Hello all!

thanks for having a look,

I recently purchased a 1999 XK8 at auction.
it had The dreaded cracked valve body problem with the transmission. It was clunking when accelerating. This has since been fixed but now after replacing the valve body, the car slips into neutral at about 20 miles an hour. All I have to do is then wait for it to reengage and it does. The codes are: PO734 PO1797 P1642

any insight anyone can provide is incredibly helpful!!

Thank you for having a look,
-Andrew

 

Hi Andrew and welcome to the forum.

A cracked valve body is often associated with other issues:- 'A' drum failure and/or main pressure regulator valve problems.

P0734 'Gear control malfunction – 4th' can relate to the output speed sensor which is disturbed during the VB replacement. P01642 and P1797 are CANBUS errors which may or may not be relevant.

Can you give us some more detail on what work was done?
"the car slips into neutral at about 20 miles an hour" Does this mean that you lose drive?

This could be as simple as low trans fluid level.

 

hi! Thanks for the welcome.

when the car was purchased it wasn’t slipping at all. It would clunk when accelerating from a dead stop.

the upper valve housing was cracked (see photo) this was replaced and the transmission was reassembled with the correct fluid level.

now the car slips out of drive at about 25 MPH. I will wait for it to reengage (while moving in neutral) (think if it was a manual having the clutch depressed). After it reengages after a few seconds it will shift perfectly. With very quick and smooth shifts. It seems to be a second gear problem. (I think?)



thanks!!!!