Hybrid Bicycles - Gripshift/Derailer prob?

I've a prob. Not sure what to do to fix it.
It's a new bike. Giant Escape R3 (http://www.giant.co.jp/giant09/bike_datail.php?p_id=L0616102&action=fullspecs). [[some Japanese]]

F. Derailer - SHIMANO T301 31.8
R. Derailer - SRAM 3.0
Shifter - SRAM 3.0 TWISTER 8S
Gear - SHIMANO HG40 8S 11-323T

-On any of the 3 front cogs -
If I pull the (right) Gripshift knob/changer slightly beyond 1 (lets say, towards imaginary 0), the chain shifts into gear 1, but the moment I let go, it wanders back into gear 2.
When I slide the gripshift into 6, the chain shifts to gear 8.. so 7/8 on the gripshift don't do anything.

Gear 1 --> 2
Gear 2 --> 3
Gear 3 --> 4
Gear 4 --> 5
Gear 5 has become 6/7/8 (no movement when shifting into 7, or 8)

I noticed there's slack on the cable when the gripshift is on gear 8, and the gripshift knob moves loosely.
Does it wind down to the B-screw/H-screw/L-screw adjustments?

Any ideas/suggestions are much appreciated.

sounds like it needs a complete tune up. h/l screws should be adjusted so that the top idler wheel is centered on the outermost cassette cogs. The B screw is just to keep said idler from contacting the cassette teeth with chain on. Once h/l screws are properly adjusted, if the cable was installed properly, all that remains is fine tuning, via adjuster barrel, of the rear derailleur. One reason I wont own SRAM is the lack of adjuster on rear derailleur, its more convenient there when tuning.

http://www.parktool.com/repair/readhowto.asp?id=64 a much more thorough explanation!

My girlfriend has about the same exact set up on her Trek 7100, and It has never needed tuning whatsoever. I put a new chain on this year and gave the l/h screws a very slight adjustment, but shifting was still crisp as can be.

thanks for the tip nymtber. i'll print out the instructions and take'em with me tomorrow and see if i can fix it up. if i run into any bumps (most prolly will), i'll be sure to post an update. :thumb:

So I poked around a bit, turning screws quarter rotation at a time and pedalling with my hand until finding a medium where the difference between the gear changer and the actual gears was not as big, but it kept pestering me so I took the bike to the shop where I bought it and had them take a look at it. In fixing the clinking clanking, they pointed out the chain was hitting the plastic disc (between the cogs and the tire) and said there was no problem in removing it, so they did.

But today, something just didn't feel right. I think the cable is a little slack in the grip shifter.
When I'm in a certain gear, I need to hold the grip shift half a notch back, so that the derailer lines up and the chain doesn't hop from (for example) 4 to 5.

Just sounds like there's not enough tension in the chain. Try tightening the barrel adjusters. These are the little barrels that the cable housing goes into at either the derailer or the shifter. Try turning them so that the slack in the cable is taken up.

FYI: Sheldon Brown has a good article on this:
http://www.sheldonbrown.com/derailer-adjustment.html

There is absolutely no reason to remove the dork disc to avoid any other part coming in contact with it!

They need to do a thorough adjustment of that rear derailleur, which may include straightening the mounting tab.

Poor mechanical skill on the part of the shop, IMHO!

Make them make it right, or find a more competent shop........

There is absolutely no reason to remove the dork disc to avoid any other part coming in contact with it!

They need to do a thorough adjustment of that rear derailleur, which may include straightening the mounting tab.

Poor mechanical skill on the part of the shop, IMHO!

Make them make it right, or find a more competent shop........

+1 on this. I've never removed those dorky plastic disks and never had shifting problems.

You could have more than one item here.

Potential issues from my perspective (no particular order):

Bent derailleur or hanger
Improper adjustment of H and L
Improper tension of cable (adjusted with the cable keeper bolt or barrel adjuster)
Cable is not operating smoothly (i.e. bent casing, needs lubing/cleaning etc)

Just got back from a mostly smooth ride, and boy was it nice.
Did what you guys suggested. I started with the Barrel Adjuster.

Did a further search for Barrel Adjusting on this forum and found this little treat
http://www.bikeforums.net/showpost.php?p=3139330&postcount=7

Thanks again for all the suggestions. :thumb: