Originally Posted by SignOfZeta
Well, I've been getting that elusive P1870 code for quite some time. The transmission fluid'* turned a lovely shade of red, albeit with a slight burnt smell. Aside from that, when you're on the road, you can't even tell that anything'* wrong with it. It shifts smoothly and when it should, and I've never been locked out of a gear.
I decided to start shopping around for repairing the slipping torque converter clutch. One transmission shop'* mechanic said that he'* seen this code before, and suggested a complete rebuild: all new parts (minus the case), with a two-year/24,000 mile warranty, for $1800 (before tax, 6%).
I've barely begun to shop around, but what do you guys think I should do? The car has no major problems aside from that. I'd rather get this fixed before I end up stranded somewhere and forced to cater to the closest mechanic'* whim.
Have a mechanic drive your car with the computer hooked up to it. You can monitor all of the information to determine how much slip there is and so on. He should be able to determine whether it'* your transmission or the TCC. I wouldn't leave it in the hands of a random mechanic with an $1800 quote without trying to narrow it down more by taking it for a test drive w/the computer hooked up. IIRC correctly, the computer will throw out a P1870 with a slip of about 50RPM. Mine was 200RPM when I got it in. My TCC replacement, bushings, seals, and a little bit more ran about $950.
Your problem seems to be exactly the same as mine was a few weeks ago, as a matter of fact, in every single way. When the light originally kicked, the car had shifted from 4th to 3rd while decelerating. Given your problem is between 3rd and 4th, sounds like a failure to lockup, same as mine. Inside my TCC, there was charcoal caked onto a couple of the gears, another one had bad grooves. But I'd only driven my car for another 45 miles after the light kicked on, not an entire year.