Speedo drops going over ribs in the road

Hi all.

I live in an area where they use lots of raised yellow lines / ribs across the lane to warn you of a concealed junction etc or just to slow down. There are also loads of cattle grids.

If I go over either a cattle grid or these ribs but Speedo drops drastically. It reads 15 under anyway which I need to fix, but whilst travelling over the ribs it drops at least another 10-15 mph and won’t recover unless I switch the car off and in again, so not the most practical solution.

Anyone had this issue or know a way to fix it?

Many thanks in advance.

I'm guessing you have an electronic speedo ?
Which to be honest I know nothing about.
Mine have all had cables, driven by a small cog in the back of the transfer case behind the handbrake drum.

Hopefully you'll tell us what car you have and the appropriate person/group will be able to assist.

miktdish said:

I'm guessing you have an electronic speedo ?
Which to be honest I know nothing about.
Mine have all had cables, driven by a small cog in the back of the transfer case behind the handbrake drum.

Hopefully you'll tell us what car you have and the appropriate person/group will be able to assist.

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Sorry I thought it would put my vehicle blower after I set up a signature sort of thing but I’ve clearly done it wrong.

It’s a 1998 defender 90 TD5. I have not a clue which type of speedo it is becuase the previous owner has just whacked anything into it so i have to figure it all out the hard way.