Speedometer problem

I'm finding lots of discussion about recalibrating a speedometer, but nothing yet regarding my issue.

I have a 2005 Tundra DC. The speedometer works accurately most of the time for short trips, but I can't trust it if I travel more than about 20 miles and have to use my GPS for backup. Sometimes I'll be going 70 and the speedo reads 70. Then I'll look down a few minutes later and it reads 85 or more while still going 70. If I come to a complete stop, it will still read 15 mph or whatever the difference was. If I shut off the truck and open the door, then start it again, it will reset to zero. Then it will be fine for a while and might decide to now read 60 when going 70. Most often it goes high, but sometimes low.

Dealer told me I needed to replace the speedo head for 2k+. I'm not buying that answer. Does anyone else have an opinion?

Thanks

 

Thanks ColoradoTJ - not sure I want to hand over that much cash, but good advice.

 

Actually my father-in-law trades in his Platinum Tundra every 2 years and he's due again as soon as the '18 models come out. On his last round, it was all arranged for me to give my truck as trade-in and buy his direct, but it would take $30k (I won't finance anything but a house). Just didn't feel like forking over $30k at the time, but I wish I would've. Might have to do it this year.

 

Any news on what fixed the problem? I am in the same exact situation.