Keep an eye on your auto box!

[Ferret]

A few weeks back I started noticing some odd behaviour of the auto box - at flat out joining the motorway as it went through the top end of third gear it would start making funny slip-lock-slip-lock feelings as it was about to shift into the 4th and final gear. (4HP24)

With some help from Shogun, I discovered that this box isnt sealed and has an odd locking dipstick. Took her for a run today and let the box warm up, then checked the dipstick - which came back -at- the lower mark with the engine running.

The fluid is just starting to burn up, having gone a light yellow-brown colour when soaked up in white paper. I dont think the fluid's been changed from new :) time to do a partial change I think... though at 150k miles it could be risky...

What do you guys reckon? Drop the sump and change the fluid without flushing the torque convertor just to refresh the fluid?

Have topped off the gearbox with D3 Dexron, which was fun in the ice :)

Some nicely stained pink snow out there now!
http://i11.photobucket.com/albums/a190/Ferret101/850/IMG_0113-2.jpg

[shogun]

you have to check the transmission fluid temperature. There are 2 minimum levels in my dipstick like shown here.
Minimum at 40 degree c, minimum at 80 degree C and max at 80 degree C.
http://www.europeantransmissions.com/Bulletin/DTC.BMW/BMWtransService.pdf
I would remove the pan and add a new filter at the same time and in spring do the same and change fluid again. And maybe in summer a third time, then you have anout all the fluid changed.
But if the fluid starts getting dark and starts to smell burnt, a fluid change will most probably not help that much, but you will have to see, maybe the fluid is still o.k.

That as a starter, in spring check again the fluid.

[whiskychaser]

You probably know there are two schools of thought on the atf change:
a. Leave it alone cos only the crap is holding it together
b. Get it changed cos thats the logical thing to do.
I'm a great believer in letting the tranny tell you whats wrong - get the fault codes read. If you are stuck for an interface or its silly money down there pm me

[ArnZ!]

I reckon drop the auto sump, change filter, refill, then maybe another 10k kms later do it all again.

Doing a full flush maybe too risky, my dads 4x4 auto had very dark fluid, drove fine and everything, got his fluid flushed and luckily no problems. So sometimes it works, but sometimes can make it worse, everyone experience varies.

Good luck.

[Ross]

Change the fluid in the pan and the filter, do the fluid only until it's red again. Dexron is cheap and the old stuff ain't holding anything together*. If there is a lot of friction material in the pan start saving for an overhaul.
* Friction material in the fluid might help worn clutches to grab but this same friction material is also circulating through bearings, valve body and various other hard parts accelerating wear on those expensive components.

[genphreak]

I had this trouble with a 4HP22EH after the brake light/Cruise Control cutof failed to disengage. THe PO had probably been through a scary brake against Wide Open Throttle so maybe the top gear clutches were worn. I put in a new filter and switched to Castol synthetic at 230k. The whole tranny started working like a dream until the shaft seals finally wore out at 290k. Yea watch your levels scientifically, don't just top it off. It won't like having fluid at the wrong level at all.