Joined: Aug 2005
Posts: 935
Likes: 46
From: Las Vegas, NV
Bikes: '04 LeMond Buenos Aires, '82 Bianchi Nuova Racing, De Rosa SLX, Bridgestone MB-1, Guerciotti TSX, Torpado Aelle, LeMond Tourmalet 853, Bridgestone Radac
There's no mention of what type of derailleur the new one is. SRAM makes Grip Shift for both Shimano and SRAM pull ratios. If the replacement derailleur was "the other", that's likely the problem
Even within SRAM you can get messed up...I run a commuter MTB with tight, road bike-style gearing and bought a Rival short cage derailleur a few years ago. It was then that I discovered that SRAM's 1:1 and Exact Actuation are not the same thing. I had a similar problem as the OP - it'd shift well adjusted for either end, but not both.