4+3 overdrive problems

Ok, I've been chasing this gremilin for a cpl years now, every now and then my OD would drop out while I was on the highway, well it seemed my alternator was going bad and producing too much voltage intermittently, this would turn my OD off along with some other things in the car as well. I replaced the altenator and took the car for a ride...got to temp...turned the OD on and wa-la..it worked...for about 10 miles...then started kicking in and out...few mins on..then off for a few mins then back on..over and over...checked all the connections..the relays(changed when altenator went bad) and the switch.....so heres what I'd like to try next...I want to direct wire or bypass the ECM to have the OD come on whenever I flip the switch...I have seen in the past others who have posted about doing so but now can't seem to find much info on it..can anybody help? Heres what I have found.....intercept the brown/tan on the OD relay and run that through the switch to ground.....is this correct? Thanks guys

What switch did you replace? The manual switch or the switches on the tranny side cover?

Could be an ECM control ise, if all else fails you could rewire it to bypass the ECM and only make it work w/ the manual switch.

Ddi you check the filter, fluid level and so on?

I think if you press the OD switch before driving off, it switches of the OD. See what it does then when you manually engage it.

A 6 speed conversion will cure all your problems .....