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I have a 2007 Chevy express van 3500 with a shaking problem in the front end under braking.  It doesn't do it all the time.  I'll stop 20 times a day and it will be smooth, then the next time it will try to shake the steering wheel out of my hands.  it doesn't pull to either side, it just shakes with a variable amount of severity.  It has new tires and an alignment within the last 5000 miles, and yes it was doing this b4 the tires.  We have checked the brakes and they look good, not warped.  Nothing obvious in the steering linkage, shocks, etc.  Has anyone heard of this before.  Does anyone know where to start.  Would a steering dampner help?  Also note:  this van is pretty loaded down but not over the gvw for the veh.  Don't know if that is pertinant or not so I put it in.  

look under the front... and see if there is a steering damper...

a steering damper is a shock absorber that keeps oscillations from gaining with each input.. some cars and trucks have them..

i also want to know if the antilock brake lights on the dash board light up...

how much play is there in the steering wheel when you have the engine running... with drivers window down.. and reach through to the steering wheel...  .. with the wheels straight forward..  work the wheel back and forth while watching the front tires..

see how much movement you have to input before the wheels respond..   if you have more than a half an inch or so with the engine running..   you may need to have the steering box adjusted..  by a professional wheel alignment mechanic.. over the age of 40.. or so..  not some kid at a chain tire dealer.. find a specialist shop that only does wheel alignment .. or frame repairs...   or even a truck and van repair shop..  

There is no steering dampner.  My mechanic an I were wondering about installing an aftermarket one as a fix.

The antilock light does not light up when this happens.  I'll check the play in the steering box and post the results.

thanks  

I checked the play in the steering wheel, I have to input 3/4 to 1 inch before the wheels start to show movement.  If the problem was in the steering box wouldn't it show itself at times other than when I am braking?  The shaking only happens when I am braking... and only some of the time.  

wobbles are hard to pin down...

it could also be the brake rotors that are warped...  and/or the caliper slides that are seizing... but these would show up every time..

i would really talk to an alignment tech over the age of 40... have him adjust your steering box if it needs it... sounds like it just might..

it could also be worn steering linkages.. worn ball joints... toe in out of spec...

wobbles almost always start small and get larger and larger...

i drove my 76 E250 ford van today... the steering box needs some help... i just had not gotten to it..  yea i know...  but it had the wobbles for the first time...   so tomorrow morning.. i dig out the Hex driver sockets. and the crow foot flair nut wrenches and my long extensions... with the wheels pointing straight ahead... i plan on using the crowfoot line wrench on the end of a long extension and loosen the locknut on the top of the steering box... the hex bit socket will already be installed in the stud and that also on a long extension with a TEE handle on it..   so i can turn it clockwise a few degrees while holding the jam nut inplace and with my third hand.. wobbling the steering wheel to see just how much slack i can remove without going too far and creating a binding problems...      remember... you are changing the clearance between tapered gears... taking out the clearance.. but not all the clearance...  go too tight... and the box will bind..     it really takes a touch... that years of working on cars can get you...