I bought a used Chevy Silverado (5.3) almost a year ago, just after the great Harvey flood. It had 145K miles at that time. I checked the vehicle over pretty good when I bought it, and I remember seeing nice red Trans fluid on the dipstick then.

I have since driven about 15,000 miles, and I checked the fluid again this week and found the fluid level almost 2 inches above the crosshatch mark. I don't know how I missed the overfill earlier, but I suppose I did.

I took it to an independent shop and they did a BG flush, and the fluid is now new, and at the correct level. The truck has never exhibited any trans symptoms. Shifts have always been correct. The fluid was still red at the time of change.

My question is, all things considered, how much damage (if any) was done? Should I worry much? Thanks.

Was the trans at operating temp and the truck on a level surface when you checked it both times?

Yes. Its pancake flat here where I live.

I'd say that if no drivability concerns have manifested, you're probably fine.

Is it leaking in from the transfer case?

The problem with overfilling is that the ATF will get up into the gears and air bubbles will be created, then the air mixed with fluid will cause slippage. I doubt if 2 inches overfilled would cause any trouble at all.

Never had any leaks. No issues ever noticed.

Really to full and it would be blowing fluid out the breather. If that never happened, no big deal

Sorry, but I have to ask. Did you check the ATF with the engine running?

Yes.

If it's not broken don't fix it.

No damage.
Move on.

I think you'll be fine, besides, worrying about it isn't going to change a thing. Drive on.

+1 Probably nothing. It sounds like it was possibly filled to the full/Hot mark when cold. To move it up the stick that amount doesn't necessarily translate to a whole lot in the pan. I wouldn't loose any sleep over it.

In line with what Trav just said:

So much fuss was made over checking the fluid in my auto I got the bug to check it several times during a day of local driving whenever I did a drain & fill.

I'd be careful in the first place and have done a few D&F's over the years.

I'd always find level spots to park and follow the method.

The fluid's level would dance about all day long.
I concluded the key was to let the car be still THEN do the gear range row (P to L to P SLOWLY then check level within 20 seconds).

You maybe got a false level reading