OEM antenna/cable required or ok to use my smaller retractable usb cable for traffic

Just try it, most USB 2.0 isn't too fussy with basic cables. Just don't force any connectors.

if its like my 3790T it needs the larger "power" cord as this supplies not only the power but also has the traffic aerial and receiver in it.

The receiver box also has a connection for an extra aerial lead but I have found that this does not not much difference.

Thanks guys.

I tried plugging my cell phone charging cable into the GPS. It didn't break anything and it may even work for charging the GPS's battery, but it's not the solution I need. When I plugged in the cable, the GPS first showed the screen it does when I connect it to my computer, but then after several seconds it changed to normal gps mode. However, it did not show any traffic info, so it seems the big bulky cable/antenna is necessary.

Too bad Garmin doesn't sell a product of some kind that would help people like me who are willing to spend a few (few!) more bucks on a solution.

I have the same problem with my Nuvi 2555 LMT

The antenna is built in and used to work, but now it says traffic cable is needed - I bought a traffic cable and now get that same computer screen till goes to normal GPS mode, but STILL NO TRAFFIC! 

Garmin helpfully tells me "Lifetime" traffic is for the lifetime of the GPS, and since it is not receiving traffic, it's "lifetime" is over. 

I have the same problem with my Nuvi 2555 LMT

The antenna is built in and used to work, but now it says traffic cable is needed - I bought a traffic cable and now get that computer screen till goes to normal GPS mode, but STILL NO TRAFFIC! 

Garmin helpfully tells me "Lifetime" traffic is for the lifetime of the GPS, and since it is no not receiving traffic, it's "lifetime" is over.