99 - swapped 99 tranny for 04 - speedp off and shifts WAY to early. help please

Bryanc4321

New Member
Jul 8, 2008
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San Diego
Hi, new here. I just changed the Automatic transmission in my 1999 3.8L V6 for a 2004 Auto transmission (also from a V6) i got at a junkyard. I called the dealer and they said that the trannys themselves are both the same and the swap should be fine. Everything went as planned with only one exception and that is that the speed sensor had a different style connector on the 04, same 2 wires, just a different plug. I spliced the 04 connector into my 99 wiring harness (I didn't just swap the sensor because the 99 sensor was melted) then I took it for a drive.

It shifts way too early and when I am going about 25mph, the speedometer says I am going 100mph. I'm thinking 1 of 2 things, either get a 99 speed sensor, or does the computer need to be reprogrammed?? Or is it something else entirely? The car is bone stock, what would be the cheapest way to solve this issue? Any help would be appreciated, thank you!!
 
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I'd get a 99 speed sensor either new or from a junkyard and try splicing it in. Sounds like the two sensors are calibrated differently. Problems like this are common when replacing a componant with an "identical" one from another year. There are always little engineering changes made from year to year, and sometimes even the mechanics don't know about them.
 
Followup:

Thank you for the reply, as a matter of fact, I just got back from the hobby shop and did exactly that, but with no luck. same problem. I called a local transmission shop I was reffered to and they told me that I had 2 options, get the correct year tranny or purchase an after market computer calibrator like a "Baumann" programmer. The programmer would fix the problem, but he couldn't guarantee that it may lead to other problems or "codes" popping up because of the interrelation with other systems. Furthurmore, they could not do it there do to legal issues with emmisions and speedometer modifications. The programmer cost 250.00 online, but I can go back and swap my tranny for the correct one for free, I'll just have to spend more labor correcting the issue. Oh well...I actually learned a lot about AODE trannys in the process. Lessons learned :rolleyes:
Thanks again for the assistance.