C107 450SLC limited-slip diff oil specification - is it 75W90 GL5 or something specific

29-11-2024 02:18 PM

#1

Banksia_Park_Berny ★ Silver - Unaffiliated

★ Silver

Join Date: Sep 2008
Location: Banksia Park NSW
Posts: 1,847
Club: M.A.L.A.K.A.S.
Car: 1985 W126 380SEL

ok question.

1978 450SLC due for a diff oil change. The diff is a limited-slip (LSD). The handbook in the glovebox is reproduction (not original Mercedes) and just says "75W-90 GL-5" with no further detail.

R107 and C107 rear differential service reference

I know LSDs of this era need a friction modifier additive or the clutch packs chatter. Is modern 75W-90 GL-5 sufficient on its own or do i need to add a friction modifier seperately. What brand are the boys using.

29-11-2024 03:48 PM

#2

Vasilios_Billy

Lifetime Benzer

Join Date: Mar 2008
Location: Campbelltown NSW
Posts: 1,864
Club: M.A.L.A.K.A.S.
Car: 2020 AMG GT C

Berny.

The original specification for the W126 / C107 / W116 limited-slip differential is API GL-5 / SAE 75W-90 with the Mercedes-Benz approval 235.0 for LSD-equipped vehicles.

235.0-approved oils contain the friction modifier package as supplied. You do not need a separate additive if the oil is 235.0 approved. Examples of currently-approved oils (2019):

Castrol Syntrax Limited Slip 75W-90 - 235.0 approved, $28 per litre at Repco
Liqui Moly Top Tec MTF LS 75W-90 - 235.0 approved, $38 per litre at MB specialist
Mercedes-Benz Genuine LSD oil (under A 001 989 23 03 13) - 235.0 specification, $65 per litre

The C107 diff holds about 1.3 litres so you need 2 litres allowing for spillage.

Do not use a non-235.0 oil and add separate friction modifier (e.g., GM-spec or Ford-spec modifier). The Mercedes-spec friction modifier package is calibrated for the specific clutch-pack material of the Mercedes LSD. Mismatched modifier results in clutch chatter under heavy load.

29-11-2024 06:18 PM

#3

Banksia_Park_Berny ★ Silver - Unaffiliated

★ Silver

Join Date: Sep 2008
Location: Banksia Park NSW
Posts: 1,847
Club: M.A.L.A.K.A.S.
Car: 1985 W126 380SEL

Vasilios cheers. Will grab the Castrol from Repco this week.