W115 FLUID CHOICE

[racing3000]

Hello. My car is 1974 w115 230.4 manual transmission. I will change the transmission and differential oil. The car manual says ATF II for transmission and hypoid SAE 90 gear oil for differential. However, some friends recommend hypoid 90 gear oil for the transmission and hypoid 140 gear oil for the differential. I got confused and would like to ask you. Thanks in advance for any experience or recommendation.

[Stretch]

Originally Posted by racing3000

Hello. My car is 1974 w115 230.4 manual transmission. I will change the transmission and differential oil. The car manual says ATF II for transmission and hypoid SAE 90 gear oil for differential. However, some friends recommend hypoid 90 gear oil for the transmission and hypoid 140 gear oil for the differential. I got confused and would like to ask you. Thanks in advance for any experience or recommendation.

Most changes from the authorised fluid in a Mercedes manual transmission / gearbox ends in problems - these gearboxes shift best with the ATF


As for the differential - changing to a heavier weight sometimes reduces noise they might be making. I'd stick with what the book says in most cases though (especially if you live in a cold climate)

[racing3000]

Thanks a lot. I always thought that how can another fluid type be suitable not declared in the manual officially. So, I am thinking in the right way about the transmission. Probably I will prefer Mobil ATF 220. After an extensive research, I released that ATF Dexron II equals to ATF II generally, Mobil uses the title "220" instead of Dexron II.

Regarding the differential, I renewed the oil last year. I didn't know the previous fluid type, but stuck to the manual and changed it with Castrol Hypoid SAE90. Now, I will change the fluid anyway since a very low noise is coming from the back, although I don't exactly know the actual source of the noise. It is highly possible that the noise is not coming from the differential since this humming like noise is not constant, it is coming and going rarely. Nevertheless, I want to eliminate the possibility of differential. The winter time does not go under 5 degree. So, does SAE140 sound better in any case?

[97 SL320]

140 in the diff is going to reduce fuel economy dramatically and possibly prevent proper oil circulation due to it's thickness, use the 90.

For fluid flow, have a look at my posts here

https://www.peachparts.com/shopforum/mercedes-benz-performance-paddock/395119-differential-cover-testing-gale-banks.html

https://www.peachparts.com/shopforum/diesel-discussion/391894-717-400-getrag-5-speed-idle-noise.html

[Stretch]

General service announcement:-

Historically "oil threads" have been a problem on this forum - so I'd like to remind everyone to chill out if it kicks off!

[Stretch]

Originally Posted by racing3000

... since a very low noise is coming from the back, although I don't exactly know the actual source of the noise. It is highly possible that the noise is not coming from the differential since this humming like noise is not constant, it is coming and going rarely. ...

If it is a droning noise then an oil change is a good place to start - though I'd also look at the condition of the rubbers on the subframes (plural for your car I believe), the engine mounts, the flex discs on the propshaft, and the centre propshaft bearing.


I assume it isn't tyre noise?

[racing3000]

Yes, correct, the subframes are plural, but completely changed with the new Meyle ones only 3 months ago. The flex discs and 2 center bearings of the propshaft are also changed with the new ones. The flexible discs and one of the bearings are original. The other bearing is Febi, but a very old manufacture, quality is good. Engine mounts are also Meyle and new. Tyres are only 2000 miles and continental. So, I really get confused regarding the noise. The biggest question is, it is not actually droning and not constant.

[racing3000]

Originally Posted by 97 SL320

140 in the diff is going to reduce fuel economy dramatically and possibly prevent proper oil circulation due to it's thickness, use the 90.

For fluid flow, have a look at my posts here

https://www.peachparts.com/shopforum/mercedes-benz-performance-paddock/395119-differential-cover-testing-gale-banks.html

https://www.peachparts.com/shopforum/diesel-discussion/391894-717-400-getrag-5-speed-idle-noise.html

Thanks a lot for the information. Do you have any idea regarding the noise?

[Stretch]

Originally Posted by racing3000

Yes, correct, the subframes are plural, but completely changed with the new Meyle ones only 3 months ago. The flex discs and 2 center bearings of the propshaft are also changed with the new ones. The flexible discs and one of the bearings are original. The other bearing is Febi, but a very old manufacture, quality is good. Engine mounts are also Meyle and new. Tyres are only 2000 miles and continental. So, I really get confused regarding the noise. The biggest question is, it is not actually droning and not constant.

One thing that isn't in the FSM but is an important part of replacing the resilient parts of these Mercedes suspension and driveline systems is to do the "bounce and roll" technique.


After replacing resilient parts the propshaft often sits in an awkward position - may be a bit squashed or compressed. This can cause weird driveline noises.


The best thing to do is to loosen the centre propshaft big nut and the centre bearing mount. You then need to bounce the car on each of its four corners like you are testing shock absorbers and then roll the car backwards and forward for a few meters. Without lifting the car crawl under the car and tighten the nuts you've just loosened.


