Will transmission failure do any additional damage to the engine?

The transmission on my 2005 Toyota Sienna minivan failed a few weeks ago with only 116,000 miles. I got two opinions, and both said the transmission failed and needed to be totally rebuilt. I took it to what I thought was a reputable national franchise, who had trouble rebuilding it but finally thought they had it right. After I had it back for less than 24 hours, the engine started revving and not shifting, and the check engine light was on. It was not drivable and had to be towed back to the transmission repair shop. The transmission is being re-built for the second time. My question is this: have these two transmission failures possibly done any additional damage to the engine? We have a 3 year warranty on the rebuilt transmission, but we drive this car a lot, and in harsh winter conditions, and I’m considering trading it in as soon as it’s fixed because it just won’t be dependable. I would prefer to keep the car for another 30-40,000 miles, but I’m concerned about its reliability and possible additional engine damage due to the transmission issues.

Transmission problems will not damage the engine one bit. In pulling the transmission and reinstalling it, something connected to the engine may have been installed improperly or not at all causing it to run poorly. So while a bad transmission will not hurt your engine, poor removal and installation of the transmission and surrounding components may.

I hope that reputable franchise was not SCAMMCO or you’ll keep going back and back and back. Sounded like the engine was just reving up from not being connected to a functioning transmission and the engine light probably was from the trans failure. Transman is the resident expert though.

I would only go to a dealer or an ATRA member trans shop now. I had mine done to save a couple hundred dollars. Seven weeks later I got it back, not functioning properly. Cost me another $300 to have the error fixed at another shop. Two year warrenty that was only as good as the shop. It failed in a year so ended up paying an ATRA shop to do it right the second time. On another car, the trans went out on the way to work. Towed it to an ATRA shop, and it was ready that afternoon with a rebuilt trans. I never missed a beat. Anybody can take them apart but it takes real training, skill, tools, and equipment to put them back together again.

Never go to a national chain because:

  1. No matter how simple the problem might have been to fix, they will always say “needs to be rebuilt.”
  2. When they rebuild it, they rarely get it right.

Water under the bridge at this point.

OP, does not inspire confidence taking it back but the likely case they will get it fixed. Best of luck.

Trading it in makes little sense except for confidence. You just spent $$$$ and should reclaim that in the next 30-50k of driving.