Borg Warner problems

Hi,I would be very grateful for any advice on my V12 BW12 autobox problem.
Will only change from 2nd to 3rd if I floor the throttle and drops back to 2nd almost as soon as you ease off.
Checked fluid level and vacuum supply and all seems ok.
Cheers. SS

A good, complete flush of the tranny would be my first move.
Don’t know if yours has a transmission oil cooler, or not, but if it does flush that one too…

Hi Patrick, thanks for reply,have done the oil flush and has improved a little.Still needs high revs to change up though. Checked vacuum ,seems good at the box supply pipe.not sure what else to try.

The vacuum modulator could have a ruptured diaphragm.
Try removing it and sucking/blowing through it.
Rob

You can try sucking/blowing through it before removing it if you wish.