That is just the right speed for torque converter shutter, it happens to older transmissions with seals that are getting weak, try putting in some shutter stop, most parts stores have it or can get overnight it usually starts to work in just a day or two at the most. This just causes a symptom, eventually you will have to overhaul the tranny.
Drain the torque converter, new fluid. Works like a charm. I was told to do that by a Ford mech, did it on my '93. Shudder stopped. may need some shudder stop also.
For some reason the rest of my post did not show up. I have owned the car since 2008 and it had that shutter the entire time then last year (2015) the tranny finally gave up and started losing gears (326000+ miles). So I replaced it with another tranny/torque unfortunately also with high millage and it does the exact same thing the old ones did. I drained all fluid out of the newish one and replaced the filter before install. After install, I again replaced the filter for any residual gunk that could have been in it and replaced the trans control solenoid and trans speed sensor because they were relatively cheap and simple enough to replace by myself. I am just concerned about spending an additional 150 for a torque converter if there is any chance it could be a simpler fix. I know with these 4R70W trannys that overhaul is always eventual I just don't want to speed up the process. Thank you for your suggestions I will certainly try these out before going further into it.
The shutter stop will not speed up the process, if anything it will delay it. Shutter stop and TransX are both products that I have used and if the tranny is not too far gone they can help.
There is a drain plug on the torque converter (unlike other cars). One has to turn the engine over by hand until it shows up in the bottom hole. no need to remove trans.
Very helpful Trippmeister.
Thanks! I had my Wife clicking the starter until the plug showed up, then moved it by hand to the right location. If I remember right, there was a rubber plug in the housing.
Looking for a Used Grand Marquis in your area?
CarGurus has 8 nationwide Grand Marquis listings and the tools to find you a great deal.
Search Mercury Grand Marquis Questions
Mercury Grand Marquis Experts