JesLet

iTrader: (19)

So I have searched, that if my differential has that label that says 75W-90 synthetic only, then I should fill it up with that said weight.

Quote:

That depends on if your SC430 has the Synthethic Oil tag on the rear differential.

Info from 2004 SC430 Manual :
Oil capacity 1.35 L (1.42 qt., 1.19 lmp.qt.)

Oil type and viscosity

Vehicles without synthetic oil information label
Hypoid gear oil API GL-5
Above –18C (0F): SAE 90
Below –18C (0F): SAE 80W or SAE 80W-90

Vehicles with synthetic oil information label*
Toyota Genuine Differential Synthetic gear oil
API GL-5 SAE 75W-90 or its equivalent

*Vehicles with synthetic oil information label only:
The following label is affixed on the right side of the
differential carrier. Use the type and viscosity shown on
the label when the differential oil is replaced.

Problem is, I bought a used differential from a 2003 SC430 and there was a lot of rust and there's no label that says I should fill it up with 75W-90 synthetic.

My question is specifically, when did Toyota change it to synthetic? I believe 2004 and up now uses synthetic, but don't quote me on that.

So, anyone who has 2003 model, can you please tell me if it's synthetic 75W-90 or regular 80W-90?

bacardi11

iTrader: (1)

I have a 2002 and I use synthetic in my car. engine and differential.

texsexlex

iTrader: (3)

...I don't know for sure, but wanted to pose an additional question...why wouldn't the synthetic work in all of our differentials? If it was labeled synthetic only, then I would only put synthetic in it. But if regular gear oil was in it originally,then would switching it to synthetic cause any issues ???.I'm asking this,because alot of us have switched to synthetic motor oil in our cars. Wouldn't this be along the same lines of added protection (hopefully) ???

JesLet

iTrader: (19)

You have point. I have a 97 SC300 that only requires 80w-90, most of the SC300 guys uses sythethic 75w-90 and I am using that oil too.

When I switched to 3.92 gearing (SC400), I noticed that my 4.27 SC300 diff has a litlle noise when I turn the shaft... and this is when I am using 75w-90 oil on it. Now I have the 3.92 SC400 diff on it and using the same 75w-90, I hope it will not make the same noise when I take that one off and switch it to 2003 Sc430 diff.

This is the whole reason why I would like to know if I should use 80w-90 or synthetic 75w90.

bacardi11

iTrader: (1)

the ring and pin. may be out or was going bad. should have no sound.

kjcole

Yes, if howls slightly it's the pinion gear.

gripau1

Switching to full synthetic shouldn't cause any issue. In fact running a full synthetic will allow the gear oil to maintain its viscosity and not breakdown at higher temperatures compared to a non synthetic gear oil.

A diff oil is not expose to fuel (blow by), condensation,coolant and extreme heat compare to engine oil. That's why you change the gear oil at 80,000-100,000km intervals. You would only change the diff oil regularly if you race / drift the car as oil is cheap insurance compare to a new diff.
Also changing the diff oil removes the metal filings suspended in the oil or stuck to the magnet.

What kills the oil in a diff is heat and the extreme shearing effect of the gears on the oil.

Also the function of the diff oil is to remove heat away from the gears and transfer the heat to the walls of the diff.

Recommend to use 75w-90 diff oil for daily driver. Only if your diff is noisy I would go for a thicker 75w-140 gear oil. You can get up to SAE 190 - 250 gear oil for really extreme drag racing, circuit racing and drifting!!