I was asked the question of what could cause steering wheel kick in a vehicle that had TC and a Rear TT. (not a landie) the symptom was described as the kick I had shown in fozzy when demonstrating some of the effects of transmission wind up but faster. (a fairly inexperienced but keen guy and the vehicle is as he purchased it)
I initially suggested that it was something damaged in the front end. That confirmed his thoughts so the front end was stripped but the investigation showed no damage.
Thinking time and a re-enactment of the situation lead me down this path.
The situation:
exiting a dry sandy water course (not quite a flood plain, not quite a river bed) on a slight climbing left turn over a mixed surface. Tyre pressures were about 20ish PSI, speed was about 5-10 KPH 1/low with about half noise wound on and the approach was a slight but noticeable (perhaps 1:30) climb over the sand of the bed into the left hand turn and rising into a short (1-2m) crest up onto the strata (1:10 slope at best)
The kicking occurred when both rears were in sand, the front right was over a depression of soft sand and the front left was on a patch of frim, flatish rock with a grippy surface like pumice.
My initial thoughts were bump steering from hitting the rock but IMO the layout wasnt enough to cause it and when the problem demonstrated it wasnt one hit it was a series of small kicks of the wheel, similar to a seizing CV.
My current theory is that with the TT in the rear doing its job and pushing the vehicle forwards when the front left was climbing the rock it was slowing forwards motion enough that the rears were slipping or stopping in the sand and the unloaded front right wheel wheel was spinning. When the front right wheel spun it was enough to engage the TC and as it transferred torque to the front left the front left was trying to torque steer to the right.
to test the theory I put big red over the same spot but couldnt get TC to light up without giving it the berries, when TC did light up I didnt get the kicking in the steering just the usual Brrtrtrtrt of the ABS pump. In his vehicle I could replicate it but only by driving with his technique and taking a fairly precise line 3-4 inches either side or a couple of degrees different on approach would stop the kicking from occurring. Pulling the ABS master fuse also stopped the symptoms.
hope that helps.
