VN drops back a gear when speedo drops out

[V8commodore_chick]

I've got one of those dodgey dash clusters where the speedo drops out now n then and sometimes works again when thumped (I've given up thumpin it only hurts me hand anyway lol)
Anyway when the speedo drops out the car drops back a gear and revs a little higher. Why is it doing this?

[greenfoam]

Good imagination? lol
No actually you might be losing power due to a shonky connection to the part of the cluster that divides the speed sensor pulses by five and then sends it to the ecu which then means the Torque converter lock will unlock, giving you more revs and an easier kickdown into 3rd. That's the best theory I have for you

[V8commodore_chick]

The whole car is shonky lol
I'm looking at putting a new cluster in anyway but one with a tacho as this one dont have one.

[xcop5l]

if the speedo sensor is faulty it will send a signal to the computer saying your goin no where and it will unlock the converter.then when you get a reading it will lock it back up again
it wont drop the transmition back a gear as thats still mechanically controlled
so first test change the speedo sensor

[V8commodore_chick]

Thanks for that xcop5l that actually makes sense.
This might sound like a silly question, but I'm female so I'm allowed to ask them hehehe Where is the speedo sensor located?
I've looked everywhere in the manual but cant find it anywhere

[xcop5l]

if you crawl under the car you will see the transmition(big silver thing) its in the extension housing on the drivers side (from memory) and it has wires coming out of it.
the extension housing is the bit at the back of the auto that is smaller than the auto and it conects to the tail shaft

dont worry there are no stupid questions, only stupid people for not asking them

[V8commodore_chick]

Thanks xcop51 I think I may have found and fixed the problem, it was actually on the left hand side and there was a loose bolt holding it so I tightened it and hopefully I fixed it.
Thanks again xcop51

[MyVPIsFasterThanYourVP]

I was driving on the freeway tonight when my speedo dropped to 0 from 100kph, there was a brief cut in power from the motor, then even though the speedo kept jumping around, and even stayed at 0 for a bit, all seemed fine powerwise till I got home, I guess at daylight Ill be climbing under the car to check out my speedo sensor, hope this thread is my cure, willl post back when I know.
Colin

woo hoo, it was a loose speedo sensor. Just screwed it in tight, and all fixed!