So what parts would I have to swap to put the 85 500SEL trans in the 89 420SEL? Here's the deal..... I have a running driving 420SEL that has idle, electrical and body damage issues. The 420 runs great off idle but idles pretty rough. So I hate to throw it away. And I'm looking at an 85 or so 500SEL that the owner says is in nice condition but the trans only goes 1-2 and won't go into 3rd or 4th. I hope to drive the 500SEL later today. Anyway I was thinking about what it might cost to repair the trans on the 500 and what the car might be worth. But if the trans on the 420 will fit the 500 that might be a solution. I really like driving the 420 but it's pretty rough. However if the 420 will move under it's own power it's worth quite a bit more than if the trans is out. So I'd prefer to put the 500 trans in the 420 and keep the 420 as a self ambulatory vehicle. Or maybe there isn't anything seriously wrong with the 500 trans.