This is a common problem with the GM 5L40-E transmission used in the 3.0 litre models (generally caused by the reverse lockout valve sticking) but it’s unusual in the later ZF 5HP24s used with the M62 engine.

Early 5HP24s had problems with the F-brake piston seals which would wear and leak preventing pressure building up behind the piston and hence reverse was lost (the C-clutch & F-brake being engaged for reverse) but this was sorted in the late 90s.



The only 5HP24 that I’ve rebuilt specifically for losing reverse was caused by the O-rings failing on the C-clutch support bush (the sleeve having rotated in its housing). However there was still some pressure build-up and the vehicle would just about move backwards if gently nursed.




The fact that your failure happened so quickly though is curious. The 5HP24, like the 5L40-E and any other modern transmission for that matter, has a reverse lockout which prevents reverse being engaged at forward speeds above 5mph if the shift lever is moved (accidentally) into reverse while the vehicle’s travelling at speed. The 5HP24 has a shift solenoid (solenoid #3) in the valve block specifically to perform this task but it seems unlikely that it would just suddenly develop a fault in the situation you described. I guess it’s possible that the lockout valve has become stuck?

It makes no difference whether the transmission fluid is hot or cold?

Phil