synthetic atf?

[Wasuchi]

I'm getting ready to change the fluid in my 300d, it has 140k+, is it advisable to change to synthetic or should I just stick with the regular stuff? I know this has been covered before, just want to know if anyone has had any problems.

[ricali]

this past summer had a problem with my 240 it just wouldn't shift.
change to asmsoil sth. and it's still going.
problem over
tranny and engine are original with no repairs presently 329,000:p

[MarkM]

I've been using either Amsoil or Mobil one synthetic ATF for the past 125,000 miles..ever since I bought the car....no problems...I replace fluid and filter every year, (approx. 25-30K miles a year).

[Chris Blanchard]

I'm a big fan of Mobil 1 synthetic ATF as well. It seems to have better cold weather behavior, i.e. the tranny is much smoother when starting out when the temperatures are below freezing. I also use it in my power steering fluid reservoir.

Considering that is only costs a bit than the non-synthetic, and you only change it every couple of years (depending on how much you drive) the improvement is well worth it.

Chris Blanchard
1984 300SD 145k

[stephenson]

Oh, yea!

Synthetic ATF.

Synthetic grease.

Synthetic differential.

Synthetic engine oil.

You bet!

Have used all for many years - no issues. The logic of using absolutely the finest lubricants in transmissions and differentials is even clearer than in the engine - they are simply better than any other non-syn alternative - but, since the change interval between trans and diffs is so much longer than between engine oil changes, there is no excuse for not putting in the best.

[harrywat]

Where do you find Mobil Synthetic differential and ATF? I located a source for Delvac 1, but have not seen the others.

Thanks,

Harry
86 300 SDL 106K

[Michael]

I use Redline Synthetic ATF in all of my cars. Great stuff, no leaks

[Wasuchi]

Sounds like a good idea then if nobody has had a problem. I won't be putting synthetic in the engine, costs too much to have it leaking out all over the place.

[Robert W. Roe]

I just switched to Mobil 1 synthetic ATF around 187.5 K miles. I'm still on the first week so it's too early for any long term opinions, but I have put about 500 miles on the tranny since changing to synth ATF.

Shifts are definitely smoother in everyday driving. It seems to take less warm-up time to shift smoothly. Slippage after shifting from R to D I still have, but not as frequently. I still have a brief lag going from R to D or vice versa.

All these things seem better, but maybe (and this drives me nuts after every shift that's a bit firmer than most) it's psychological...you know, trying to reassure myself that paying $4.99 a quart for ATF that is <$1 at BJ's or Sam's is really worth it, but I'd say YES definitely. Re: the question of where to get it?, I found it at Pep Boys, AutoZone, and Advance Auto Parts. All but the latter were $5.99. Advance was $4.99. This was last summer, so don't hold me to it. I had been adding synthetic as my fluid level dropped, but finally convinced my wife and my mechanic that it might be a good idea to change my ATF way before it had to be

To summarize, I've never had such smooth shifting, especially after the drivetrain has warmed up. Now I'm rethinking the synthetic oil question too...

[harrywat]

Thanks Bob Roe, your tip to find Mobil 1 ATF at Autozone solved my problem. I don't go there often because its in a near by town, but I now have a source.

Harry

86 300 SDL

[Robert W. Roe]

Glad I could help, Harrywat. Even if it's 5.99 a quart, I figure it as perhaps a cheap way to get a bit more time out of my aging tranny. The improved shifting is another reason to drop the $$ for this stuff. So far so good. Oh, if you get a shop to do it for you, make sure they do the torque converter as well as the tranny.

I think if you buy 7 quarts you should have enough, but I don't have my books in front of me. I bought 9, figuring on adding some if the level drops. So far no noticable (new) leaks, but then I'm talking about not having any new driveway puddles, not crawling under the car to look for drips.

[RunningTooHot]

If your transmission already has a small amount of leakage due to old, hardening seals -- then you may want to give this shot before changing over to the synthetic.

Go get a can of your favorite "miracle sealer & rebuild in a can" transmission additive (such as Trans-X). Siphon out an appropriate amount of fluid that will be replaced by the additive - do not overfill your transmission. Pour in the additive and drive your car for 50 - 100 miles. This is just enough time to allow the additive to _just barely_ permeate the seals, yet not long enough to cause them to become too soft (which can cause leakage problems later). Then thoroughly drain off the fluid from everywhere; I know its overkill, but I even drained the Trans cooler & lines. Change the filter & fill with your fresh synthetic fluid and you are good to go.

I did this on a four-speed automatic that had a small amount of seepage from the front pump seal & was starting to slip wildly while flaring from third to fourth gear when it was cold. This was almost two years ago, and that transmission is still working perfectly even with the torque of European spec 5-liter engine applied with a heavy right foot! This little gamble has saved me about $1200 up to now -- I know it will need a proper rebuild in the near future, but as long as it running right...

RTH

[haasman]

I just replaced the ATF and differential oil in both my '91 300E (165k) and '95 E320 wagon (75k) with Synthetic Mobile 1. Wow what a difference! Both cars definitely have improved in shifting. The 300E I was wondering whether a rebuild was around the corner. Very noticeable diffrence in shift points, especially in the E320.

I changed the trans filter in both at the same time. The hardest part was finding a 14mm allen socket for the differential fill and drain.

[Robert W. Roe]

Glad to hear that others are getting similar experiences with improved shifting with synthetic ATF. Now I'm all pumped about synthetics everywhere, too... the cheap 5 quart jugs of Mobil 1 at Walmart are starting to tempt me to go with 15W50 synthetic...or should I get 10W30 for northeast winters? ... anyway ... Wondering how much of a cleaning effect the synthetic will have on the tranny, but how dirty does a tranny get inside? I don't know.

I wonder what kind of a difference synthetic differential oil would make? Better power, fuel economy, less wear,, etc? Does anyone know what kind of synthetic differential oil I should get for a 1984 300SD?

[haasman]

I also changed the differential to synthetic using Mobil 1 diff. oil. Quieted the '91 300E noticeably.