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Ross, Diagnostic and repair technician
Category: Car
Satisfied Customers: 1183
Experience:  Licensed diagnostic and repair technician
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. I have just purchased a 2002 Bentley Arnage T. The auto

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Hi. I have just purchased a 2002 Bentley Arnage T. The auto gear change has a "take-up" whine between 1st and 2nd gear (only), which I am told by my Rolls Royce/Bentley garage is "perfectly normal, all Arnages do this".
That doesn't sound right to me. Can you please advise.
Many thanks.
Ross :

Hello and thanks for trusting me to help you today. I am a licensed diagnostic and repair technician, I look forward to working with you.

Ross :

Is this a loud whine which could be described as a grinding noise on deceleration or a distant whine which clears on deceleration?

Customer: Hi Ross. Thanks for your help. It is background but clearly audible whine on acceleration from 1st to 2nd gear. After that all functions normally with no inordinate transmission whine. ? M.
Ross :

This does actually sound normal for these transmissions. Bearing noise will make a grinding noise which changes between acceleration and deceleration so I'm confident there are no such issues with bearings. The whine you hear from 1st to 2nd is caused by the shape of the gear teeth. Helical cut gears are used on most gearboxes (Cut at an angle) This gives a much quieter gearbox, however helical cut gears compromise on strength of the teeth. Straight cut gears are very loud due to the meshing angle of the teeth, however they are very strong in comparison.

The first gear set on your transmission uses helical cut gears as per all of the other gears, but due to the high loads on the first gear set and large amount of torque, as well as getting more use from pulling away etc. they have been cut at a slightly straighter angle which gives a much stronger first gear. Unfortunately as with most things mechanical, It is a compromise between refinement and strength, Bentley have got the balance as good as they can with the noise to strength ratio offering a very strong gearbox but this does naturally cause more noise.

Ross :

The more use the gearbox gets it is normal for this noise to very gradually become more prominent due to the natural wear on the teeth, comparing one for e.g with 100k miles to a new one you would notice a difference, however this is also completely normal due to the natural wear of the meshing surfaces of the teeth. Another contributing factor is the quality of transmission oil. If the oil has degraded it can cause more noise, so regular servicing when required is important but these are all things that make a "normal" sound more audible rather than causing a problem.

Customer: Thank you Ross. A very comprehensive answer. I will have to live with it, it seems.
Customer: Is there an oil additive to assist this problem, like you would use Werth for engines?
Ross :

There are additives, but with an Auto box like this, I would be inclined to avoid them where possible and opt for a good quality oil change instead (if its not been done for a while) Otherwise Lucas sell an additive for gearboxes which will help reduce meshing noise of the gears. If you are to add this, i recommend an oil change at the same time

Customer: Again, thank you Ross.
Customer: Very helpful.
Customer: all the best
Customer: Mike
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