carl0s

Hi.
I have what feels like backlash in my 545i auto.

When I am on/off the power at gentle power levels, or even when it is just the box changing or dropping from connected to less-connected gear (i.e. cruising to a halt.. the box drops into a high gear, just like dumping the clutch in a manual and disengaging the transmission), well, I hear/feel a very slight ker-chunk of gears. It reminds me of my ls2/t56 rx7 - which I was used to it in.. but never in an auto.

I have new engine mounts to try fitting this weekend, but I have just realised that I am probably totally barking up the wrong tree.. If it was engine mounts, it'd be a dull rubbery thud wouldn't it, not a gear-engagement like lightly-affected kerchunk that I'm hearing?

My fear is that it's the gearbox. I bought the gearbox off eBay. It was apparently rebuilt by a gearbox specialist for £2,000, but who knows if they've done a proper job.

It could be a worn diff, but it sort of feels like the front of the car..

Anybody with similar experiences? I'm kind of beginning to think I should cancel my plans to swap the engine mounts tomorrow..

It's very slight, but I have a way of tuning-in to these things once I become aware of them. Some call it OCDism... I call it just wanting to have things right!

carl0s

I think, once I have dealt with the more important jobs of finishing the gas/lpg conversion, and replacing coolant hoses, I will dismantle the 6hp26 gearbox that came off the car (the old gearbox), and really take my time - checking all the tolerances etc, and replacing the solenoids (most likely failure point of the failed gearbox) , and swap the box.. see if this backlash changes. The gearbox seems to do everything perfectly, except that I have felt a rough 4>3,( or 5>4.. unsure.. anyway, a down-shift) while giving WOT on the highway/motorway.

ncsugrad2006

I have the full ZF rebuild manual somewhere if you need.. it's very detailed on how to measure all tolerances, etc.

carl0s

Yes please that would be useful if I do pull my spare box apart!

Thanks.

chrism24

Its just a software update you need (they fit a 6spd box in a 5spd casing and used smaller clutch packs so they wore faster and you need an update to fix it)

ncsugrad2006

http://www.bimmerfest.com/forums/att...2&d=1390184187 (file 1, page 1 to 52)
http://www.bimmerfest.com/forums/att...3&d=1390184187 (file 2, page 53 to 78)
http://www.bimmerfest.com/forums/att...4&d=1390184187 (file 3, page 79 to 104)