Rear Diff fluids

[TestMe]

I just had 4.10 frpp gears and and a limited slip diff installed. the mechanic said to use regular fluid over synthetic which it already had. he said it would slip if i used synthetic. is this true and what other maintenance do i need to pull on it?

 

[NastyStang113]

I've always used synthetic oil in my LSDs with zero problems, even during break in. I'd do the heat cycles like advised and than change the oil to a synthetic like Royal Purple after 500 miles. Most people are surprised at all of the metal shavings that are removed after a new set of gears are installed and they complete their wear pattern.

 

[gmantheman]

A trusted shop here in San Diego that only does gears, and things of that nature recommends using a quality petroleum based gear oil vice synthetic. They use Schaeffers oil. I had them change my gear oil. When they changed my oil, there were no metal shavings. Here is a link: tech tips

 

[NastyStang113]

A trusted shop here in San Diego that only does gears, and things of that nature recommends using a quality petroleum based gear oil vice synthetic. They use Schaeffers oil. I had them change my gear oil. When they changed my oil, there were no metal shavings. Here is a link: tech tips

Do you have a magnetic drain plug or dip stick? If not, it's very hard to see metal shavings from the gears creating their wear pattern which is normal. I've never seen a set of gears that didn't do it.

 

[kenaimone]

Dave at MMP (ck pg 66 of MMFF Feb editon) installed my gears 10,000mi ago and used royal purple 75W-140 and the Ford friction modifier during the install. i changed the fluid at 500mi, and never had a problem.

 

[NastyStang113]

Dave at MMP (ck pg 66 of MMFF Feb editon) installed my gears 10,000mi ago and used royal purple 75W-140 and the Ford friction modifier during the install. i changed the fluid at 500mi, and never had a problem.

I think they've got a Royal Purple that doesn't require the friction modifier, it's already got it in the blend. It'll save you some money next time you have to change the differential oil. The friction modifier is pretty expensive, especially OEM Ford fluid.

 

[kenaimone]

it is pretty cheap. it think i paid six bucks from a local ford dealer. i will pay that all day for a little insurance. i look at it like this, ford has the money (for a little bit longer anyway) to hire guys who know what they are doing. i will take the engineer from ford and add him to the guy that works for royal purple , and make the best of it.

 

[NastyStang113]

It's your car, do what you want ..

Royal Purple Gear Oil

Max-Gear is an ultra-tough automotive gear oil. It’s designed to maximize power and provide unsurpassed protection to heavily loaded gears. It makes gears run smoother, quieter, cooler and longer without overhauls.

Max-Gear outperforms other gear oils because it combines the highest quality synthetic oils with Royal Purple’s proprietary Synslide additive technology.

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. 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.

 

[gmantheman]

Do you have a magnetic drain plug or dip stick? If not, it's very hard to see metal shavings from the gears creating their wear pattern which is normal. I've never seen a set of gears that didn't do it.

I didn't have either. I asked the guy when he was changing the diff fluid. He said he didn't see any metal shavings.