This usually fixes this kind of trouble,

[97 SL320]

Originally Posted by racing3000

Thanks a lot for the information. Do you have any idea regarding the noise?

It is difficult to diagnose noise remotely. Does the noise sound like a dry roller skate bearing or a noise that changes pitch while driving? Is the noise tied directly to wheel speed or drive shaft speed? Drive shaft speed would be roughly 3x of wheel speed.

Don't just throw oil at it, diagnose.

[DieselPaul]

I wouldn't bother deviating from what Mercedes said to put in it.

ATF3 superseded 2, and 2 is basically non-existent in the US. All my manual gearbox Mercedes that call for an ATF fill I put Dex3 in because that is what is available with no problems.

As for the diff, it doesn't make any sense to put way thicker oil in just to do it. Straight 90 can be tough to find sometimes, I put 75/90 or 80/90 in mine with no issues. I think eventually Mercedes spec'ed an 85/90 which you can buy from the dealer but its fairly expensive, I only run that in my more expensive cars.

[racing3000]

Originally Posted by Stretch

One thing that isn't in the FSM but is an important part of replacing the resilient parts of these Mercedes suspension and driveline systems is to do the "bounce and roll" technique.


After replacing resilient parts the propshaft often sits in an awkward position - may be a bit squashed or compressed. This can cause weird driveline noises.


The best thing to do is to loosen the centre propshaft big nut and the centre bearing mount. You then need to bounce the car on each of its four corners like you are testing shock absorbers and then roll the car backwards and forward for a few meters. Without lifting the car crawl under the car and tighten the nuts you've just loosened.


This usually fixes this kind of trouble,

Thank you. This method sounds really interesting and seems very comfortable as well. Let me tell you some details about propshaft adjustment. Before the final position and adjustment of the propshaft, there was a vibration at a reasonable level. Then, we loosened both of the big nuts of the center propshaft. I drove the car at this situation nearly 20 miles. Then got back to the garage and the nuts were tightened. Unfortunately, the vibration got worse. The balance adjustment was done again until it totally lost. Now there is no vibration, but this disturbing, deep and friction like noise still comes from somewhere at the back. BTW, before and during all these changes the noise could sometimes be heard and sometimes not, just like now.

Coming back to your method, it is not so difficult for me to apply what you describe. I will do it at the weekend and let you know regarding the result.

[racing3000]

Originally Posted by 97 SL320

It is difficult to diagnose noise remotely. Does the noise sound like a dry roller skate bearing or a noise that changes pitch while driving? Is the noise tied directly to wheel speed or drive shaft speed? Drive shaft speed would be roughly 3x of wheel speed.

Don't just throw oil at it, diagnose.

A very good question, thanks! I forgot to describe the noise, it really sounds like a dry roller skate bearing. I cannot clearly tell you it is tied directly to speed or not. Because when the car is under 20-25 mph I cannot hear the noise. From this point, it seems to be tied to the speed. However, the noise can be clearly heard (but not always, sometimes there is no noise) between 30 and 50 mph without any fluctuation in the sound volume. Above 50 mph, it is impossible to hear the noise due to the road and wind noise. This time it seems wrong to say that it is tied to speed.

I agree you, I won't change the dif oil before the diagnose.

[racing3000]

Originally Posted by DieselPaul

I wouldn't bother deviating from what Mercedes said to put in it.

ATF3 superseded 2, and 2 is basically non-existent in the US. All my manual gearbox Mercedes that call for an ATF fill I put Dex3 in because that is what is available with no problems.

As for the diff, it doesn't make any sense to put way thicker oil in just to do it. Straight 90 can be tough to find sometimes, I put 75/90 or 80/90 in mine with no issues. I think eventually Mercedes spec'ed an 85/90 which you can buy from the dealer but its fairly expensive, I only run that in my more expensive cars.

Many thanks. I will take your comment into account and be much more comfortable while choosing the oil type anymore

[97 SL320]

Originally Posted by racing3000

Because when the car is under 20-25 mph I cannot hear the noise. From this point, it seems to be tied to the speed.

The speed at which the noise starts would generally indicate parts that turn at wheel speed. Parts like differential side bearings , wheel bearings.

Parts that turn at drive shaft speed, like drive shaft center bearings, differential pinion bearings, output bearings of transmission generally start to make noise at 5 MPH.

Your other post speaks of both center bearings being changed. A center bearing attaches to the drive shaft and is bolted to the body. It sounds like you changed bearings / bushings on the end of the drive shafts, these won't make noise.

Originally Posted by racing3000

However, the noise can be clearly heard (but not always, sometimes there is no noise) between 30 and 50 mph without any fluctuation in the sound volume.

Bearings tend to always make noise constantly, this complicates diagnosis.

In cases like this, inspect everything you can and drive the car until the noise gets worse, something fails.