I have a 91 B350 and am not finding the info I need elsewhere so I thought id try here.
It has the A518, with overdrive and lock up. I don't believe its locking up.


I think I should hear if not feel the lock up in the 3rd gear range before it shifts into OD, but I only hear and feel 3 actions.


If its not going into lock up. where should I begin looking for the cause?


thanks for any help or advice in advance

 

Are you getting any codes? The PCM will set one for TCC if it doesn't see the RPM drop it expects when it engages. It only drops about 200 RPM as well....

 

when in the sequence should I be looking for lockup. I may be missing it, if its not very noticeable. im used to a GM lockup feeling like a separate gear change.

 

It varies....... or at least, so it seems to me.... Sometimes in third, sometimes in O/D.

 

Somewhere there was a post, but I cant find it now, where someone explained how to tell from the wiring under the vehicle if I have a lockup converter or not.
Can someone chime in? I know there is a neutral safety switch, but there is another harness near the rear of the housing. I think its a 3 wire, or 4 wire depending lock up or not,
Can someone confirm?

 

Near the rear of transmision there is a 3 wire plug. the center wire is your hot wire. When od engages it first grounds the wire closer to the rear. Then it grounds the wire closer to the fromy to lockup converter. od will not work if speedometer doesn't send signal. I hope this helps