SD1 Autobox complete fail.

Junkman

Junkman

Member
A friend of mine is having bother with the gearbox on his SD1.
Previously it's been okay but occasionaly it would stick in first, then after 500 yards or so normal service would resume.
Then, after taking it down the road it conked out on the way home. He found a fault with a wire to the coil and after some soldering it finally got going.

He managed to get a filter and gasket from the US of A. He changed it and then went off on holiday for a few days. After he came back, he checked the level of the oil, started the car - and absolutely nothing. Not a sausage. No drive at all in reverse or any forward gears. He jacked it up on the diff and in reverse it spins a bit but in any forward gear the wheel twitches, but nothing more happens.

So, basically has anyone ideas on anything we could do, or check, or do you recon it's toast?
 
Junkman said:
GM TH180 if I'm not mistaken.
Click to expand...

If you're sure that the fluid level is correct(checking when hot and going through all the gears several times)the problem could be with the vacuum modulator valve. Check that the pipe that goes from the inlet manifold to valve is not split or broken in any way. If so, you will only be able to get up to 2nd gear by manual selection, and top gear when at around 90mph or thereabouts.

The vacuum modulator valve itself can fail, usually resulting in gearbox fluid being sucked into the inlet manifold, and then being drawn into the combustion chanber etc.
 
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