Can ATF be used it the diff..?

[ladd220]

Hi all,

I have a 1996 e220 coupe and there is a slight howl coming from the diff. As a low cost treatment i have thought about changing the diff oil first to see if it makes a difference.

As this is my first MB, i asked a retailer for advice on which fluid to use...

His suggestion was: Titan Fuchs ATF 3000 Dexron II....

Is this right? can ATF be put in the diff?

 

[Sp!ke]

I think the diff oil is just plain old 80W90 gear oil.

When you do get around to doing the job, make sure you can undo the upper fill point hex*before* undoing the lower drain point hex. (dont ask )

 

[BlackC55]

Don't use atf in the diff 75W 90 or 80W90

 

[grober]

Some MERCEDES limited slip ASD DIFFERENTIALS run a type of hydraulic fluid similar to ATF but otherwise they run a pretty standard hypoid GL5 gear oil.

Hypoid" is not really a question of oil, so much as a question of gearcutting. Old (1920's) rear axles used straight bevel gears to form the crownwheel and pinion. These had two disadvantage, the pinion shaft meets the crownwheel on its central axis, and the straight cut gears are noisy. By using a more complex "hypoid" gear tooth shape (if you look at a pinion, the teeth appear twisted) these problems can be addressed. The more gradual engagement of the teeth along their length reduces noise. By careful design of the geometry the pinion can be made to mesh _below_ the axis of the crownwheel. As the centre height of the crownwheel is fixed by the wheel height, this allows the propshaft to be lowered relative to the car body, giving a clearer floorpan and lower centre of gravity for better cornering. Hypoid bevels are now universal in this application. Because of the sliding contact that hypoid gears make, their hydrodynamic contact pressure is higher. To be suitable for use with hypoid gears, a lubricant must be capable of resisting high pressures. Oils with "EP" ratings (Extreme Pressure) such as EP90 are required. Some brands describe themselves as "hypoid" instead, a term which is synonymous with EP. They often contain sulphur-phosphorus additives which can cause them to smell strange.

API GL-5: Clearing up the Confusion - Automotive Gear Oil Additives - Driveline Additives - The Lubrizol Corporation

 

[ladd220]

Graeme, Olly, Sp!ke, thanks for your replies...!! - It has made my choice alot clearer.

Also, can changing the diff oil make a noticeable difference to the MPG..?

 

[grober]

Graeme, Olly, Sp!ke, thanks for your replies...!! - It has made my choice alot clearer.

Also, can changing the diff oil make a noticeable difference to the MPG..?

Sadly no! Mercedes diffs can howl slightly especially on the overrun and can go on for many thousands of miles this way- just keep the oil topped up to the correct level.
ps they also tend to leak a bit out the front diff seal- tends to look worse than it is

 

[ladd220]

Ah well.... as long as the howl is gone i'll be happy...!

And sp!ke, I have taken on board your suggestion on opening the fill plug first, I've read about not being able to open it after the diff has been drained.!

I'll get this job done on the weekend and let you know how i get on. Thanks.!

 

[ladd220]

cheers graeme, that also answers the question as to why there was a single drop at the front of the diff.