Recently purchased an E53. Have questions!

[srmmmm]

"Transmission:

As far as I can tell, mine has the A5S390R. Sometimes, the transmission exhibits hard up-shifts even with fairly restrained driving. Going from start to stop will kick like a mule about every 10th or 15th time. This also occurs at random gear shifts seemingly through the entire range; it's not always 1-2, or when I go from stop to start. Transmission temp seems to have no bearing on hard shifting.

More worrying - when I floor the pedal on the highway, it will very rarely rev up past redline and hold it for about a second before shifting. This has happened a few times since I've owned the car.

I've Googled these problems extensively but nothing concrete has presented itself.

1. People say there is an EGS firmware update. Could that solve the problem?
2. Service history shows no transmission service; could it just be old fluid/filter causing these problems?
3. Would I be taking a risk by draining it and replacing the fluid/filter at this point?"

Your vehicle has the GM 5L40E transmission. Considering the mileage on the unit, I would strongly recommend no fluid change. Instead, look into the firmware update. Mine was done in 2006 at 54,000 miles and I have not experienced any shifting issues at all.

I would recommend you inspect the front driveshaft splines going into the transfer case though. AC evaporator condensate dripping on the driveshaft, combined with inadequate lubrication from the factory caused rust and eventual spline failure on many E53s.

2002 X5 3.0 317,600 miles (Original transmission fluid, and yes, I tow)
2014 428i 26,000 miles

2004 325i sold at 123,600 miles
2001 325i sold at 66,000 miles

1970 Firebird Under restoration