Kickdown to second gear for xj12 series III 1988

My GM 400 transmission will not kick down to second gear. Cannot shift down to second gear. Only first and third. Any ideas?

[quote=“abe7117, post:1, topic:354895, full:true”]
My GM 400 transmission will not kick down to second gear. [/quote]

Are talking about a full throttle kick down? Or perhaps talking about the part-throttle kick down that’s available only for 2nd gear?

If it’ll give a full throttle kick down to 1st gear then your kick down switch is OK. If it won’t give a full throttle kick down to 2nd gear only I’d suspect a valve body or accumulator problem, perhaps.

If full throttle kickdown work for both 1st and 2nd gear but you lack part-throttle kick down I’d first suspect a vacuum problem…as the part throttle kick down is vacuum controlled.

Externally I think the only considerations would be the kick down switch and vacuum modulator…or associated vacuum hose. Anything else would be an internal problem. But I’m not an expert; others will chime in.

Cheers
DD

Doug;
Thanks so much for your input. Full throttle at about 60 kph will not kick down to second gear – i.e. no passing gear. Will kick down to first gear at lower speeds. Also cannot manually shift into second gear at 60 kph. Partial throttle kick down does not seem to work for either. In my 1985 car I could select 2nd gear below say 80 kph and run up to 120 kph no problem. Normal acceleration starts in 1st but quickly goes into 3rd and stays there. The previous owner had several services to “free up kickdown cable” but I am not sure of the result. Any further advice?