Transmission Problem

[NYDEISEL]

This is my first post so if I screw up let me apoligize in advance. My daily driver is a 1979 300SD. I changed the transmission filter and gasket but did not drain the torque converter. Now when I drive the car for about 20 minutes I get a bad vibration if I come to a dead stop and then hit the gas. Only happens when going into first gear. Once you get past first the car drives fine. Does anyone have any idea what is causing this? Am I looking at a rebuild? Please help... Like I said when I first start the car no problems. Only after driving for a while does this happen. This is why I am confused.

[rdanz]

Check your fluid level. Sometimes when a trans has not had the fluid changed for a very long time like years, after you change it it develops problems. Hope this is not the case and I hope you used the correct fluid.

[diesel don]

I've done it both ways. Have drained the TC sometimes and others not. The key would be how much fluid did you put back in?

Don

I can try to explain part of your situation, and
that has to do with the viscosity of the trans fluid.
You said it works o.k. at first but troubles start
after being driven awhile. It takes 6-15 miles
for trans fluid to reach operating temp. When this
occurs, the viscosity becomes less, as with any oil.
If you have an internal leak, the fluid will stay and
go where it needs to when cold, but when hot it
will escape through the leak. The result would be
too low a pressure to get into gear. This is a
very general explanation but proven true with my 300sd.
It would not go into 4th when hot, either I had to keep
it in third or let it slip.
If you happen to decide that your trans is shot and
want to buy more time, put some lucas trans treatment
in, it is like 90weight transfluid. It took 3 quarts for
me but it did shift into 4th for 3000 miles until I was
able to replace the trans. I am not suggesting this to be a permanent cure.