I have a 1997 XK8 that is slow to engage drive after backing up. It takes around 4 seconds to engage . From what I have read here that is a symptom of pressure regulator valve wear in the valve body, which in turn will take out the A drum. I found the Sonnax kit with reamer and oversized valve. Has anyone used this product and had good luck? Or is somewhere I can send the valve body to have it repaired? The transmission operates normal after the slow initial engagement.
Thanks for your time.

I'm no expert but have you had the oil changed or checked the levels yet? How many miles on the transmission? Are there any other symptoms like a whooshing noise? Does the car bump or slip at any time in any gear? These are questions the guys will need to know.

Contact sunbeltvalvebodies.com. They supply rebuilt bodies, but I don't know if they do retail. I considered buying valve kit, but mine was not exhibiting any problems, so I just replaced the main pressure valve with the ZF upgrade.