any explanation for Max Speed 153 mh?

The speed thing, even though possible with the right car or bike, is a possible glitch. I have seen other people report about outrageous speeds displaying on their GPS for no apparent reason. A sudden power surge or similar can trigger such a glitch. Driving over a pothole could have possibly jarred the unit where it momentarily lost the connection, who knows. IF it works otherwise, I wouldn't worry about it. If it happens frequently, I would report it to Garmin.

the unit achieved an initial minimal satellite lock followed by a (very quick) correction once it got additional satellite signals? That's the only thing I can think of other than the tooth fairy borrowing your car in the middle of the night.

I'd think it would have to be a miscalculated position or dropped signal, followed by a good one.

Maybe it's still in your track logs. Load the tracks into Mapsource and then double-click them and look at the 'legs'. That might show you roughly where your local version of the "Bermuda Triangle" is.

Momentary loss of signal would also be my guess for 153 mph max speed. I've seen something similar on my Nuvi 265wt also...and my Pathfinder is DEFINITELY not capable of such high speeds!!!!

Also on a recent trip, my unit would not turn on when I went to program our next leg of the trip and I know it was fully charged. I thought i would have to return it to Garmin (only 2 months old) when I got home. However, when we got back in car, I went on ahead and hooked it to to DC adapter. Within a few seconds it came back.

Other than that glitch, we've enjoyed our unit.

I had a Garmin Vista that I used on hikes and it would show instantaneous rapid speed increases after loosing satellite contact for a short period. Surely that's what you're seeing. It's not really a glitch, just that they must use an algorithm that doesn't allow coasting when contact is lost.

My nuvi 360 shows 547mph max speed

I turned it on a flight and did get a signal after a while

I had the same thing happen. Mine showed a max speed of 112MPH one time, which I thought was accurrate since I was being stupid one day and driving way too fast. Unfortunately, when I dumped the tracking logs, I found that the 112 was caused by a missed reading immediately before it. My speed in that section was averaging 55-60 and with one missed mark, the next one corrected and doubled the speed making the momentary 112MPH reading.

Now the three or four marks at 108-109 about a mile previous to the error... [innocent gaze]

Jeff

I believe mine has a max speed of 254 shown. Not likely in a 4 cyl Ford Ranger pick up. At the time this happen my track was not on the road but out in the woods somewhere. The device was having a problem getting and maintaining a signal. Since then I have used it in much worse weather and through the same area with no problems of maintaining a signal. Sunspots or something else I guess. This is with 265T. Now downloading the 2010.20 updates for but that is for the other thread.

I have both a Nuvi 750 & 760. The first time I saw 127 MPH on my son's GPS I blew a gasket. When I was assured that he had never driven that fast I was less than impressed... It was only during a 700 mile trip on my 760 that I experienced a max speed of 133MPH... Since I was the only one driving I know that it was BS... I now take the max speed with a grain of salt....

jb in atl

Garmin!!!! Gremlin!!!!
Add water, now use your imagination.
By the way, was there a full moon out that night?

See now, there's your answer.
Another mystery solved.