DIY F85/86 Differential Fluid Change

[SaNGRia]

Hey guys i have purchased the fluids and waiting them to arrive. I got 75w90 for the front and rear also 75w140 for the outer part. I am still trying to figure what is the difference between 75w85 carbon vs 75w140 other than viscosity. What carbon adds to that oil and makes it so special? I just wanna find out the purpose of the carbon feature. I dont mind to order 75w85 carbon if it helps something special in the unit!

Here is additional information :





Additionally i got 75W90 for the front diff as shown on real oem

[640ijims]

I believe the carbon in suspension acts as another form of lubricant…sort of like the stuff we used to squirt into home door locks when they got sticky. This was a powder in a squeeze tube…graphite I believe.

[///MCollection]

Not sure but would imagine as said above it's additional lubrication

[SaNGRia]

I have talked to ECS before items shipped out. They said you can use 75w140 since it is Limited Slip. I will just use it. If i have any issue i will swap to OEM.

[Yuille36]

I used 75W-140 in the entire diff. Although this is supposed to use on the left/right side only where the clutch packs are located. 75W-90 is supposed to be used in the center for the ring & pinion. But the forum ridiculed me for doing so, but after months and many miles, I haven't experienced any issues. At the end of the day the major differences between the two, is one has an friction additive added. So should you be worried.....no not in the slightest.

[///MCollection]

I believe it was me who tried to help by saying it was the wrong fluid and level and wasn't aware I ridiculed you, I for my own vehicle would rather use the correct specification and amount and uploaded for everyone's benefit the correct instructions. We all make our choices and except any consequences but I wasn't aware of ridicule just information.

[SaNGRia]

Originally Posted by Yuille36

I used 75W-140 in the entire diff. Although this is supposed to use on the left/right side only where the clutch packs are located. 75W-90 is supposed to be used in the center for the ring & pinion. But the forum ridiculed me for doing so, but after months and many miles, I haven't experienced any issues. At the end of the day the major differences between the two, is one has an friction additive added. So should you be worried.....no not in the slightest.

So the 75w140 doesnt have friction but the carbon does? Well friction additive was the one causing issue on e9x m3 diffs. If i am not mistaken it was making noise on turns. How many miles you are with the 75w140 ?

[///MCollection]

I'm pretty sure the friction modifier was added to the e46 m3 diff to stop the noises on tight turns so it must be a slip additive thinking about it. unsure about the e9x.

[SaNGRia]

Castrol SAF-XJ PRODUCT DESCRIPTION

Castrol SAF-XJ is a full synthetic SAE 75W-140 final drive lubricant. Formulated with an optimal
combination of frictional characteristics and viscosity profile, Castrol SAF-XJ has been developed
to help overcome noise and “stick-slip” problems in limited slip differentials in a variety of different
vehicles. Castrol SAF-XJ has excellent high temperature performance providing exceptional
wear.

PRODUCT APPLICATION

Castrol SAF-XJ provides protection under high load and high temperature conditions. The
superior cold flow properties of Castrol SAF-XJ allow for improved gear and bearing protection at
start up, reduced torque loss and increased driveline efficiency. Castrol SAF-XJ has the ability to
reduce final drive temperatures through reduced friction, contributing to extended oil and
component life.
Castrol SAF-XJ can be recommended for most passenger car and light commercial vehicle final
drives with or without limited slip differentials, where API GL5 lubricants are required. Castrol
SAF-XJ is approved by BMW for use in rear axles fitted with limited slip differentials. It should not
be used in BMW rear axles without limited slip differentials. For these applications please refer to
Castrol SAF-XO

PRODUCT FEATURES & BENEFITS

Features

• Optimal combination of frictional characteristics and viscosity profile for excellent noise
reduction, helping to avoid “stick slip” and improve differential performance.
• Excellent antiwear properties over all temperature and load conditions for better final
drive protection and enhanced component life.
• Excellent cold flow properties for improved gear and bearing protection at start up,
reduced torque loss and increasing drive line efficiency.
• Excellent high temperature performance due to wide span viscosity for better start
protection under high load/high temperature conditions.

