SC400 jumps on reverse with dash on and off
 

Hi, friends.
Recently my SC4 1994 developed very weird problem.
Steps to reproduce (when it happens)
Setting the car in reverse
Turn the wheel left and right
Dash goes off for a second then on
When dash goes off, the car gets out of gear
When dash turns back - car gets back into gear.
by getting off and in gear, the car jumps like crazy

If i reverse straight way - everything is good.
veeery weird!
p.s. my speedo sensor on gearbox is dead
Trying to figure out, any help highly appreciated

Bro, Please rewrite everything more clearly. I can hardly understand what your trying to say and when diagnosing a problem you need to be crystal clear.

Is it physically jumping in and out of gear, or is it just the indicator on the dash ?

rewrote with steps to reproduce :)

physically. The dash is completely off, when it happens you can press on throttle and the car will not move, like in Neutral.

Not sure if possible, but is the car lowered a lot and you didn't relocate the wiring harness in the driver side fender-well? I ask this because turning the wheel seems to have an effect.

check this i had this issue causing lots of strange problems. id check it lowered or not.

Does it seem like the engine dies or just pops out of reverse and into neutral when your reversing while turning the wheel

the car is lowered, but far from touching anything. Fender to wheel clearance about 0.7-1inch. Nothing is scratched above the wheel, just checked.
yes, the is not shuts off, just turns the dash off and jump into neutral, when dash back on, car gets into gear again.
basically, what you say is that it is clearly electrical problem ?
i have a lot of electrical problems that i am solving slowly, this car became headache :(
previously i had ignition problem due to bad connection of gearbox oil temp gauge, someone connected it to one of wires coming from ecu, the vehicle was burning like 25 liters per 100km on hwy, located and fixed it... Now i am still having other electrical problems... Probably have to re do all the wiring from scratch
thx