Hi there First thing is this the 4 or 5 speed changing fluid and filter on 4 speed is easy as sump can be removed and filter changed, on the 5 speed you cannot change filter without G/box removal, on both boxes you will not be able to remove all the fluid because of design so to do a good change you need to change fluid 2 or 3 times with a drive between changes the colour of the fluid is a good indication as to the condition of the fluid it should be a cherry red colour. This is all against what Fords say the fluid is in there for life. I take that to mean 300rpm rise with no increase in speed Have you had the car long or just bought it with this fault I think I would be inclined to do a fluid level check first you will also see the colour of fluid also. There is a set procedure for checking fluid level/draining in the FAQ section Hope thats of help to you ;) hi chrispb - firstly thanks for replying to my post - much appreciated. i bought the car last november and it has had the fault the whole time, never getting any better or any worse. yes, correct, the revs increase but the speed doesnt. i did read the info on here regarding the procedure for checking the oil level, and have spoken to frauds who did say that the box is sealed for life, which seems a lame approach to me. i will attempt the oil level check this weekend but think it may be an idea to buy a replacement filler tube/dipstick thingy part first as i have read that people have had them snap off when removing to check, i assume this relates to my gearbox which is the ag4 type (4 speed), and the sump is accessible for removal. i wondered if removing the sump to change the oil may be a simpler option, at least for the first change if there are filters to change aswell so as to do it all at once. i have spoken to a couple of auto specialists today who both seem to think it could be either electrical or mechanical failure rather than an oil issue, however i have also heard that sludgy oil causes problems and i can hardly expect mine to be rosy red after doing 110k miles!! ;) thanks again for the info. rich.