While working on making a front spring compressor was taking measurements and noticed one of the upper wishbone bushings was torn. The OEM rubber bushings are inexpensive and seem to be readily available from vendors. The Poly bushing are more expensive but don’t know if they are better or worse than the OEM bushing. Your Opinions Please.
Two things to keep in mind. First, the difference between OEM rubber and poly is usually not one of durability (unless the OEM has a design flaw, as in the case of the XJ steering rack mounts) but rather of stiffness. People go with poly because they don’t care for the mushiness of the OEM rubber.
Second, note that in many instances of things that twist, OEM rubber and poly actually work differently. This is the case in anti-sway bar inner mounts, for example: the OEM rubber bushings are designed to fit securely in the brackets and to grip onto the bar itself. When the bar twists, the rubber bushing simply flexes with it. When these bushings are replaced with poly, the bushing fits securely in the bracket but is intended to slip on the surface of the bar. This contact area therefore must be lubricated with a grease designed for use with poly (most hydrocarbons will attack poly) lest you get squeaks from this joint.
Now, I think the inner bushings on the upper A-arm in an XJ are intended to spin on the fulcrum shaft whether they are rubber or poly, so that might not make a difference here.