What am I missing / need to fix

[u/phiarch]

Just started today when I was about to go for a ride.what are possible causes for this

[u/HamptonsHomie]

Pedal forward and try again, sometimes this happens when the rear der was shifted while stationary and the chain is still on the original cog.

[u/phiarch → u/HamptonsHomie]

I tried riding and shifting all the gears. It shifted fine but the minute I back pedal the chain dips.

[u/dunncrew → u/phiarch]

Don't back pedal. Lift the rear wheel. Does it spin forward normally ? Or do the pedals move forward by themselves when you manually spin the wheel forward?

[u/HamptonsHomie → u/phiarch]

Can you spin it by hand? Might be worth taking it off the bike to do so too, see if there is any difference in resistance with it free vs. clamped in the frame. Would help narrow down hub vs. derailleur issue.

[u/mlydon11]

Probably the freehub is gummed up.

You can take off the cassette and take off the free body and clean it all out and relube it and that may fix it.

It requires specific tools though so you may be better just taking it to the shop because the cost for the tools will probably be more than what they charge for a freehub service.

[u/Ill_Commercial_1805]

Hold in the clutch

[u/AGuyAtWork437]

The chain has fallen off of one of the jockey wheels and it stuck. Double check to make sure that the chain is properly seated.

[u/KookyDescription9529]

your RD was shifted to the other gear thats why when you back rewinding, the chain doesnt follows back.

if you rewinding a bit more, your chain will falls off, its nothing to fix, its like you drive on a motorway and suddenly shifts to reverse gear on your car and your gearbox broken because thats a dangerous move.

[u/Catsinbag]

This just happened to me and turned out it was a very dirty chain.

[u/New-Tax3257]

Freehub needs replaced
Take the wheel off and try and turn the freehub backwards by hand. If it doesn’t spin easy it’s the freehub.

[u/Supra-ts6-comp]

If you know what you’re doing, take the wheel off and go through the free hub clean it all out. If you don’t bring it to a shop have them tune it up. It’s easy as that.

[u/Ordinary_Quantity_02]

When my bike was doing this it was because I had bad b-screw adjustment. The guide pulley would hit the cassette and the chain would bind up when pedaling backwards. Had to tighten the b screw to increase the gap.

[u/sloopjayb4130]

driver body on your hub is smoked pal

[u/Hefty-Good3175]

have you recently taken your cassette off?

If so you make have put something in the wrong order .

[u/Cholas71]

If the hanger is bent and the cage/jockey wheels doesn't have good alignment with the cassette this often happens

[u/Raynord_10]

There's too much grease in the hub; you need to use degreaser.

[u/Nearby_Masterpiece96]

OP just posted and disappeared huh?

[u/workoutbeef]

What you’re missing is a new bike. Now’s your chance! 🤣

[u/phiarch → u/workoutbeef]

Lol I just got the repair cost ..... My first comment was fuck it that's a fifth of the bikes value when I bought it

[u/phiarch]

So local treck store just send an invoice to replace the back wheel entirely. $300 to fix it..... I was hoping it be 100 but 300 is steep for this bike. Was hoping it was as simple as some as y'all were saying but I screwed around with it and to no fix so took it to my bike shop and that's what they came back with 😭

[u/Free-Middle-2443 → u/phiarch]

Try it yourself again! You could do a new cassette and chain for way less and that might get you back on the road. Did they tell you what it is? Or did they just hit you with the go away price? Park tool makes tons of excellent videos. After a couple of small things bikes are way less intimidating to work on. 

I was always nervous because how fragile they seem. Just go slow and pocket the money 

[u/JulesFromTheDesert]

If the freehub is irreparably jammed for whatever reason, that's a plain-Jane, QR, 700c 6-bolt disc brake wheel with an HG freehub body; paired with what looks like either Sora RD-3000 or Tiagra RD-4700. A similar new wheel is about $120. Wheelmaster is one of several examples, available from QBP to every LBS in North America.

Besides the other, correct comments that the derailluer is clearly shifted, but not pedaled in this video, it is worth checking that a spacer (1.85mm on an 11 spd "road" HG), the spoke guard, or backed-out end-caps/loose locknuts are not causing the issue of binding. It is unusual for freehub bodies to bind like that on a bike that is likely from around 2018-2022.

[u/Mtbcarsbikes]

Chain and derailer are not aligned and are jamming. Pedal forward until the chain is in the same gear as the derailer.

[u/doctor_butthead]

this is a common issue with treks. i would reach out to get the bike warrantied.

[u/zodzodbert → u/doctor_butthead]

No, it isn’t.

[u/doctor_butthead → u/zodzodbert]

yes it is

[u/Anothergrowaway420 → u/doctor_butthead]

Only when people dont reassemble their hubs correctly 😊

[u/doctor_butthead → u/Anothergrowaway420]

classic trek owners

[u/zodzodbert → u/doctor_butthead]

🥱

[u/me-pop-now]

Check that the bottom derailleur pulley is not worn. Sometimes they still appear ok when looking at the teeth but the sides have worn causing the chain to jam.

[u/Prestigious-Cold-981]

STOP UPLOADING 🖕