plAythiNG

I have heard from a reputable diff specialist that the 4.77 FD should use a thinner diff fluid due to the backlash required.

I an going to be running OS Giken LSD, and thus looked at the OS Giken diff fluid which has a 250 weight. He reccomended I look at 90 weight, or even 140 as it is thinner, and with the 4.77 final drive, since it has a smaller backlash requirement, will flow better with the thinner fluid..


Thoughts?

RedCelica

140 is not thinner than 90, it's heavier. higher # = heavier weight (ie: thicker; ie: higher viscosity) btw. OS Giken recommends 80w-250 in their diffs, and make their own fluid especially formulated for them: http://www.turnermotorsport.com/p-18...0-1-liter.aspx

Cold oil is thinner (less viscous) than hot oil also, and this is to allow oil to flow more easily until the engine reaches nominal operating temps, which heat the oil and make it thicker.

Sylvan

I'm pretty sure you have this last paragraph backwards. I don't know of any oils that get thicker as they warm up. Look up oil viscosity vs. temperature and you'll see many charts showing viscosity decreasing as temperature increases.

plAythiNG

sorry looks liek my post was viewed in the wrong light. I understand that the higher the number, the thicker/heavier the oil is. When I said "which is thinner" this was in relation to OS Giken's fluid weight of 250.

I think a big reason for me going with 140weight over 250weight is the fact that I am running the spoon diff casing which triples the volume of fluid contrary to the oem casing.

Just wanted to get some constructive feedback etc.

windhund116

OS Giken Synthetic lube is 80W-250. So, it should flow like an 80W oil, at ambient temps. But at race temps, will be at 200W. Since you are using Giken LSD parts --- I'd go with their oil, as recommended. As says it works well under typical daily driving conditions AND their LSD parts are designed to run in their 80W-250.

Just my 1¢ worth of 2¢ .


From Giken site:

OS-250R Full Synthetic Gear Oil

The OS-250R was specifically formulated to provide maximum performance and smooth comfort for the OS Giken Super Lock LSD. SAE Rated at 80w-250, it is the top choice by race teams for protection and durability, yet maintains street-driveability. (Not recommended for transaxle applications.)

plAythiNG

makes sense RE the flow at colder temps.

I also emailed a bunch of OS GIKEN distributors around the globe. So far I have just received one response from the USA guys. Such that you guys are aware of what I advised each of these guys. My email:

Hi Team,

Greetings from Australia.

I own a Honda S2000 track orientated car. The car primarily sees use at the circuit, however being street registered I do drive the car on the street from time to time.

The purpose of this email is to gain feedback on what diff oil to use.

I am currently rebuilding my diff with the addition of the following modifications:

• Higher ratio final drive. OEM is 4.1. I am upgrading to 4.77
• Spoon enlarged diff casing. Increases fluid capacity from 800ml to 2300ml (almost triple)
• Shot peening & ISF treating everything
• Will be running a small 4 row diff cooler with manual switch as I am going to run a defi oil temp sensor to monitor temps, and when in the red will flick switch to run pump to cool oil
• OS Giken LSD

Now I have read a lot of posts online, as well as you guys recommending the OS Giken in house diff oil. This is 250weight. Now oem is currently 90weight, and a lot of S2000 track enthusiasts like to run the 90 or 140weight. Now I am happy to run the OS Giken fluid however it’s weight does concern me. Being 250weight, its quite thick, and am concerned that whenever I street drive the car, I might be waiting a little too long than my patience can handle to wait for the diff to get up to some decent temp to actually roll off and slowly drive the car etc. As mentioned I will be running the Spoon diff which triples the volume of fluid I’d be running, PLUS the diff cooler which may see another quart of oil being used to fill the diff. Since the OS Giken fluid is quite thick/heavy, plus running at least three times OEM capacity, I am not sure if I should be running the OS Giken fluid, and a 140weight might be more suitable to my diff build.

Looking forward to hearing from you.

Regards,
Alex

The response is:

Hi Alex,

As you are running a differential cooler, we recommend you use the Motul 75W-140 gear oil.
You can also run OS-250R, but we advise to not activate your differential cooler until the oil is well up to temperature.

Best Regards,

Sean F

windhund116

Alex, if you are going to track this car a lot --- using that OS Giken LSD diff --- use the Giken 80W-250. The idea of higher viscosity rating is prolly to maintain adequate lubrication at race temps. Diffs need this, or you risk early failure. The Giken unit must produce a lot of heat in racing conditions and needs that special and prolly $$$ lube.

It really doesn't make sense that Giken would go to the trouble of having that oil specially made for their LSD diff. Then, the end-user using some other weight oil. After the cost of having that unit put into your car, use their oil. And check and change as needed to prevent early wear.

Good luck with that! Seems like a very nice diff...

plAythiNG

I'm going to run this first: Motul Gear Competition 75W140 Diff Transmission Gear Oil

Espeically in the break-in period.

After 2000km on street driving and figure 8's, i'll drop the fluid, and use the Motul again...

Since I have an oil temp sensor, i'll monitor temps and check for noise etc. if nothing else bad, i'll enter a track day, and see how I go.....


Just worried using that thick OS Giken oil given that I will have over three times the capacity too!

Emil St-Hilaire

LE 1605.