I assume these auto trannies are a bit stronger than ten years ago, but the old 4R70W auto trannies built in the mid 90's had issues when doing a WOT downshift when in overdrive -- many posts about this in the Mark VIII forum. IIRC, one of the shafts in the tranny would twist and break when shifting from OD to 2nd ( although it was just a 4-spd ), too much torque to handle I guess......

Not that this is necessary in an S197 Mustang, but I'd always hit the OD button to get my Mark VIII in 3rd before getting on it at highway speeds.......

 

Ford used that 4R70W in the F-150's until 04 Model year i believe and that thing could not handle the torque of the 5.4. I know many people who have snapped that intermediate shaft and I know a few that even upgraded it to a heavier version and still snapped it.

Richard

 

I too use that O/D button, fairly frequently too.
I concur it "speeds up" the response of the downshift from 4th to 3rd.
Also I don't have to stomp on the gas too soon to get to 3rd that way.

I'm also guilty of using the shifter to get into "3" on occasion for even more shenanigans but I only do that under 50MPH or so. I still worry this bit of fun could somehow cause damage, though.. I've been known to trash a couple Explorer auto trannys in the past for shift behavior..

 

The 4R70W is rather weak. I know many people who claim their friend's brother's sister's uncle ran X seconds on the 1/4 mile with 9000 hp with the J-mod and some modified internals, but let's be realistic. A lot of the State Police/Highway Patrol Police Interceptosrs that are auctioned with 100k miles has had at least ONE transmission replaced. Then there are the 4R70Ws operated by old people that experience torque converter clutch failures or slippage issues. I have yet to find an automatic transmission that I liked, which is why I went to the dark side and got my Stang with a TR-3650. Now I cannot fathom ever buying a vehicle with an automatic, and I find myself stabbing for the clutch and grabbing for the shifter in a vehicle with an automatic (CVPI, HMMWV, whatever).

I recall there being a modified 4R70W, the 4R75W, and then the 4R75E used in the latest Grand Marquis / Town Car / Crown Victoria.

My gripes about the 5R55S are that it is French, and it's an automatic.