Just had the same problem. 3rd gear gets to about 4500, throws into neutral than back into third. was on the way back to mechanics to adjust ( just had zf tune , .7 front cover and 100lb injectors installed. 390rwkw) and a rod bolt let go. punched a hole through the sump. wouldnt be suprised if the trans playing up contributed to this. dont know whats next yet :-(