Auto Tranny fluid - PeachParts Mercedes-Benz Forum

NoSparkNeeded · #1 03-24-2010, 05:17 PM

I going to change the fluid and filter in the TD and SD this weekend. Should I just get the latest mercon/dexron or bust for the synthetic?
I change F/F every year anyway, so is the extra money well spent on synth?

latitude500 · #2 03-24-2010, 06:05 PM

You’re going to get a lot of different people talking about their favorite flavor of products so keep your flame suit on. HAHAHA
I really like amsoil products. I use a 3rd party oil analyzes and its always worked out great. If you have some free time start doing some reading on the products that they provide.
http://www.amsoil.com/
http://www.amsoil.com/storefront/atf.aspx
I really don’t think it’s worth changing out every year. But that is just my two cents.

layback40 · #3 03-24-2010, 07:54 PM

We change it (& filter) about every 5th engine oil change in the cars. Its worked for us for near 30 years.
We have never used synthetic fluid.
Our earth moving stuff has mainly Allison/Cat trans & so operate the same as an auto, again we just use regular fluid (different grade) in them.

Gilly · #4 03-24-2010, 08:39 PM

Not worth it if you are getting the same service out of it.

JHZR2 · #5 03-24-2010, 10:19 PM

synthetics do offer advantages. That said, normal Dex III shears down fairly quick, but is cheap. Dex VI is the only current dexron spec, and may or may not be relevant...

I like synthetics, but do not like the one size fits all specifications which many of them carry.

NoSparkNeeded · #6 03-25-2010, 10:35 AM

Then I take it that the Dex 6 is okay for our older cars? I went to auto zone and unless I'm mistaken they had Synth for only a buck and a half more per bottle than the Dex 6.

JHZR2 · #7 03-25-2010, 10:44 AM

The funny thing with Dex VI is that given its shear stability requirements, it can only be achieved as a syn. Perhaps some of the lower-end ones are blends, cant say for sure, but a syn fluid is ever-more necessary for these advanced ATFs.

Dex VI is back-specified for the obsolete specifications of dexron, i.e. Dex IIIH and III, IID and II, and Dexron. Going by that logic it would be suitable for use in places of the specified Dex II for MB ATs.

However, the reality is that it is back-specified for obsolete Dexron in GM ATs, and depending upon how you want to let your logic process proceed, this may or may not mean that it is relevant for non-GM ATs, where some nuance with clutch material or similar may exist. There is no language apparent which allows Dex VI to be back-specified for MTs that were specced for ATF or some Dexron form.

Ive not personally tried a Dex VI in my MB ATs. I am running it in a Chevy truck specified originally for Dex III, and am happy with it. Likely there are no issues, as the Dex VI starts at a lower viscosity which a regular Dex III would shear down to within 10k or so... My main question is what was the actual typical design viscosity of the MB ATs.

pawoSD · #8 03-25-2010, 06:41 PM

Quote:

Originally Posted by NoSparkNeeded

Then I take it that the Dex 6 is okay for our older cars? I went to auto zone and unless I'm mistaken they had Synth for only a buck and a half more per bottle than the Dex 6.

That is what we have in all 6 of our MB's....works great. I use the Valvoline stuff. Dexron VI Full Synthetic....

Hit Man X · #9 03-26-2010, 11:21 AM

Cheapest Dex III I can find, no issues. Just change it every few years along with the filter. Maybe $25 in materials.

Toss in a magnet inside the pan to attract the crap that floats about too.

Palangi · #10 03-26-2010, 08:37 PM

Where do you find real DexIII nowadays ??

JHZR2 · #11 03-27-2010, 06:26 PM

Dexron III is an obsolete specification. GM no longer gives out approvals to this. Dexron VI is the new specification that is being given approvals. It is supposedly back-compatible to dex III and II, as well as original dexron, but there may be reservations. It holds no approvals for back-specification in MTs, and it is questionable if use in non-GM ATs is 100% acceptable. Dex VI is far more shear stable, but also starts at a far lower operating viscosity.

Mainline brands selling a D/M or "ATF" generally are dex III fluids without license/approval since they are obsolete. Do read the bottle to verify you arent getting something else.

JHZR2 · #12 03-27-2010, 06:44 PM

Quote:

Originally Posted by pawoSD

That is what we have in all 6 of our MB's....works great. I use the Valvoline stuff. Dexron VI Full Synthetic....

Good data point, did you notice any changes in shift quality? This is aconcern especially in manually controlled ATs, where there is no overarching control verifying shift timing, etc.

It would be interesting to see before and after uoas for dex III and VI, I might do that in my 300cd. If the at was designed for say, an 8-9 cSt, a fluid like VI may be a bit too light for full wear protection at 6-7 cSt... Sothen the add pack is more critical, and that can be a tough thing in ATs where the friction material comes into play...

NoSparkNeeded · #13 03-27-2010, 07:17 PM

I got 14 quarts of Valvoline DEX 6 for 5.31 per quart. I haven't changed the fluid yet. It says compatible with DEX 3 spec. Is there some question about using it in older Mercedes transmissions? How many folks here are using it in pre 1985 Benz trannys? I use it in my 86 Jag just fine, however that tranny, is in fact a TH400 GM.