How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Matt Your Own Question
Matt
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 21969
Experience:  BEng hons Mech engineering, in auto industry 22 years
12772297
Type Your Car Question Here...
Matt is online now

Why does my 53 rev audi a4 automatic 2.5 diesel loose power

Customer Question

Why does my 53 rev audi a4 automatic 2.5 diesel loose power on the motorway + revs very high then nearly causes a vehicle to go into the back of me....I'm very worried as I have the Kids in the car with me???
Submitted: 3 years ago.
Category: Car
Expert:  Matt replied 3 years ago.
Hello

I'd take a look at the colour of the transmission oil it should be a dark red colour if its black then its needs changing together with its oil filter. Also check its level with the gearbox warm and just after you've moved the selector through all the positions leaving it for a few seconds in each one and then back to park.

You can top up the box through the side fill plug if required and make sure you use the correct oil for your car as the fluids are not all the same. Some manufacturers recommended a change of the type of fluid - Speak to the local dealer and parts dept - they will advise you on the updated fluid to use..

If that’s all OK then check all the electrical connections of the gearbox, remove each connector in turn and spray with contact cleaner. Check that the wiring to the gearbox is in good condition with no chafing or frayed wire

If this is OK then check the selector lever linkage / cable under the car for any broken parts and or missing bolts as if this is coming adrift then it can rub on the car body or just bind up

Then - you should top up if low and re try it - or, if its level is ok - and condition is ok - then the next step is to drain it off - open it up and clean the filters inside -- refill and retry it..
Customer: replied 3 years ago.

I've had the car on a snap on scanner + this has diagnosed the input speed sensor can this if not right cause these problems many Thanks


 

Expert:  Matt replied 3 years ago.
Hello Mark

A faulty gearbox speed sensor could cause missed shifts and can also it to lose drive as you describe

however to replace it the sump has to come off the gearbox to access the circuit board / with the integral speed sensor and while the sump is off have the garage also clean out the filter screen and refresh the oil