71 280sl Transmission shifting problem

[rbsl280]

I had the car tuned up last year and ran great.  Recenly the car will not shift without pumping the gas pedal and slowly.... gets up to speed on the highway.  Sometimes it will surge and shift hard.  It is a new phenomenon.  Was told the gaskets need to get replaced as they have dried out.  The car is leaking fluids.  Could it just need more automatic transmission fluid?  If so, how do I know, and how do I add more?  Could it be something else?  Thanks for any help.

Rob 71 280sl

[Cees Klumper]

I recently replaced the oil & filter on my auto transmission and initially put too little fluid in. The car shifted very differently from before. When I topped it off, all was back to normal. Which is to say that I can imagine that not having the right amount of oil in your transmission could be the cause of your problem. The way to check is in the owner's manual, and is: bring the engine up to normal operating temperature, put the car in park with the engine running, car on a horizontal surface, let it idle for a couple of minutes and, with the engine running, measure the fluid level. Be careful with adding fluid, you don't want to get contaminants in there as the auto trans is a sensitive entity.

[graphic66]

The auto tranny is so sensitive to contaminants that the owners manual says to wipe the dipstick off with a piece of clean leather. This is to keep any lint that would be on your rag out. Just when you thought you knew all the crazy nuances of SL ownership. Now I have to carry a piece of leather in an airtight plastic bag in my trunk.
    Check the level with the engine running, handbrake pulled, in park [P], on level ground with transmission at operating temperature, Prior to checking let the engine run 1-2 minutes at idle. Pull out the dipstick, wipe it off with your very clean piece of leather, dip in completely for measuring, pull it out and read the level. It should be between the upper and lower dipstick mark.Fill it while running with an ultra clean funnel through the dipstick tube. The distance between the upper and lower mark is .5ltr. for reference.
  You may want to change the fluid and install a new filter and gasket. Also check the rubber cooling lines between the radiator and the lines from the transmission. These can leak some fluid, especially if someone has spliced in some non Mercedes lines.
  It is also very easy to tune your shift modulator pressure to shift to your liking, hard, soft or just right. I am down to about one more 1/2 turn harder to be to my liking. Although of course the best way to set it is with a pressure gauge. You can through experimentation and by keeping notes get it to shift very nicely.