automatic gearbox and clutch

Hi All,

Im a bit gutted today, my story beggins a few days ago when the clutch started slipping, so out of interest I checked the automatic transmission flui level and the dipstick was dry, so I topped it up until I could see fluid on the bottom of the stick with the engine switched off as it had started to warm up.

On the way home after topping things seemed to be better - HOWEVER, just been to gas up and it seems even worse than before.

I am planning on chenging the oil over the weekend (if this f***cking rain ever stops).

I don't really know anything about the automatic gearbox or how the clutch works on an automatic, can anyone give me a short explanation.

Thanks very much

John

theres more than one clutch ,usual one to go is clutch pack A but also C if free wheel is not locking instantly ,usually boxes can be repaired with the replacement of 1 clutch pack sometime 2 and sometimes free wheel clutch, a sign of faulty /burnt clutch pack is black burnt smelling oil , drive comes from engine through torque convertor where oil at high pressure is transfers torque/drive through one turbine to another ,the reason why not all power/revs are transferred like a mechanical clutch,t/c does have a lock up clutch in side it which at 50 mph ish gives direct drive bypassing t/c , box it self has 5 clutch packs although clutch c is 2 ,and through different combinations of clutchs locking different parts of epicylic gear sets gives different out put ratios,so one clutch doesnt operate one gear set as you might think like a manual where you have specific gear sets for each gear ,most boxes i see can be repaired for £200 -£300 but some are beyond economic repair

John,
Keeping it simple, an auto box has a series of "clutches" that brake and hold the gear selected, to transmit power. These are operated by internal hydraulics. The actual selection can be by vacuum or electronic or both. The fluid in the box lubricates the gears, operates the hydraulics and cools the whole shebang. If your fluid has been lost there are usually dire results. First step is always to change all of the fluid, drop the g-box "sump" to get it all and clean any mesh filters in there. Dont forget to check if a transmission cooler has been added, you will have to empty that as well. Follow the filling instructions. Once the box has fresh fluid it MAY recover. You may have to change the fluid a couple of times before it stays nice and fresh looking. That will have removed any crud, but you still may not have got away with it. The Clutches can burn without sufficient fluid and will then be cooked or at least out of adjustment. Any internal work on the auto box really is a job for a specialist, too many specialised tools, sterile conditions etc. OR you could always do what I have done, take a chance on a checked S/H box. It won't cost more than a few fluid refills and you will (hopefully) only have to do that once.

Thanks for the explanation, it always helps to understand how something works before you start attempting to fix what is wrong with it.

But good news, the issue was lack of fluid and my ignorence and neglect to the automatic transmission fluid level.

When I changed it I got 2 litres out and put about 8 litres in and it was a really dark rust colour, so ready for doing. In future the fluid will be regularly checked and changed every 12 months.

That should keep the old girl happy.

Thanks again for the help all.

John