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MSD controler lock up with 4l80 transmission

439 Views 0 Replies 1 Participant Last post by  chris3353
Hello all,

The 4l80 is in my tow vehicle,, not a race car. It has performed flawlessly with one exception. I installed a manual convertor lock-up switch on the dash. I use it when pulling a grade. I sometimes downshift to 3rd, lock up and ease up on the gas. All perfect so far.

MSD tech says it should lock up in second gear,, it will but only if the shifter is in drive or OD. If i manually pull the shifter to second the convertor will unlock, in drive it will lock.

I know second sound crazy but i live in Idaho, some mountain roads are steep and winding, 30-40 is all you want to go.

Anyhoo, My guess is something in the wiring but i have no idea where to start. MDS says it should lock up regardless of the shifter position. In first, the convertor will not lock as designed.

If anyone has a guess, it would be appreciated.