This is the first post that shows up when searching for this issue so I thought I'd share my fix here.
I recently picked up a WD-73638 for $100 that had the color wheel issue.
While some use the Sharp GS2P40 photo sensor, mine used the GP2S70 which is the replacement for the former. The difference between the 2 is the new one is a surface mount part vs the thru hole design of the older one and is not easily replaced. Digikey etc have the 70, you have to get the 40 from China via eBay.
However my TV would work fine for about 1 minute before the colors would shift and flicker. I did purchase a used color wheel off ebay, however that one would work for about 30mins before it would go bad as well, luckily the seller refunded me so I wasn't out any money there.
Since I now had a spare color wheel and knew it was a heat issue I decided to play around with the issue While I tried to find someone who could replace the SMT Photo Sensor.
So I took the sensor board off the color wheel and used some Arctic Silver 3 thermal compound that I use on heatsinks and some Super Glue and experimented. I put the super glue around the outside edges of the sensor to insulate the exposed contacts since the thermal compound is conductive.
After that dried I put a decent sized ball of thermal compound on the side of the sensor closest to the large indexing hole, I then trailed the compound over to the holes. I then reattached the sensor to the color wheel. I also put it on the feet of the color wheel where it attached to the light engine.
I did all of this with the color wheel that would only work for a minute and I'm happy to say that it's been running strong all weekend.. So far it's been on and problem free for the past 10 hours today alone.
Be careful not to get any on the top of the sensor tho or you'll just end up blocking the leds and ruining it.