transmission mystery

[lyle_H]

At cooler temps in Austin and San Antonio my transmission in the 1987 420sel that I love will actually slip into reverse. When the operating temperature rises to 80C then there is no such hope of sliding into reverse.

Now I believe that transmissions don't necessariy like new fluid and this has happened for the past year or so. When I first traded for the vehicle, I would slide into reverse after a minute or so on a cold morning, but as the temp warmed up, no chance....

I changed the fluid and added a Lucas Transmission Oil thickener thinking that doing so might help the issue....no such luck...now december and I am back to sliding into reverse early in the morning but that is it....

Ideas anyone?

Lyle in Austin