83 240D Manual--Merits of ATF vice Gear Oil in Transmission?
 

I often wonder why people keep saying that you should put ATF in that manual transmission, it makes no sense. Won't it even affect transmission performance? I never had problems with my manual until I tried ATF!!
Recently, I couldnt even downshift from 4 th gear to 3 rd Gear.
Perhaps I have a damaged Synchro, but before i tear down the transmission, i would like to put Gear Oil in it and try it..

83 240D Manual--Do I put ATF or Gear Oil in Transmission?

The MB manual that came with my 409d 5spd manual clearly states that ATF should be used in the transmission.

Can you downshift when you double clutch?

Besides lubrication, there are two other properties of the lubricant that can affect long term preformance and life of a transmission. One is compatibility with the seals. The wrong fluid may harden, soften, or swell the seals.

The other is its effect on brass components. I work with lubrication engineers and one of the lubricant properties tested in our lab is the copper strip corrosion test. Lubricant cannot be too aggressive on brass if brass is present in the unit. Last friday I had a good discussion about scuffing of materials in the presence of a lubricant. If the lubricant doesn't have the proper antiscuffing agents or is chemically reactive with brass, over time it can destroy the transmission. The synchronizer mechanism has unique demands of the lubricant because it IS brass and it depends on frictional contact with the mating cone surface.

So you can see a lot of factors are considered when specifying a lubricant for a particular transmission. A lot of people get into trouble when they try to reengineer a car without knowing what they are doing. Repair your transmission and stick with the specified lubricant.

If I read between the lines correctly, you ran gear oil for a long time before switching to ATF. I suspect the synchronizers were being slowly damaged during the time you used gear oil, and the problem now cropped up when - only by coincidence - you switched to ATF. Or the problem is unrelated to lubrication. If the problem goes away by switching back to gear oil, more power to you. But I suspect the problem will stay.

OK, ATF then. But what type / brand of ATF? Is Type A ATF still available?

Ken300D

JimSmith uses Redline ... and I just bought 2 quarts for mine also....

#1 reason for ATF..... needle bearings on gear shafts wont get properly lubed by 80-90wt. gear oil. Btw, MB has been using ATF in manual trannies all the way back to the 1960's - or as long as i can remember.

The proper oil is ATF. DexronII/III is fine but will be stiff in cold weather. I REALLY much prefer Mobil 1 ATF. It's MUCH better than Redline in MY OPINION - and I've compared them in two different MB 5 speed manual transmissions - I drained out the Redline and immediately filled with Mobil 1 and the improvement was immediately evident. quoted from a larger documant written by Dr. Eric Chowanietz.

If your transmission is already damaged then you whatever works for as long as it works I guess.

Marshall

NO, NO, NO! The manuals from years ago specify ATF, yes. They had no way of knowing when they printed them, that ATF was going to radically change for their application, an automatic transmission.

If you are going to INSIST on using ATF, DO NOT USE DEXRON OR MERCON. These are the ones that have changed to a point of causing seal damage.

You will be better served using Redline Manual Transmission lubricant or motor oil. My 240D has gone something like 400,000 miles on 10W30 Mobil One with NO PROBLEMS.

If you MUST use ATF, find some type A.

Good luck,

I agree that 10W30 Mobil 1 is just fine and so is Mobil 1 ATF! Both (in my opinion) are actually superior to type A (I have compared them directly with type A in the same transmission). You must NOT use any gear oil with EP additives (most manual transmission oils DO contain EP additives) as these will cause errosion of the synchronizers and most gear designed for manual transmissions oils are too thick for an MB box. There is NO incomaptibilty between the seals in Dexron II/III ATF and the seals in an MB manual transmission (at least throught the 716/717 series), but it is very stiff in cold weather. Mobil 1 10W30 will reduced seal leakage and I believe Mobil 1 ATF will as well.

Here's some more from Eric on 236.2 oil:

Marshall

This would be a great question for a factory rep at an MBCA meeting.

:)

Ken300D

I'm giving some consideration to using this for the manual transmission oil.............

Ken300D

The application that catches my eye is ZF transmissions, exclusive of Hypoid Gears. Does the MB ZF transmission use hypoid gears?

Ken300D

Couldn't get all the applications on a JPG small enough to post. Here is the second half of the applications list. (After all, isn't the 240D just a fancy tractor?) :)

Ken300D

Ken, I don't think you're getting the idea. The EP antiwear additives used in the vast majority of transmission/gear oils will DAMAGE the synchronizers used in Mercedes transmissions. The additives used in ATF will do no damage and will preserve the synchronizers. Most gear/transmission oils are too viscous. Most current Dexron/Mercon fluids - especially in cold weather are a little too "thick" too (the 4-5 speed used up until the mid '90s were all intended to be run on type A fluid which was a little less viscous). Gear oils in the 75-90 range are plainly too "stiff." Mobil 1 is a little stiff at some temps, but it's superior temperature/viscosity characteristics actually makes it better than type A in very cold weather and slightly inferior over a narrow range and superior at high temperatures. All in all I MUCH prefer it even to type A. You can of course pay the premium for the Mercedes approved product and get a fluid that I find inferior to the Mobil 1 ATF. None of the ATFs (or even engine oil) will damage the synchronizers like EP gear oils will.

Marshall

The original owners manual for my 1979 240D specifies "Engine oil SAE 10 W/20 W-20" for the manual transmission.