04 Gt Motor And Tranny Swap Into 02 Gt Gone Wrong

[Nate0428]

Hi I am new here so sorry if I'm posting in the wrong place but I really need some help.
So as the title says I swapped a motor and trans from a 04 gt into my 02 gt automatic from what I read it should have been as easy as plug and play so I left it at the mechanic shop but got it back with a series of problems first thing I noticed is the speedo goes from 0 to 150 really fast at about 20 mph I'm reading 80 mph on the speedo second thing is the transmission seems to compensate for that by shifting from first to third or final gear I'm guessing because the computer actually thinks it's going that fast so it skips second gear unless I manually shift it my self and my miles literally count like seconds I'm almost at 400,000!!!!! Started at 150,000 the shop I left it with was and is no help they keep trying to say the trans I gave them was bad but I drove it before it was pulled and both motor and trans only had 40,000 miles on them if anyone on here has any advice or input I would greatly appreciate it thanks for your time

 

[Davedacarpainter]

Hey Nate, welcome to stangnet.

Yeah, that's some problems there alright. I'll move your thread over to the '96-'04 tech subforum. The guys there will be able to help you out.

Good luck, I hope you get it fixed soon.

 

[wmburns]

I swapped a motor and trans from a 04 gt into my 02 gt automatic from what I read it should have been as easy as plug and play

The problem is the motor is a "plug and play" but the transmission is not. There are differences in the automatic transmission between 2002 and 2004 model years. Further I believe that the transmission in the 2004 model year is a 4R75W where as the 2002 came with a 4R70W. There are differences in the set up and OSS speed sensors as the number of teeth are different. You are correct that the PCM can not correctly shift IF the speedometer is not correct.

Likely the easiest way to correct is with a tune similar to a rear end change. However, the turbine speed sensor may not be so easy to correct.

 

[Sluggie24]

In 2004 ford changed the output speed sensor and the planetary annulus gear. This changes the way the computer reads vehicle speed and the computer uses speed to shift the trans. If you are set on using that trans, it will have to be removed and the annulus gear replaced with one from a 98-03 4R70W. It is attached to the output shaft so it is the very last part to come out of the case meaning a whole tear down. You can reuse your original sensor.

The older units read speed off of holes in the gear while the 04 reads off of extended parking paw lugs. The sensors are different because of the change as well.

 

[Nate0428]

OK thanks for all the info guys I'm not set on using this trans just trying to get it fixed asap any recommendations on what the easiest way to fix this would be?

 

[Nate0428]

OK thanks for all the info guys I'm not set on using this trans just trying to get it fixed asap any recommendations on what the easiest way to fix this would be? Just find a 02 transmission for sale maybe?

 

[Sluggie24]

If you still have your old trans and it works then swap transmissions.

It's also possible that a tuner could use the software from an 04 and put it into your computer but don't quote me on that. I don't know if the way the speed sensor reads is software or firmware based. It wouldn't hurt to contact one to find out though.

It's also possible that an 04 PCM could be put in your car if a software change isn't possible but don't quote me on that either. I'm not sure if there are any differences besides programming that would prevent that.