I have a 1994 f350 7.3 turbo diesel and i just changed my transmission fluid and not my rpm needle doesn't work and my OD light is on. When i come to a stop its sluggish to pick up speed. My transmission isn't leaking and the dipstick shows its full. Accepting any help and advice thank you.

 

welcome to FTE. the tach problem has nothing to do with the trans fluid change, but it is why your trans is not shifting properly.
the trans needs both tach signal and vehicle speed sensor signal to work properly. with the tach signal missing, it is in limp mode. try not to drive it too much before you get it repaired.
first thing i would do is see if the tach sensor is plugged in. it is the large nut on the driver side of the top of the timing cover.

 

I think the problem is that the TCM (Transmission Control Module) isn't getting powered up. That means the transmission will always be in fourth gear, so it never shifts and will be VERY sluggish from a start.

This usually happens when the EEC Power Relay fails.

 

yeah whenever the od light remains on (and it's like half it's normal brightness compared to when you cancel od) it means there is no power to the TECA and like Mark states,high gear starts and that's why she's so sluggish.also definitely follow tjc's advice about not driving the truck until you fix the issue.it should be a very easy,couple min,quick fix.
once you power up the TECA again,the tach will also work again too.

why did this happen exactly during a trans fluid change though? odd.coincidence? disturbed bad/bare wires somewhere perhaps like up around the bulkhead connector?
personally i would inspect the wiring and if you only find a bad relay or blown fuse, then replace and just run it and write it off as coincidence i suppose until/unless it happens again lol!






hmmmm.
you know what.be sure to inspect fuse U there.if U blows,so does the TECA relay power and when the TECA power goes,so does the tach.
what makes me think of this is,perhaps you bumped and or disturbed the fuel filter heater wire? notice any shorts in that? it's the very top wire you see at the filter head ok.did you bump that when reaching down in,or with the trans funnel or the like? recall hearing a click (fuse popping) and or seeing a spark? blow fuse U? bare wire to this heater element? is the fuel filter connector wet with fuel and shorting?
i think of this wiring getting disturbed and blowing fuse U as it would explain all the symptoms and it's near the work area of the dipstick tube.it's just a guess but worth inspecting as it's free and you can't beat free fixes.....then change the fuse once fixed if it's blown.
keep us posted will ya? good luck.

if you want,you can eliminate this line (cut and cap it off over by the power distribution box.) trace it over towards the box and you'll find a clip.a good place to remove the wire so it dead ends inside this clip.
(both my trucks got this treatment.) then if you want a filter heater power wire,run your own off a fused relay on a devoted circuit.not off the power line to vital trans operation lol! ford brain fart there (cost is all.)