Benefits
.
• Shear stable viscosity for constant viscosity and performance during oil life
• Good anti-pitting behaviour helps to protect components, extending driveline life.
• Advanced synthetic and antioxidant formulation for good oxidative and thermal stability,
providing enhanced component cleanliness and extended lubricant life.

PERFORMANCE LEVELS
• SAE 75W-140
• ZF TE-ML 05D, 12D, 16G
• BMW approval for rear axles with a limited slip differential

Satisfying.

[///MCollection]

Good explanation, well found!

[Yuille36]

Originally Posted by SaNGRia

So the 75w140 doesnt have friction but the carbon does? Well friction additive was the one causing issue on e9x m3 diffs. If i am not mistaken it was making noise on turns. How many miles you are with the 75w140 ?

I have 8K on the driveline, since I last changed the fluids. And zero issues, if anyone was interested.

[SaNGRia]

Originally Posted by Yuille36

I have 8K on the driveline, since I last changed the fluids. And zero issues, if anyone was interested.

Appreciated. Will use the 75w140 on outer part.

[SaNGRia]

Originally Posted by ///MCollection

Good explanation, well found!

Yeah. I just wanted to make sure it meets all required oil tech. Seems like similar to Carbon. I also found this product which has been used on GM vehicles. And if you read the description it says Specially recommended for ZF limited slip differentials with carbon linings. So this must be the same thing without BMW logo on it!

[nishfish87]

And here I put the non friction modifier redline fluid in my E92 M3 with no issues for over 30k miles and probably 3-4yrs.

I'd say it's easy to keep it safe and use the modifier in the F85, no point in making this more complicated than it should be.

[SaNGRia]

The point of the discussion is to find most compatible product and done with it. When i am done with the DIY and share here, i want no one to look bunch of different options while the one will work without an issue. I am glad everyone has some good input.

[Yuille36]

The one denominator is that you change your fluids. What fluids you use, is your personal choice, but change the fluids.

[Klienfeld303]

Originally Posted by Yuille36

The one denominator is that you change your fluids. What fluids you use, is your personal choice, but change the fluids.

Hai Guize! Does your rear differential "sweat"? I changed my transmission fluids at my local shop and they noticed my rear differential was leaking a bit. I had them leave that section of the fluid change out so I can have the dealer evaluate the differential. According to habberstad bmw the differential is supposed to sweat a bit. Still curious if that's true or should I check my seals and then replace with fresh fluid.

What's your thoughts?

[Yuille36]

Originally Posted by Klienfeld303

Hai Guize! Does your rear differential "sweat"? I changed my transmission fluids at my local shop and they noticed my rear differential was leaking a bit. I had them leave that section of the fluid change out so I can have the dealer evaluate the differential. According to habberstad bmw the differential is supposed to sweat a bit. Still curious if that's true or should I check my seals and then replace with fresh fluid.

What's your thoughts?

I have never heard anything like this. The rear differential is supposed to sweat, this is BS. My diff is as dry as the day it left the assembly line.

[Klienfeld303]

Originally Posted by Yuille36

I have never heard anything like this. The rear differential is supposed to sweat, this is BS. My diff is as dry as the day it left the assembly line.

Exactly my thoughts. I'm going to take her to my mechanic to have it thoroughly inspected.

[Viper501]

Sounds like old Porsche joke that if it’s not leaking oil it’s empty. Definitely BS.

[bmwx5er]

Newtis warns not to change oil in the left and right chambers, and only to do it in the middle chamber.

[Yuille36]

Originally Posted by bmwx5er

Newtis warns not to change oil in the left and right chambers, and only to do it in the middle chamber.

I change my oil in the center where the ring and pinion are housed as well the left and right sides. This was 8000 miles ago, without any issues.

Why do people fear changing their fluids in their vehicles. Forget what BMW is telling you and change the dam fluids, or don't. It's your choice.