I have a 2004 Trek Navigator I'm trying to fix up. Everything seemed fine until I switched gears and heard loud odd noise plus my pedaling got alot harder. Upon inspection I found my rear derailleur almost completely opposite from where it's supposed to be. Hard to explain. Instead of being down from cogs, it is in the back and slightly above cogs! Thus causing the chain to rub and grind on derailleur. How did this happen? How do I fix it? 
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5Did you change the chain? It looks like it's too long.– Weiwen NgCommented Sep 22, 2022 at 14:28
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Please change gear to big-big and then take the same photo again.– Criggie ♦Commented Sep 23, 2022 at 20:01
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No I didn't change chain– AlisonCommented Sep 25, 2022 at 6:27
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I cannot upload another photo it says it's too big over 2 mib– AlisonCommented Sep 26, 2022 at 18:18
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@Alison Search up "photo compressor" online and compress the photo a little, then try again!– MaplePandaCommented Sep 29, 2022 at 21:48
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1 Answer
The chain currently appears to be too long. It's close to impossible to diagnose from your photo, but would you check your upper pulley wheel is OK. If it has disintegrated and fallen off, it would cause some grinding. The derailleur is very old so it's not impossible. If you update your question with some better/detailed photos, I will update my answer.
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Concur - the chain is set on the smallest chainring and the smallest cog so all the spare chain has to go somewhere. Perhaps OP can shift to a larger chainring and improve things.– Criggie ♦Commented Sep 23, 2022 at 20:00
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1We can see 1 tooth of the upper pulley so it hasn't fallen off at least. Looks like either chain too long or bike specced with derailleur without enough capacity. Very likely things will work ok when using an appropriate gear combination– Andy PCommented Sep 24, 2022 at 13:12
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@AndyP i don't know how you can say that definitively from such a crap photo.– NoiseCommented Sep 24, 2022 at 14:46
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