Should I or shouldn't I ?
 

I have an 1986 300sdl with 120,000 miles. My mechanic used to recommend not changing the tranny fliud. He has recently passed away. My new MB mechanic says I should change the oil and have the tranny flushed. What do you guys say? Thanks

My old 90 dodge van had 279,000 miles and I took it to have the fluid and filter changed. The trans shop wouldn't do it. They said over 200,000 not to touch it anymore. I followed their advice.

The shops don't like to touch 'em, because they're old enough that they could fail at any time, and if you're the last one who worked on it, you're going to get blamed.

Do change the fluid and filter, don't flush it. Use the same fluid as has been used is preferrable, a new formulation with different seal swell characteristics can cause problems.

I had attempted to have the fluid changed on the '86 about one year ago. If you are going to change the fluid, it's mandatory to drain the t/c in the process. However, we could not find a drain plug on the t/c for the SDL and, therefore, I had to resort to the flush.

So, if you are going to drain it.........see if you can locate a drain plug on the t/c. There is another member who also failed to find a plug on this vehicle.

If you cannot find the plug, you're forced to flush it. Leaving three quarts of old fluid in the system is not what you want to do.

Recommend changing trans oil and filter. Do not know about flushing. Oil is easy to drain using pan plug. Some quick oil changes can help take the place of t/c drain if not done. I found trans maintenance records scribed in pan.

256k on my tranny so far....had it re-sealed at 213k and they said it had very little wear inside. I changed the fluid around 225k to synthetic, and will be changing it again in a few weeks. Full drain, pan, filter, torque converter, 8 new quarts of Mobil 1 Synthetic ATF and filter kit. :D

Note t all about the T/C drain plug. If the T/C is not the original, for some reason, or another, it may not even have a drain plug. Very often, aftermarket units, or even factory replacements, do not have this feature. I don't know why, but I do know I've seen it, first hand on a lot of occasions. If the car has ever had the tranny, or just the torque converter changed, for whatever reason, there's a high probability it won't have one.

A note:
I have not yet found a reputable auto-tranny shop which recommends tranny flushes, I'm told that they have potential for trans damage. It is preferred to just change the pan fluid a couple of times instead.

Maybe that explains it. The trans on the '86 has definitely been replaced at some point in its life. We searched for that plug for 15 minutes and never found it.

What's the potential for damage? Fluid goes in one side and comes out the other side.........very low pressure system.........engine is not running.:confused:

I don't know, contamination? Overfilling? I've asked the question of transmission techs and that's something they actually seem to agree on. I guess I should have spent more time and asked why.

I definitely agree on overfilling, however, that problem is not unique to a flush. They can just as easily overfill it with a conventional pan drop and refill.

Contamination is certainly a possibility........but.........the oil comes from the same 55 gallon drums that they use for the conventional fill..........:confused:

Yes, but isn't there the off chance, that you could end up with an air pocket in the system anyways? I mean If you drain everything like that, will it take a little while, for the fluid to get everywhere?

I think that's an unlikely event. Once the engine starts, the fluid fills all cavities and the air is forced back toward the reservoir at the top of the pan.

If that were an issue, they'd have a hell of a time with every new vehicle that leaves the factory.

Gotcha, Thanks, I alays worried for the first fw miles or so, if all systems in the tranny were completely "Go". As many tranny jobs as I've done, it's always been a concern, and I've aways kept checking the fluid, to make sure it was still topped off, for th atleast the first hundred miles or so.. Probably been unneccessary though.