Overdrive works 'Backwards.

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sdiddy68
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Joined: Sat Nov 18, 2017 11:21 am

Overdrive works 'Backwards.

Post by sdiddy68 » Sat Aug 25, 2018 8:52 am

Hi there, I have a late 1996 318is (M44 Auto). The 'overdrive' (lock-up torque converter) seems to work backwards. When I drive on the motorway I sit at 3000 RPM @ 60 MPH (100Km/h). If I go up a gentle rise the revs drop back to around 2750 RPM. The engine sounds much happier at these revs. As soon as I level out the revs scoot up to 3000 again. This is on the same stretch of road and I don't move the accelerator at all. I would expect it to work the other way round ie. drop out of 'overdrive (actually lock-up torque converter) and pick up some revs) going up the hill - then dropping back once on the flat again.

Otherwise the car is running perfectly. I bought it with the dreaded blown head gasket but I had the head machined and used new gaskets / bolts ...etc in the rebuild.

Perhaps a vacuum pipe id connected backwards. Perhaps the auto transmission control unit is playing up. Does anyone know what signal tells the converter to lock up? Is it a vacuum sensor? Perhaps the MAF? It's driving me nuts and I can't find anyone who's had the same problem. Trying the box in 'Sport' mode is the same.

Has anyone seen this before? It's a mystery.

Cheers. Simon.

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