runs good if ya acc past it but at 50 mph when it goes into overdrive it goes in..out..in...out til you accelerate bout 5 mph or decel 5mph. trans is strong race unit from a local builder. been ggod for 6 mos now doin this

any help where to start.
checked fluid level...good
checked kickdown cable...good
all elec connections seem okay...

billet triple disc converter....not slipping

 

Could be anything from poor ground on batt cables to TPS switch funked up to wire on alternator needing shielding.

Im going through the same thing right now, eliminate 1 possibility at a time. Many threads here to search through, common problem and lots of info here to fix it.

 

i had a problem like that and all i had to do was grease the kickdown cable and adjust it some, idk why it was doing it

 

I had the same problem. Disconnect the batteries for 10 minutes or so, then reconnect and drive. If the problem is gone (it will come back soon) then you have either too much electrical noise from the alternator, or a poor ground, or both. On mine, it was the ground for the alternator. The ground wire has a connector on it, located under/near the passenger side battery. I removed the connector and spliced the wire, and haven't had a problem since then, over a year now.

 

Mine does the same thing and I know it the TPS. What I do to make the problem go away for awhile is, with the truck not running I press the go pedal up and down about 10-15 time and it cures it for a month or two.