I am starting this thread because the sealed for life aspect of transmissions is being mentioned in both the Citroen C5 and Renault Laguna examples. I think that the issue should be examined in depth.
I don't want to open up the discussion to the 4speed transmissions, which, I think, are well documented.
I will use my cars as an example of my concerns. Both have sealed for life gearboxes.
Firstly, my Peugeot 406 SV had a 5 speed manual gearbox. When I had it serviced by a different mechanic, he drained the box at 215,000km and said that the oil was disgusting and very gluggy and amongst the worst examples he had seen. The change of oil noticeably improved the shift into and out of second gear in particular.
The Pug was replaced by a 2007 Citroen C5 2.2litre turbo diesel. It has a 6 speed auto gearbox and 110,000kms on the odo. It too is sealed for life, but I was quoted $220 per litre for the special Citroen oil. I understand that this auto-trans is used in other brands where the price of oil is significantly cheaper than Citroen fluid.
So, should sealed for life units be serviced with new fluids. If yes, where should fluids be sourced?
Thank-you for your thoughts. I hope that the thread becomes practical advice to me and you.