Just an overview.
The most prevalent code indicating you need a replacement transmission are concerned with mismatch of speeds. Often involved with 2 to 3 change flares (slip) of the clutches causes a mismatch. That if severe with throw a code and might even effect a limp mode or loss of drive
Equally there are some sprag (one way mechanical clutches) inside the running pack which can slip start to break up and these scatter metal inside the box. Now caution there are two types of metal; in layman terms I call them the
fuzzies and the
sparklies.
The
fuzzies are normal amounts of fine metal particles that are to be found in ANY auto transmission over time adhering to the donut shaped magnet in the pan, and to many a DIY'r this goop is alarming. Much of it can be removed in doing thorough a service and replacing the defunct donut with a new magnet one which these days is square and looks like 5 bar gate. Cost is about $10,00.
Problem is that if you extend to service period or totally neglect it, the
fuzzies also can adhere to the speed sensors located in the circuit board corrupting the speed signals and you can get similar fault codes. Some less than honest shops interpret the
fuzzies as severe metal contamination and that determines a replacement posture/claim, so beware!
The
Sparklies are something different! This is substantial metal particles shed off of components breaking up like a sprag clutch going south or teeth / bearing wear taking place.
Dropping the fluid and checking some in a glass jar will show if there are
sparklies in suspension. Dropping the pan and examining the suction filter and the pan floor will reveal metal in abundance if its going south.
A road test can often give you some indications. Luckily here in Golden I have the front range of the Divide to punish the transmission up some steep grades. If its about to go south it will protest and sometimes stop driving. Happened to me only last week! Customer complained of loss of drive when hot.
Had to get a Landrover to drag the lame beast back to the shop during an aborted test run!
With a scanner connected in data and with an assistant reading the outputs I get it hot then use the tiptronic to shift the gears "hard" through the speeds doing power shifts on a grade. If there is going to be a shift "flare" in the making it will show up on the up shift and you will feel the clutch pack or the sprag clutch slip and this will often result in a very jerky shift or total slip condition. On this 05' Tinny were were testing the blighter held for one circuit up the mountain but took a dump on the second run. We both exclaimed there she goes Capt'n
, "Bingo" found it!
Going down the grades I lost all speeds and opening the window I could hear the jingle bell rock tinkling away from underneath! There's the problem inside the running pack!
So first the unit needs a good interrogation with a scanner and a check on fluid/filter service history conditions before determining it needs a new box.
On this last case it did with 350K on it but one before with 175K needed a good service to make it run like new again.
To conclude
A good examination and service can be much cheaper than a replacement ,
Hope this has helped you,
Cheers Dennis