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Matt
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 21865
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I own a 2015 Land rover Discovery with an eight speed gearbox

Customer Question

I own a 2015 Land rover Discovery with an eight speed gearbox - my problem is that vehicle changes down gears when cruising is extremely sensitive so that when following a vehicle on the freeway it tends to hunt gears if you try maintain a following distance - it also will change down a gear at speeds of 130 klms and very quickly revs past 3000 rpm forcing you to take over and manually change. It has now got to the point that if I cant drive this vehicle in speedo cruise at cruising - then I am are forced to drive the gearbox manually - I have driven a similar version of Discovery to compare and my vehicle cannot compare to the driving pleasure of the vehicle tested, to date the agents are unable to resolve this issue - but as a qualified Mechanic myself it feels as the response of the throttle pedal is to sensitive
Submitted: 1 year ago.
Category: Car
Expert:  Matt replied 1 year ago.
Hello there was a software update to the transmisson control early on so the 1st step I'd say is to contact your local dealer with the VIN to hand ans check if this update has been applied if this is up to date then I'd next check for an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for causing rough running. as the MAF sensor is the main load input it has a strong effect on the gearshift quality and control As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running. Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts. The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.
Expert:  Matt replied 1 year ago.
Hido you still need help?Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. I am only paid for my work on this question if you rate my answer, using the star system at the top of the screen. Please do not forget! Thank you