A friend of mine has an automatic gearbox fault on his 1990 BMW 520.
When put into DRIVE, it will go only about 50 yards before the transmission disconnects and the engine revs freely. If he then selects REVERSE the car refuses to move ……until the front end is bounced up and down a few times! It will then reverse normally.
Any suggestions will be appreciated.
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I think it will have the 4HP22E box, which I don't much care for - they are not very reliable.
However, check the simple things first.
Check the fluid level and colour (see if its burned, indicating clutch/band failure)
Check the cable/switch adjustment (if you remove the gear selector surround you will find a multiway selector switch that sends gearstick position information to the ECU). Clean the switch contacts with electrical cleaner and check the positional adjustment of the shift lever. You will need a Haynes manual or similar to guide you if not familiar with such things.
If the above fails to effect a cure then your next stop should be an autotrans specialist.
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When was the autobox filter and transmission fluid last changed? New fluid and filter can sometimes work wonders.
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I agree with Aprilia, especially about checking the fluid level first. Just make sure he checks it in the proper manner.
Especially important is to check the level with engine still running. If checked with the engine at rest the level will look OK but it will drop below 'minimum' when under way.
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Aprilia, could you confirm that *all* auto boxes need the engine running when the fluid level is checked?
I always make this assumption because all the boxes I have come across have worked that way. I just have this slight concern that there might be the odd exception.
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The only one I am aware of that doesn't is the old AP01 'box used on Austin/Morris cars of days gone by (e.g. the old Metro and Mini auto's). You used to warm them up and then turn off, wait 1 minute and check. You'd be lucky to find one now.
All modern boxes I've come across generally say 80 deg fluid temp; idling for a minute or two; selector lever moved through all positions. Check level.
Don't rev. early BMW/ZF 4HP22 'boxes whilst in Park - burns out the front clutch due to a design fault. Later 'boxes (after about 1993) were modified. Something to mention to MoT man when he does the emissions test.
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Some Honda autos are checked with the engine off.
If I remember correctly, early 4HP22 boxes can be revved in park, as long as the engine is started in park, and then revved in park, without shifting through drive first. Something to do with pressure applied to the clutch in drive isn't released when shifter moved to park, but switching off relieves the pressure.
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Some Honda autos are checked with the engine off. If I remember correctly, early 4HP22 boxes can be revved in park, as long as the engine is started in park, and then revved in park, without shifting through drive first. Something to do with pressure applied to the clutch in drive isn't released when shifter moved to park, but switching off relieves the pressure.
Yes, that's right. You have to switch off, leave it a few minutes and then start it up again. Problem is due to lack of fluid drain route in front clutch.
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