Maintenance Standards for Locally Driven Straight Truck - Broken Instrument Panel

I recently took a job that keeps me home every night driving a straight truck doing local deliveries. The job is 100% intrastate. I really like the job (and sleeping in my own bed every night!) but the vehicle maintenance standards at this place are, shall we say, not quite what I got used to in my previous OTR jobs.

I recently ran into a situation that I'm not sure how to handle.

Basically, there are problems with the truck's instrument panel. The fuel gauge doesn't work at all (not a big deal since I rarely use half a tank in a day and refuel at the end of each shift). More seriously, the speedometer has been having problems. It routinely "sticks", so when I'm accelerating, it tends to show a lower speed than I'm actually traveling, and when I'm braking it tends to show I'm moving faster than I really am. It's routinely off by as much as 30-40 mph. Because a lot of my driving is at night and in light traffic (when I can't really judge my speed relative to other vehicles), I'm worried about ending up with a speeding ticket.

I've reported it a few times on my DVIRs and directly to supervisors, but so far nothing's been done.

My question is, is this problem enough to put the truck out of service? How should I handle this? How hard should I push? I know this particular problem isn't officially listed on the FMCSA regs, but it strikes me as being in a bit of a gray area where safety is concerned.

Thanks in advance!