odd clunk coming from trans?

4.6boy said:

i got a 02 gt .with a intake, american tunder catback and 373 gears. when i got my gears installed i used a sct tuner(the one with the loaded tunes)i first used the 93 tune and did noting but set it for 373s. i then toke the car for a drive and noticed that when i was just cruiseing if i would go even a little wot it would make a clunk(sometimes its more then one clunk in a row) that comes from under the car. it does not do it in park or if i run the car with the stock tune. the car runs fine idles like a champ but that nosie is killing me does any one have any ideas as to what it can be its an auto with 74000 and when i bought the car 2yrs ago ford replace a tailshaft housing and troqconvert or so they say cause it was under warrenty.

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does it do this when you first get on it? and if so how fast are you going when this happens? Does it do it during or after a upshift?

Did it do it before you got the tune? Does it clunk on the down shift? I contacted a very reputable 4R70W builder concerning the clunk and here’s the answer he gave me…

"We have fought that downshift clunk ever since it first showed up around 2002. The issue is in the computer program and is addressable through tuning to some extent. This happens both with aftermarket tunes and on the stock tune if the vehicle is prone to it. The ‘problem’ is made MUCH worse if the car has been tuned and the tuner is using SCT software and simply uses the base SCT transmission value files. What is going on is that for whatever reason, maybe due to adaptive learning we just don’t really know, the computer is causing a line pressure spike on that downshift. It’s potentially annoying but it won’t hurt anything. "

My trans started to clunk right after I got it Dyno tuned so take it for what its worth.