So the gearbox fried on my 1997 XK8, mechanic told me it needed to be replaced. I didn't have the cash for a rebuilt one so I bought a used one and had it professionally installed.

It worked well to start but I noticed when I shifted from reverse to drive without fully stopping, I got the dreaded transmission fault. Turning the car off and then on again returned it to normal the first time, but the second time I had to let the car sit for a few days before it decided to magically work again. It took about three times for me to realize the bad shift was what triggered it so I was careful when shifting from then on out.

However, yesterday it faulted twice: once when I was driving normally in city traffic, and then again when stopped at idle in a parking lot. I'm worried that this used transmission that has been in for 9 months with less than 1000 miles is going to go up again.

So, any ideas? I'll add that I also had the car in to diagnose some strange whines and they suggested it was likely coming from the transmission.

HELP! I love my car but it's frustrating to constantly worry it's going to die on me.

 

What is the voltage across the battery terminals with the ignition in the OFF position for at least ten minutes?