r0ckh0und 

Been riding a steel hardtail since the turn of the century and picked up a GF HiFi Pro this spring, used, possibly abused. I have ridden a couple of suspension bikes on trips and borrowed one here and there. I sometimes notice some creaking noises on these bikes and particularly the one I am riding now. I lubed the pedals, pulled the cranks and cleaned them and applied a light coat of grease to the shaft and splined ends, but I am still getting a small creak/click everytime I'm on the downstroke on the drive side. Is this the frame linkage creaking? Is this normal? Is there a maintenance procedure I can do to eliminate this, or at least attempt?

scrublover

Check your seat/post/seatclamp.

Then start looking at your suspension pivots/bolts/shock stuff.

Likely just needs a clean and re-grease of things. Make sure things are not too loose/not too tight. Without knowing the particulars of your frame, or its specific torque specs, it's hard to say more. Take the rear shock off and cycle the suspension. If things feel tight or notchy, you may have blown bearings or pivots. Start taking things apart. Clean. Grease a bit. Put back in the same way you took 'em out. Tighten up enough to get rid of lateral play, bolt the shock back up and see how it goes. May need some Loctite or something on some of the bolts to keep things from backing out. NOT on the bearings or pivots or bushings.

You may also just need new DU bushings on the rear shock.

Tough to tell more without actually having the frame to see.

Dannihilator

What year is the HiFi? For awhile that model was prone to failing.

clydeosaur

I find that when I wash them good, they sometime develop squeeks/creeks due to dry pivot points in the suspension. Relube until sound goes away & you will find your culprit unless you have some other problem. Check bolts & bushings as well for rust, corrosion & proper torque.

ed 

The last creeky noise I had to fix was my cassette. I removed the retainer, cleaned/lightly greased the outside of the freehub body where it contacts the cassette, re-assembled. Sounds great.

GDA

Check the torque of the crank to the chainrings and also the pedals to cranks. If those check out then move to seatpost and stem/headset as you weightshift might be causing the issue per pedal revolution.

Also, since the bike has been ridden some, I'd go ahead and retorque all the suspension pivots in the back end. I've found this really brings back that sharp taut ride to a full suspension bike.