tranny swap??

[126nut]

First time poster here!!,

This looks like an excellent forum, lots of down and dirty tech questions and not a bunch of fluff, exactly what I have been looking for.

Now, a question please,

I just bought a 89 420 SEL with 125 K on the ticker and it has the slow tranny engagement syndrome, from park to drive and reverse, vice versa. Seems to shift well when underway and as far as I know it is still the original trans, got all the records with the car. I did a complete filter and fluid replacement, not a flush, drained the TC and all. It still is a bit slow to engage, probably needs a going thru, right? No trash in the pan, just a small amount of normal sludge. I have rebuilt a 380 SEL trans and have a ATC book which talks about bad piston seals but would really rather not get into another one, it was expensive, almost a grand in parts!!

Here is my real question, I have almost free access to a freshly rebuilt tranny out of a 85? 500 SEL Euro, would it work in my 420??

Thanks,

Chas