tdbrown75

I’ve had gear issues. In fact I’m on my 3rd set of 4.10s. I nearly sold the car at one point it was so frustrating. My car was in the shop over 8 weeks total over a four month period trying to get my issues straightened out. I finally had success and a perfectly quiet set of 4.10s, until yesterday.

How did they get quiet finally? Well Ford did a warranty replacement on the entire axle housing, and in went a brand new set of 4.10s with races, bearings, cups, etc. To make a long story short I have 1000 miles on the rear and I’ve been breaking in this whole time, not leaving anything to chance. Just for that last piece of mind I decided to go ahead and switch out the factory “break in” fluid (regular Motorcraft stuff) with Royal Purple. Lord knows I don’t need any more issues with the rear of this car.

So I pull out on the highway and immediately notice a faint whirr. My stock gears did that, no biggie I could barely hear it but definitely not there before the fluid change. As I’m driving home I notice whine on deceleration! There was none before the fluid change, zip, zero zilch! I had the quietest set of gears I had ever heard including stock, until the Royal Purple went in. Nothing else was mucked with during the change; the mechanic took his time, cleaned it up real well and filled it up good. I used the 75w 140 stuff and no friction modifier (and I have no clutch pack noise).

So Aside from feeling like I wasted good money I’m now left wondering if I should leave this stuff in there or waste more good money going back. I know some will say maybe they were not right in the first place, and maybe that’s true, but they are right enough that they are silent with stock fluid. It’s a faint whine in a narrow range so I’ll probably just leave it be. It just chaps my ****!

Anyone else have a similar experience, and what’s your opinion on leaving this stuff in?

Tim

howarmat

why did you leave out the friction modifier? i would have put it in even though RP says you dont need to

tdbrown75

I know lack of friction modifier will cause clutch pack chatter (binding), but you sure it can lead to gear whine and whirring sounds too?

Tim

Norse1974

Never had any issues with RP at all. Actually its the name brand I pefer to use through out my entire driveline. Its hard for a company to be 100% perfect. Theres always gonna be a guy with a horror story about any manufactuer you can think of including the guy on here who just bought a 2011 5.0 & it caught fire while driving! How you think he feels about Ford now???? I would switch it back to how you had it & see if RP is the real culprit. If the noise stops after going back to the old fluid then ya know for sure.

moosestang

coincidence. I would also put in a bottle of friction modifier.

Unleashedbeast

I'm not so sure it's the fault of Royal Purple's formulation. It's possible that the tech who worked on your car used a very heavy "shock" gear oil in your car, something in the 190 to 250 weight range. The extra viscosity is known to quiet gears, and since they were having trouble getting your rear end quiet, they used a known remedy. When you used Royal Purple, it's only 140 weight, and will allow for more gear noise.

I bet if you use the fluid linked below, your noise will disappear again.

Amsoil 190W gear oil

or

Red Line Shock proof gear oil

SON OF 68

That's kinda weird. I would bet that unleased is pretty accurate saying they probably had a heavier fluid in it to keep it quiet. I have 3.73 Ford Parts in mine with RP. It was done by Deans Performance and is as quiet as could be. I would try a heavier fluid and see if the noise stops. Be nice to know what the shop used when they installed it. That might answer a lot of questions for you.

SamsBlueGT

Royal Purple Max-Gear Oil does not need additives.

Unleashedbeast

Don't believe everything you read. I've tested their fluid, and like other top tier gear oils, required extra friction modifier to quiet the clutches.

SamsBlueGT

I have been known to be wrong before in my life... I put that gear oil in mine and haven't noticed any extra noise yet though.