Here is the Garagistic rear subframe reinforcement kit for your E30, 318ti, Z3, Z3M rear subframe. It's not uncommon under heavy powered BMWs or track rat E30s to stress the four diff mounting points on the subframe which can break. That's where our BMW E30 rear subframe reinforcement kit come in. Designed for repair or reinforcement of the E30 rear subframe mounting ears about the diff (the attachment points).
As your E30 ages, the rear subframe can crack around the diff mount area. Especially under V8 swap power.