Do I really need this $5300 transmission replacement?

[Valoru]

My car has 120k miles and after stopping at a red light, it felt like it started in 2nd or 3rd gear until 2k RPM, then slammed into 1st and showed a "Transmission Fault." The dealer charged $150 and quoted me $5300 for a new transmission, but they didn't explain why it's needed. I got codes P0729 and P0731 after they cleared them. Should I trust their diagnosis, or get a second opinion?

 

[Mclister Sue]

To be very honest, I'd recommend getting a second opinion, the codes suggest issues with gear ratios, but the dealer's quote is a whole lot without a clear explanation

 

[Magik]

The codes you got point to a gear ratio issue, but it might not necessarily mean a full transmission replacement is needed. It could be something like a solenoid or valve issue, which could be cheaper to fix, tale it to another shop

 

[ultim8escape]

My car has 120k miles and after stopping at a red light, it felt like it started in 2nd or 3rd gear until 2k RPM, then slammed into 1st and showed a "Transmission Fault." The dealer charged $150 and quoted me $5300 for a new transmission, but they didn't explain why it's needed. I got codes P0729 and P0731 after they cleared them. Should I trust their diagnosis, or get a second opinion?

In case they haven't convinced you.. get a second opinion before dropping that kind of money!
Try looking for an independent mechanic who specializes in transmissions.
They might be able to give you a more detailed diagnosis and hopefully other options that don't include a full replacement that costs that much!
It could be fixable for less!