Shaking steering colum

I have a 1990 chevy conversion van. Recently I’ve noticed that as I reach the speed of 30 to 35 mph, the steering colum and steering wheel shake and vibrate badly. sometimes I even think I can feel the whole front end vibrating. This vibration seems to stop once I ease my speed past 40mph. What could be causing this. Someone I know mentioned that my tranny could be causing the problem. I don’t know. I am NOT machanically inclined what-so-ever. Can anyone take a guess at what might be causing this problem?

I would start with a wheel balance and alignment.

I would also suspect a broken tire belt or tread separation. Either of those will show up when they balance the tires.

Your transmission is not likely to be causing your front end shake. Lots of people think transmission problems cause anything from taillights not working to engine misfires, and they don’t. The most likely causes of this problem is a tire problem (broken/slipped belt, tread separation, etc) or loose front end components. I believe your van has two idler arms, and if they are worn out, which they probably are, they can cause the wheels to swing back and forth in any direction they want to go and cause just the symptoms you are experiencing. This can be a dangerous situation, so get it taken care of ASAP.

The speed is too slow for tires and wheels. Most tire and wheel related vibrations occur in the 50 to 70 mph range.

I suspect U joints or CV joints.