in their LSD rear-ends. My old Trans Am would shutter and make noise until I added the right additive.

[EB-Z]

Some guys on "another" forum did some research and it turns out the the MOBIL 1 Synthetic Gear Oil already has friction modifiers in it........Just for future reference..

Whewwww.....



Chuck.

[Melsy]

As far as GM cars are concerned you need to add a small bottle of friction modifier when you change the rear end fluid-EXCEPT- if you use AmsOil. I recently changed mine on my '03 Z06 with AmsOil and no modifier and it works fine. In the early year's, 50's, 60's the modifier was made out of whale oil. Now it is obviously synthetic "whale oil". In the AmsOil literature they mention that the modifier is part of the fluid but you still might need to add another 4 oz. bottle if the clutches chatter. Mine works fine without it and it is my daily driver. Hope this helps.

[exile]

My understanding is that RP, Amsoil, and the latest Mobil1 all have modifiers that make it unnecessary to add to these gear oils. I changed to RP in November and have not had any problems.

http://www.royalpurple.com/prodsa/mgeara.html

Max-Gear is recommended for use in truck, motor home / RV, and automotive front or rear differentials, manual transmissions and lower gear units of marine engines that specify use of an API GL-5 or GL-4 fluid.

Max-Gear is an ultra-tough, high performance, GL-5 automotive gear oil designed to provide maximum protection to heavily loaded gears while maximizing power output throughout the drive train. It outperforms other GL-5 gear oils because it combines the highest quality synthetic oils with Royal Purple's proprietary Synslide additive technology.

Max-Gear makes gears run smoother, quieter, cooler and longer without overhauls.


All viscosities of Max-Gear are formulated with hypoid friction modifiers necessary for use in clutch or cone type differentials. No additional additives are necessary.