Quote:
Originally Posted by Volvoluke
Been changing it at least once a year. Using the simple sump plug drain method
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Try a slightly different method Luke :
https://www.ebay.co.uk/itm/Electric-...K/174146415941
Back the car up on some ramps so the back end is higher than the front, switch off and remove the trans dipstick. Use that pump above, wiggle the suction tube (thin one) down as far as it will go and arrange the discharge tube into an empty screenwash 5L (because it's clear) container, switch on the pump and go and have a coffee or whatever.
Come back about 20 minutes later and you should be near the end of the emptying process.
When the pump starts scavenging, switch off, remove the suction tube and the discharge container and put the lid on. Leave it somewhere to settle. Judge the amount of ATF that is in the container and put slightly less than this back in via the dipstick tube as you normally would.
Drive/roll the car off the ramps so it's level again and check, the level, topping up to the COLD mark on the dipstick if needed.
Take the car for at least a 5 mile run and then recheck the level, topping up to the HOT mark if needed.
Repeat monthly at least twice until the fluid remainsas clean s it went in, then repeat once a year to maintain it.
This will give you a good base to start from removing almost all the old fluid that is still contaminating the fresh fluid when you change it once a year.
I suspect that as you've only been doing a part-change yearly without doing a series of part-changes first you've really just been maintaining the old fluid at a slightly better level each time, rather than improving it. Now i'd take an educated guess that the fluid has got thinner and the torque converter is making the humming noise.
Also by getting the back end of the car in the air, all the sediment and contaminants will flow to the front of the box, where the dipstick is. Using the pump will remove the majority of these leaving the way clear for the fresh fluid to stay clean and fresh. It will also remove any water/condensation that may be present in the box which can also cause cavitation. In minor cases, cavitation could be described as a hum, worse cases are difficult to describe other than as a "squelchy hum".
Doing it this way helps to clear the mesh of contaminants as well so if your theory is right, this will improve matters as well. Either way, it will give much fresher fluid to start a diagnostic process from.
Many gearbox sump pans have a recessed drain plug (obviously to protect it) so old fluid and contaminants will settle around the recess and never be drained out using the simple sump-dump method. Using the pump method gets round this and an added bonus is that it's a lot easier on your back!
