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Discussion Starter #1
Hi. i have recently bought an 1990 850 auto and it has been wonderful up until this morning. as i was driving to work, under acceleration, it seems like it slips out of gear, like a slipping clutch on a Manuel car. as you squeeze on the throttle it will accelerate until the torque seems to much and then the rpm kicks up massively. its like it is not in gear but it still accelerates but at a slower rate. i have no idea about autos. a friend said it could be a torque coupling mounted on the rear wheels. im rather worried that i have broke it big time and that it may be expensive to fix. do these cars have one? please help......:confused
 

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don't listen to your friend.

do the easy stuff first, check oil levels.
rub the oil between your fingers, is it gritty, does it smell burnt, is it black.
what gear does it do this in?
how many miles has the car done?

my initial thoughts are worn out friction plates in the gearbox which will mean an expensive re-build.

check the oil, if black, take to an auto transmission specialist.

(but could be a host of other things.)

p.s. welcome to the forum and the proper E31.
 

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Discussion Starter #3
thanks for the tips. i haven't check the fluid levels yet as it started doing it suddenly this morning. its done 130k miles and it slips in all gears. i shall try and check the fluid levels when i get home. im assuming that i have to jack up the car level and let it run for a bit?
cheers, A
 

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Discussion Starter #4
i have just check the transmission fluid. the level is good, its a brown-ish colour and doesn't smell burnt. it didn't feel gritty when i rubbed it between my fingers.
i took it for another spin about the bloke and the problem has not magically rectified itself which is a shame. even with out the tcs on and in manual mode the same thing happens. but in reverse it hold torque fine and spins the wheels.
does this model have a separate clutch for the reverse gear at all.
if it needs a rebuild, then a second hand gear box maybe cheaper.
A
 

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Reverse uses more pressure in the clutches and is lower geared than 1st. so won't slip.

probably best to take to a specialist and get it tested.

check the levels when up to temperature putting in P with the engine running and using the dipstick.
a second hand box may be cheaper but you could be buying the same problem. get the box out of a car that you have driven is the best or that you know the history of.
the picture (if you can zoom) is the pressure test proceedure.

could be a pressure regulator issue, the clutches are not getting enough pressure to hold the torque. drive careful and steady until you get this properly diagnosed.

Also has it been steadily getting worse? or all of a sudden?

hope it works out for you.
 

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Discussion Starter #6
thanks very much. ill give that a go. also my power steering pump is leaking, and i wonder if it connected to the pressure for the clutch? ive been topping it up just for pottering about as i know its connected to the brakes.
 

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thanks for the advise. is there any way for servicing this valve at home rather then taking it to a dealer? or is a horrible job that requires a bit more than a Haynes manual (which i have to buy)?
 

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you need to take it to a specialist first. Diagnosis over a forum is never 100%. I've posed a technical manual thread on here, that's all you need for now. You can do this at home but will be a right bugger of a job on axle stands.
Take it to a specialist first. Then another to get a second opinion, because the first one will want to charge £4k for a rebuild.
 

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On Neil's electrics suggestion, I fixed a gearbox fault (the dreaded TFS that wouldn't go away) by removing the EGS (gearbox control unit, in the boot on driver's side) and putting it in the airing cupboard overnight. It might sound mad, but it's super easy and giving it a nice warm bed for the night gives it a really good reset!
 

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Discussion Starter #14
thanks. ill tray both of those. the car has been damp inside in the past. sometimes its like a rain forest inside in the morning. and various things do bong at you when driving but seem to find no real problem.
when disconnecting the batteries, do i have to save any passwords or anything other than the radio. the alarm will not pack up?
A
 

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You don't need a Hayes, you need to original repair manual, which is widely available on the web. If you pm me with an email address I'll be happy to send you a copy.

You need a set of manometers and associated connection gear to allow you to measure internal oil pressures in the gear box - the manual explains how. Whatever you do, do not keep driving the car. Once they slip clutches wear out very quickly. Once you have measured pressures you can draw conclusions. It could be something simple like dirt in a valve preventing it from sealing completely to allow oil pressure to build up behind it.

Most people are afraid of servicing and overhauling automatic transmissions. In actual fact they are easier to rebuild than manual ones because everything basically sits on one shaft. They do contain some very strong springs so you need a bit of equipment, notably some sort of bench press. Sometimes you need to produce a special tool of some sort but if you have steel and heat this should not pose a real problem. You also need a bit of measuring gear because distances within an auto box are measured with tolerances of hundreds of millimeters. It is good to be able to measure both internal and external diameters with micrometer accuracy to check for wear in valve bodies.

Apart from that, refurbishing auto boxes (and modifying them to race performance) is pretty good fun.
 

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"Don't shut the boot (you won't get back in it)"

Lol, Neil. You can open the boot manually by inserting a key, pushing it in and turning...

Don't scare off the poor chap :).
 

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"Don't shut the boot (you won't get back in it)"

Lol, Neil. You can open the boot manually by inserting a key, pushing it in and turning...

Don't scare off the poor chap :).
not on mine taly!!!!!!! and the route in from the ski hole is blocked by a huge gas tank!!! but yes, don't forget the key :embarrassed
 
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