Jamar is a good unit but incredibably difficult to initially set up.
If you clean the heim joints located on the nose cone of the transaxle with "Brake Clean" then squirt the moving parts with spray "white lithium" grease, you'll see a noticeable improvement.
There are also a couple of heim joints inside the shifter box that need the same maintenance.
Anytime anyone comes to me for service or modifications, regardless of what kind of a shifter is installed, I clean and lubricate all moving parts and they all can feel a difference.
If you have a rod shifter be in Jamar or Beck, you need to do the same maintenance but you also need to lubricate the rod where it passes through the rear firewall and at the bushing under the engine.