I just got a 95 SWB with 150k on it, it was shifting rough so I had my land rover mechanic drain and fill the transmission fluid as well as change the filter, it was very dirty and had sludge in the sump. It certainly seems like no one changed it in a long time. Well after he did that i drove it for 5 miles and it drove perfect and shifted extremely smooth like it was designed to, but right after that it started acted like it was in neutral, the engine would just rev and it would not move forward I couldn't put it into R or D. If i turn the car off and back on it would drive fine for a few city blocks then the same thing again and it would act like it was in N again. Would the new filter be clogged by any chance? Would a full flush fix this or is the transmission gone?