I've seen two different types of slip clutches on JD implements. The kind I have on my JD tiller is identical to the kind supplied on the Landpride RTA25 and RTA35 tillers. Deere doesn't describe any check/adjustment procedure for this slip clutch in their manual (!), but Landpride does (thanks, Landpride) and you can download the tiller manual with excellent drawings (so you can tell if that's the kind of slip clutch you have) from Landpride's website. The other style of slip clutch I've seen on JD is similar/identical to the type found on the Landpride RCR2660 and RCR2672 Rotary Cutter. I assume this will be similar to what you have. Again, Landpride has excellent diagrams and adjustment instructions in the manual for these cutters. Unfortunately, the adjustment "technically" involves knowing the original compressed length of the slip clutch springs. I'm sure you can fake it after you free up your clutch by equally compressing the springs in small increments until the clutch again stops slipping under normal usage. Or maybe someone (dealer?) with a manual for your cutter can tell you the original compressed spring length so you can begin from there and save yourself alot of adjustment time. Best of luck.
Bernie