computer-controlled transmission
 

OK, this is for the tranny experts. This morning, I heard a commercial for Aamco Transmission - a company that I assume knows their stuff about that. The commercial said that because of all the electronics in cars now, the wrong size tires or even an incorrectly installed car stereo could cause transmission problems. Is this true??? I mean, I know that the car's computer controls a lot in a car these days, but this just sounds like a bunch of propaganda to make suckers bring their cars in for a checkup. What do you think?

I don't think so...
Especially the tyre size... Bullshit.

Well I guess it could have an effect on the transmission, but only if the extremes of these scenarios are taken. Like moving from 8 inch tires, to 18 inchers, will cause extra stress because the transmission was not geared or designed for tires that big.
/non-mechanically inclined opinion

Ok the wiring stuff is definately wrong.....only if you wire it up so bad that you fry everything else electrical in the car and cause fires it will do it...but changing a radio won't do a thing.

I hate to say it, but in a VERY FEW number of cases they are correct. Think about high current power cable, when an amp is drawing alot of current, It creates a magnetic field around that power cable. And as we all know magnetic fields can do all kinds to computers.

I have heard many stories about mobile phones setting of airbags. I guess that It maybe the same sort of thing.

They are correct. Tire sizes CAN really mess with the computer and the transmission. In an extreme case, add-on electrical components, including amps & radios can cause this as well.

Listen to DE137. New technology has wireless feed from the trans to the speedometer. Unshielded wiring can mess with the signal. Tapping into the wrong circuit for power could affect voltage readings to the ecm for the system you tapped.
Also, sensors read driveshaft revs for input into the ecm. A change in tire diameter (do you love those new 22" rims?) skews the math. The vehicle is not going the speed it thinks it is, the shift points get out of whack. Data from the ABS sensors and the vehilcle speed sensors don't agree, the ecm gets confused and pops a trouble code.
Shortly after that, Peter Sellers rolls into the room in a wheelchair and and salutes, "Sieg Hiel!" (;-))

On some new models like Chrysler products you need to flash the Trans computer the tire size so it reads tire revs correctly.

Plus everyone was on the money with the electro magnetic fields created by high energy amps and such.

Be careful where you route those wires.

I hate to say it, but that's an urban legend...
And a mobile phone cannot light up a petrol station station either. Somwhere I saw a calculation how many mobile phones needed to create a spark (to light up something). The number was well over 1000...

Id on't remember the details, but I believe there's a way you can fuck up an auto transmission's computer by improperly grounding your amps.

Changing tire size can make for poorly timed shifts, and inaccurate speedo readings. The radio has me stumped a little. On all newer GM cars the radio has a serial data link to all the other modules in the vehicle, and on some cars functions like tire pressure monitors, oil life reset, and some personalization features are controlled through the radio. I don't know how other manufacturers do it, but I could see it happen.