I Have a 97 F-150 4X4 ORP with manual trans and had a problem with my spider gears. I noticed while turning that I had a clunking noise (if not lack of a better word) in the reared. I needed to replace the right rear axle seal because it was leaking into my drum. I took off the differential cover to discover that I was missing a tooth off of one of the spider gears. With no money I had no choice but to only replace the seal and wait on the gear. With this I was just waiting for the entire rearend to shatter and have to get an entire new differential. I have a limited slip reared and both of the spider gears had a tooth tore off. I was wondering that since Ford F-150's have a problem with the manual trans clunking into gear, does that have a play in the gear becoming damaged? I was told by a mechanic at the dealer that Ford F-150 with manuals tend to clunk because the trans and differentials are set for autos and the driveshaft has to move forward to engage in because of the shortness of the manual. Is it possible that this clunking is how the spider gears became damaged? Now this clunking was enough to make the rear tires bark while still in first. When I started hearing the clunk I went directly to the dealer and asked what the noise was. The dealer was extremely helpful and drove the vehicle and told me what the noise was, and told me how to fix it with no charge. They even told me they would give me the grease for free (The grease went in the front of the drive shaft, to make it slide easier into the trans). This occurred at around 86,000 miles Now I have 94,000. Do you think this might be what made the spider gears go?