Noisy Gearbox on 740 GLE Saloon

[PrinceWill]

My 1990 740GLE automatic transmission has started to become noisy.
It has done 228,000 miles over its 33 years. Its appearance is excellent, and it has given me reliable and comfortable service. It still does more than 31 mpg when travelling any distance.
What advice can you give me on the alternatives of investigating/rebuilding/replacing the gearbox or sadly disposing of the car?

[john.wigley]

Originally Posted by PrinceWill

My 1990 740GLE automatic transmission has started to become noisy.
It has done 228,000 miles over its 33 years. Its appearance is excellent, and it has given me reliable and comfortable service. It still does more than 31 mpg when travelling any distance.
What advice can you give me on the alternatives of investigating/rebuilding/replacing the gearbox or sadly disposing of the car?

Noise is but one symptom of a possible fault, 'P.W.'. What sort of noise is it? Knocking, grinding, squealing ... ? Is the ATF clean and a bright red, or is it dark brown and smell burnt? Does the 'box clunk, 'flare' or change gear smoothly? The more information that you can provide, the better people may be able to help you.

If the ATF hasn't been changed in a while that is where I would start - two or three partial changes are generally considered preferable to one complete change, which can itself give rise to issues in a well used 'box.

Regards, John.

[Forrest]

It’s worth trying to identify exactly which transmission your car has. There’s an article here that might help. If yours has the 16V engine note that the ratios may be different from the vast majority of similar transmissions out there.

https://en.wikipedia.org/wiki/Volvo_..._transmissions

It is not a major job to change the transmission. I had this done on a 940 years ago and was pleasantly surprised at the cost. Swapping the transmission would be DIYable at a pinch but is best left to someone with a proper car lift and transmission jack.

An automatic transmission specialist would have no problem rebuilding it for you as parts are readily available. That might give a better end result than a used exchange unit but is likely to take longer and cost more plus you would be without the car for longer.

[PrinceWill]

I checked the transmission fluid level today in accordance with the Haynes workshop manual.
As expected, it was filled to just below max and was clear and odourless. I have used the same garage for at least the last 10 years for servicing and have found them most reliable.
I can only describe the noise as a throaty roar which increases with engine revs. Originally, I thought it was the start of a leak on the exhaust, but this proved incorrect.
It was my engineer who diagnosed it as the transmission.
My concern is the cost of transmission rebuild, the percentage success rate of such a rebuild and the availability of any required replacement parts.
It may be better to sell it as is, in the hope that an enthusiast with skills that I do not possess, can fix it and enjoy its use.
I intend finding out what variant of transmission it has.
Once again thank you for your responses and suggestion.

[john.wigley]

Thanks for the update, 'P.W.', but are you absolutely certain that the noise is emanating from the transmission?

If all's well with the ATF, and in the absence of any other malfunction, e.g. slipping, rough changes, reluctance to change up, etc., I wonder if it might be something like a rough bearing in the drive-line for example?

Remember that sound and vibration can travel and may mislead you as to it's origin. Have your garage had the car in the air, ran a stethoscope over the 'box?

I had an auto box fail completely on my 745 on the M1 many years ago, but it wasn't noisy as such. Volsaa in Derby fitted a second-hand unit for me and the car ran well for many thousands of miles afterwards. If it is the 'box that is failing, and you like the car and it is otherwise in good condition, that is the way in which I would be inclined to go.

Regards, John.