OK, quick update if anyone has the same problem with autotransmission not changing into overdrive. It turned out to be the vacuum lines which go from the transmission body, back to the modulator and to the air intake. The modulator is a diaphragm which is responsible for gear changes. It has a ...

Hi All, I have/had the same problem with my 1991 Nissan Caravan, which uses the TD27 diesel engine - the same as in the Terrano I think. Transmission no. is 4N71B CA51. Had a look underneath and found two vacuum lines which had holes in. Sealed them and took it for a spina dn it started to change ...