Welcome to the joy of w140 tranny ownership.

(Like everything on this car - when it works, it's the best... when it doesn't work, it's expensive...)

Phoenix Reman Trans will sell you a rebuilt tranny for about $1400. (This is the least expensive I have found from a "big transmission rebuilder" kinda place). Also, they have a tranny dyno, so in theory you would know that the unit was put together right prior to it leaving their facility. They also have some ***** on the web (there is a site www.phxreman-sux.com), but when you do the volume they do (several 1000 trannies per year), you are going to have a few deals that went bad.

I found a small indy shop (German Transmission Company) and they (he, one man shop) did the job (total, including resealing the main seal on the engine) for $1400. From my research, this price seems too good to be true, but so far, so good.

In the end, I think you will find that doing a full rebuild (either by rebuilding yours or trading in a rebuilt unit) is the way to go. From there, you can pay what you want (as long as you pay lots or lots and lots), so I would look at warranty and other signs of good faith. A good independant shop (doing the R&R) and sourcing the trans from a national place (like Phx Reman or (I think) Metric Mechanix) is probably the best deal. (Should run about $2500 total).

Of course, if you are near Phoenix, German Trans is by far the least expensive...

-David