I have been working on my 94 F350 E4OD and have fixed all issues dealing with trans and torque convertor. Truck is shifting good and new torque convertor is solid.

After getting everything working I was out driving the truck and noticed the speedo surging at speeds around 55-60. I checked speed sensor and repaced it with a know good one and still the same thing happened. Then while on the test drive I took it out of overdrive and speedo settled right out cruise worked as it should. Put it back into overdrive surging comes back cruise surges with it. Tack is working perfectly steedy. I am seaching thru my trouble shooting but havent ran into anything like this before havent decided what to check next.

 

When it surges, does the tack change rpms even slightly?

 

No the tach holds nice and steady, watched this very carefully and checked several times.

So far my next step in my mind is to clean and check all grounds ect.

It is always so much fun having oddball problems like this to find. Hopefully I will get some time this afternoon to check it further.