96 XJ Speedo jumping
 

While driving on the highway today my 1996 Jeep Cherokee Sport 4.0 litre
my speedo needle started jumping back and forth then as I slowed down it stuck around the 40km mark until I started to speed up again.
Whats causing this and how do I fix it.
Thanks

I would assume at this vintage the XJ is using a electronic speedo not a mechanical one. On that assumption it is likely the actual instrument movement is faulty, likely wear in the spindle bearing inside the speedometer movement. I wouldn't imagine it would be hard to find or terribly expensive the find a good secondhand speedometer cluster for a XJ, the lower the milage the better for low wear.

both mine do this, check the archives, the fix is apparently to remove speedo and fix loose wire/ poor connection

short-term fix, rap the speedo face, seems to work

maybe some sort of light lube around the needle/bearing area, if possible, it seems more like "sticking" to me

or get a "heads up" GPS.... projects speedo on windscreen.. about $50

When its stuck on 40, if you tap the instrument face, does it drop to zero?

Well a fist slam on top of the dash has stopped in from misbehaving and it's working alright for the moment for how long I will just have to wait and see.
I already have a gps so I can use that if needed.
Thanks for your replies.

yes, it does... well sort of, it will either stick on 0 or 40, and usually spring to life, if not, rapping it will either jump to ok, or 0, then jump up to ok

are you aware of a known fix pls ?

only started recently on the black DD, the white one has the same symptom

You will see on the comments there are 2 suggestions,
1/ a bad electrical connection some place
2/ the needle is sticking.

From what you have just said, it sounds like a sticking needle.
A pain to pull the instrument out & to bits, but it probably has dust in the bush & the lube has dried out.
A quick fix is to very carefully put some (less than a drop) of oil on the bushes, ATF is good or you could use a very thin molli containing oil. Graphite powder may also work but it can be messy.
Work the needle back & forth around where it was sticking until it frees up.
Good Luck ! its like being a watch repairer.