Using synthetic gear oil??

[Tornado]

Hello,
If you switch to a synthetic gear oil, are you stuck with always having to use it? Or can you switch back? I recently went with a synthetic up front and out back, (Valvoline 75-90 GL-5) and now I notice a slight hummm while coasting at a lower speed around right hand corners. I also added 2 bottles of the BG LS II additive. The dealer is keeping it for a few things, and their going to check on it, but I thought I'd run it through you guy's (and gals)

Any thoughts would be greatly appreciated!

[psychos2]

you can switch back without a problem.i don't think anyone has had problems with synthetic gear lube.i have synthetic with 1 lsd additive added and no problems. shawn

[VCrossfan]

I use.. Royal Purple Max Gear..75w140...front/rear...no additive needed. No problems. Look on ebay for a seller named "racer17k" (Karl Racing Royal Purple oil) is his store name. Price was right and fast shipping. He also had the ATF oil...

[Joe_Black]

Most synthetics are fully compatible, so you can go back and forth or even blend. As for the hum, since it's audible during a coasting turn, it could very well be gear noise. When you're decelerating the wheels often turn the driveline, which means the back-side of the gear faces get engaged. Since they're not worn in like the the other, normally driven side it'll make noise like a fresh gear set.

This is just an idea based on experience, so I can't say for sure without hearing yours in person. But it's something to think about.

[Andrey]

I use Royal Purple everywhere but engine - very satisfied (should've done that day one !) Drive is much smoother adn lower in noise and humm..

[Kahuna]

I use Mobil 1 with NO problems.

[DK]

I use Royal Purple everywhere but engine - very satisfied (should've done that day one !) Drive is much smoother adn lower in noise and humm..

A friend who drives Porsche and Ferrari was waxing enthusiastic about syn oil for the engine the other day. Says he uses it in all his cars. I'm curious. Why don't you use it in the engine?