My 5th (highest) gear on my 10 speed is slipping every quarter to eighth of a turn, more frequently with increased load. Gears 1-4 work just fine, even under high load. The gears do not look worn and the chain is in good shape, everything is clean and lubricated. I can't seem to figure out why this is happening. Help!
Could be either a worn chain (even if it looks ok) but I'm going to guess worn freewheel (ratchet inside could be worn out). If you replace the freewheel, I'd get a new chain anyway. Note that you might be able to fit a 6 speed freewheel depending on the width of your frame.
Take a closer look at that cog on your cassette. I had the exact same problem, all the teeth looked healthy it was a fairly new cassette. Somehow I had broken one of the teeth off and it was causing my problem. I never noticed it until I had the cassette completely taken apart. I had missed it up until that point. I had almost bought a new crank set and chain because I though it had to be the problem.
3 main possibilities as I can see. As this occurs in top gear only it is probably not the freewheel pawls or you would have problems in all gears.
1/ stiff link in chain, turn the pedals backwards and look for jumping as chain goes over the teeth and through the RD, a stiff link should show as a vee in the chain and can be freed using a chain tool.
2/Rd mis-aligned or slightly bent, look from the back and below at the chain on the teeth, if it touches the next ring up it will try to climb and then drop back, adjust the stops as required and fine tune using the barrel adjuster.
3/ worn teeth on the top gear ring only, look for hooked or damaged teeth, note this ring wears quicker than the others as it is generally the most used and has less teeth to transmit the power.
Chain line may be a factor but is not usually a problem on 5 gears set ups.
![[-]](https://forums.bikeride.com/images/flatty/collapse.png "[-]")
