I have a quest vanquish and the rear deraileur isnt shifting properly.

it will go to the largest cog when its only shifter into 4th

it shifts from 7 to 6 fine, 6 to 5 fine, skips right to 3 then, skips to 1.

Ive tried putting a new shifter on but it didnt change anything, i cant shift past 4th

the derlaileur isnt bent nor is the hanger.

any help PLEASE? =)

Did you try configuring it properly, or did you just put a new shifter on without first checking cable tension/H&L stops etc.?

Everything you need to perform an RD tune-up you can find here.

I might add that I commonly find "adjusted" shifting systems where the shifter hits low gear with the chain still in the middle of the cog stack.

Some serious cable-tensioning MIGHT fix it.

Also, note that the exact routing/placement of the inner wire (cable) at the anchor bolt (pinch bolt) can affect the ACTUATION RATIO of the derailer, and thus must be exactly as intended (in the groove) for the indexing to move accurately in response to the shift lever's movement.

Also check for smooth movement of the cable. Tug on the exposed length of cable running alongside the frame tube. The cable should move and recover it's tension as you let go of it. The action should be smooth and friction-free.

Always start with cable unattached, tension adjuster barrel screwed all the way in and then back out 1/2 to 1 turn at the most and the shifter in high gear. Turn the crank and make sure the chain is on the small cog. Now attach the cable and with finger tension on the cable, tighten the cable pinch bolt on the RD. Shift one click on the shifter, and then adjust the tension barrel out until the chain shifts to the 2nd smallest cog. Now test and shift through all the gears. And when the shifting works, shift back to the smallest cog (highest gear) and make adjustments to the stop screw if necessary. Repeat this stop screw adjustment after shifting to the lowest gear (biggest cog).

The above is good advice. If you are still having problems you can also Google adjust rear derailleur - Sheldonbrown and Parktool results are generally the best, but you can check videos for additional information. Go through the entire procedure and also make sure cables are running smoothly.

Please either take more time initially or use Edit Post to correct spelling, typos, capitalization, etc. We put much effort into crafting a clear answer, and it helps us in doing so if your question is clear and not difficult to read.

Thank you.