Automatic gear box transmission failure

Guest · Mar 29, 2008

Just a quick note to see if there is anyone else out their that has experienced anything similar to this. Picked up my first 928 S2 (childhood dream) last Friday in Arbroath. Everything appeard good regards engine bodywork etc. The dissapointment occoured on the trip back to London when after 200 miles the transmission failed as I attempted to accelerate after hitting traffic on the M6 arount Knutsford. I limped into Knutsford Service Station & re-started the car & the automatic gearbox (4 speed) apperaed to be functioning correctly again so I pushed on, only to have transmission failure again 10 miles south (engine reves but absolute pitiful power via the auto box). I limped into Sandbach & the AA were called. They checked the ATF fluid level with Nutral selected & engine in idle & this was ok . Their diagnosis was put it on a relay truck back to London. So its now in a Automatic Transmission Garage awiting its slot on the ramp. Initial discussions with the garage owner have indicated that it could be a desintegrating clutch plate causing the filter to progressivly block up. He said that once the sump has been removed & an inspection of the fluid can be conducted he will be able to verify this as a disintegrating clutch plate looks like tea leaves in the fluid. I'm no expert at all regarding automatic gearboxes & would value anyone elses experience of similar failures.

Thanks - Ken.

Brett928S2 · Apr 7, 2008

Hi KEN

Let us know how this goes....I still think its more likely a low fluid problem than the box (as I said in the email)....

But we will see when they have tried it...

All the best Brett

peanut · Apr 27, 2008

welcome to the forums ken.
Congrats on your purchase and commiseration on your problems.
I have a very rare troubleshooting diagnostic manual for these 928 Mercedes gearboxes. If you describe the symptoms exactly I'll check out the book.

If the car has stood any time unused or little used the first thing I would recommend is an oil change and renew the filters. Don't be talked into anything major before you have tried this.
Its essential to get the gear level absolutly spot on so the car has to be completly level when checking .
I'm betting its just dirty filter and gungy oil .If anything had failed it probably wouldn't have functioned at all.

just checked the book and it suggests
1. low fluid,
2 dirty fluid
3. clogged or blocked filter
4.mechanical break power train between engine and transmission.
we know its not 4 so if it is effecting all drives then it has to be 1-3 or all of them.

Guest · May 18, 2008

Penuts thanks for the advice unfortunatly too late garage expences paid for in full, Gearbox in & out £350 & gearbox overhaul £850 plus the dreaded VAT. Took the car to have its cam belt replaced by JM Garage an indipendant Porsche Garage in Christchurch. Bit of a treck from London but well wort it friendly expereinced staff working efficiently with all the right gear & a reasonoble labour rate. Well worth a visit, next visit the aim is to rid the car of electical gremlins. Oh & by the way JM Garage is 100 mtrs from Christchurch railway station straight back to London.