When it is low try pushing in on the lower right corner of the cluster. That will maybe tell you if it is the connector to the printed circuit

 

x2
.
or it could be real, probly not tho..
.
put a good quality mechanical gauge on it for a while, and see..
.
check the sender, see if its leaking any oil, if it is replace it??
or keep the mechanical gauge..
.
:texas:

 

Thanks I'll give that a try.

 

When I ush in on the right lower corner of the gauge cluster it makes the gauge go to where it was running. What is the correct way to tighten cluster so that doesn't happen? The screw is tight now.

 

464 may have some more tricks??
.
loosen the pod, and wiggle it in/out a lot, and tighten it back down, and hope its better..
.
some guys put foam tape under the printed circuit, to tighten up the connection..
and you can clean and re-arch [bend] the terminals on the connector..
but you have to take the whole pod out..
.
several tips and tricks in here
http://www.elcaminocentral.com/showthread.php?t=27161
like this
22) Cut a small block of wood to insert between the
plastic panel that holds the plug and the metal support structure. This panel
tends to deflect forward as you push the pod back on and after years it may get
to where it wont make good contact to the pod.
.
:texas:

 

Thanks JJ, good points to consider.