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BN2 gearbox working unredictable

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M

musme

Senior Member
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Some time ago my BN2 gearbox began to do some very strange things. sometimes when I would put reverse the car would not move as if it was in neutral. Then suddenly it would engage but with very little power and the car would barely move in reverse and then suddenly it would start working correctly and this has happened many times.

On another ocasion I tried to start the engine by engaging second gear and I could put first gear, second, third or fourth and the gearbox  would not engage as if the car was in neutral and I was not able to start the car without the starter... Suddenly after 400 meters downhill the gearbox started to work normally.

Today I left the car downhill in first gear and suddenly the car started to move downhill as if t was in neutral. Fortunetly the damage was minimal, but when I checked the car was engaged in first but acting as being in neutral. Then suddenly the gearbox worked as normal.

I am totally confused. I had never heard this story before. I do not know what is going on....

1. Is it the gearbox
2. Is it the overdrive
3. The rear axle
4 the clutch
5 the pressure plate.

Please help !

Jose
 
Sounds like a typical overdrive problem. I could be wrong, but that's where I'd look first. PJ
 
This is absolutely the classic case of the overdrive hydraulics not disengaging. Check first by removing the gearbox cover to gain access to the top of the overdrive unit. Unscrew and remove the 7/16" hex cap of the screwed plug for the plunger valve. This is located on top of the overdrive and toward the right. With this cap removed, and using a small magnet, extract the spring, plunger and ball, and finally the operating valve which is a long thin round stem about 3 1/2" long. There is a tiny hole in the lower side of this valve stem that relieves hydraulic oil pressure when the overdrive is switched off. This valve and the tiny hole have been known to become plugged with debris and cannot relieve and drain back. Carefully clean this operating valve and make sure the little hole is clear and you can blow through it. Now simply reinstall everything and try driving the car. As long as you haven't destroyed the unidirectional clutch assembly inside the overdrive, everything should work correctly.
 
Do NOT even ATTEMPT to operate the car in REVERSE until you have checked the above and everything is working properly. You can RUIN the overdrive assembly in a BIG way. I know.
 
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