4R70W slipping?

[RIP 112]

Wuz Up, I got an 03 GT with a 4r70w auto in it. About 8 months ago I had 4:10 gears installed and a Diablosport Predator in order to compensate for a speedcal. I'm not saying I'm a crazy driver, but when I drive casually, the transmission shudders when the converter locks in to overdrive. It only does it going in to overdrive. Also noticed is that when I let off the gas and coast from 70mph down, the rpm jumps up and down constantly from 2200rpm to 2000rpm until I get under 30mph. It's been happening lately, but this doesn't happen always. I would take it to my dealership, but like I said, it doesn't happen always, and I don't want to risk it not happening and looking stupid. The car hasn't thrown any codes, and I turned the shift pressure/ torque modulation down to stock settings, but it hasn't changed. Anybody have this problem? Any braniac know what's going on and can tell me? Do ya'll think this can be a warranty issue? My dealership installed my gears, if that's part of the problem. Thanx.

 

[FriscoGT]

Mine was doing the same thing. When I had the fluid changed there was metal in the pan. When I went to Ford, all I really had to say was "Overdrive" and "shudders when hot". They looked at it and no questions asked had it rebuilt (mainly overdrive band and new torque converter)as well as gave me an extended powertrain warranty. I think the 4R70W is pretty notorious for this, unfortunately. BTW, no problems since in 30K miles. It still does not shift firm, and might consider a shift kit once my extended warranty runs out.

 

[bdcardinal]

when was the last time you changed the fluid? you should really do it every 15k miles if you drive your car hard. i would suggest getting a synthetic ATF such as Mobil 1, Redline or Amsoil. when you do teh fluid change make sure you change the filter as well. i dont think the mustangs have a drain plug in the TC so you will have to drop the pan, replace the filter, put the pan back on, drop in like 4 quarts and then do a flush with the cooler lines off(if you are doing it yourself). if you take it to a quicky place, they probably wont do the filter, even if you ask. hell when i was at the dealer we never did the filter even if people asked for it. just do the filter yourself, and then take it to a place to have a full flush done. make sure that they use Mercon V compatable fluid, not just Mercon or Dexron3.

 

[OinkAodeOink]

mine does this also..Im at 45k and probably in need of a trans flush and filter. Im sure thats all your problem is.

 

[SeanD1111]

when was the last time you changed the fluid? you should really do it every 15k miles if you drive your car hard. i would suggest getting a synthetic ATF such as Mobil 1, Redline or Amsoil. when you do teh fluid change make sure you change the filter as well. i dont think the mustangs have a drain plug in the TC so you will have to drop the pan, replace the filter, put the pan back on, drop in like 4 quarts and then do a flush with the cooler lines off(if you are doing it yourself). if you take it to a quicky place, they probably wont do the filter, even if you ask. hell when i was at the dealer we never did the filter even if people asked for it. just do the filter yourself, and then take it to a place to have a full flush done. make sure that they use Mercon V compatable fluid, not just Mercon or Dexron3.

The man is correct! It is called Torque Converter shudder, and usually a tranny flush will solve the problem. I also agree that a good synthetic will do wonders, but a tranny cooler will be the best for the tranny.

 

[RIP 112]

Thanks alot guys. I'm taking it in to my dealership and see what they'll do. Thanks alot for the info.