I've recently gotten my truck (1994 5.0, 4r70w) back on the road. I've only ever driven short drives in it. I took it out on a long drive (few hours) and I got a blinking o/d light...

I tried to pull a code but nothing is stored. I haven't been able to pull the code whilst it is blinking, as it stops blinking after a bit, sometimes 1-2 miles later. Always resets after restarting the truck.

Truck behaviors:

1)Really harsh shift 1-2.

2)Seemingly delayed shift into O/D but without a tach this is hard to tell. Also having never driven another 5.0 auto I have no comparision. The truck is very slow so this may be how it is supposed to be...

3)Light seems to, more often than not, blink under stress. A steep hill (not every steep hill) or a WOT 1-2 shift can also provoke it. It only happens when the truck is warmed up after a solid drive.

4)It also blinks more often (will turn off and then on again later) on highway driving stints over 65mph.

I do not think it is an overheating issue because I had it pop up doing 25, and not pop up running a VERY steep grade. Saw it pop on coasting down a hill (could have been delayed from the prior uphill). The main reason I do not suespect heat is that it sat for 15 minutes (truck off) and I did a WOT 1-2 shift and it blinked for 5-10 seconds before it stopped. Did it 2 WOT shifts in a row. No way the tranny was still overheating as it was not blinking when i parked.

Truck behaves no differently when the light is blinking, so no limp mode. O/D works fine. No slips or TC shudders either...

Any thoughts without a code? What part number is the shift solenoid, I'm thinking its for that...

 

is it blinking a series of blinks indicating a number?

hows the level of fluid? is it burnt?

 

No, it just blinks consistent. Fluid is good and clean (pulled pan and replaced filter and fluid a few hundred miles ago. It is bright and no burnt smell.

I've just now noticed the light blinking. It could have happened in the past but being that the light is on the shifter not the dash it is easy to miss. Also seems to only happen after the fluid was good and hot, hotter than even a 10-20 mile drive gets it. In the year I owned it the truck never left town and the prior owner said it was just a town round around too...

If i do the KOEO test I pull no codes, and since the code clears when the engine is shut off I can't initiate the test to pull a code...

 

Correction... I have done the KOER test. I will look into the KOEO test...

 

your not supposed to do KOER until KOEO gets a 111 system pass...that light also serves as the trans fault code light meaning there is a problem in the trans somewhere if the fluid is clean and full i would take the truck to a professional for further diagnosis

 

I pulled a 111 code but I'll read up on the test more...

 

Ok, did the KOEO test instead of the KOER test and i found my trouble code:

452 - Computer detected an error in the VSS or PSOM signalduring the last 80 warm-up cycles...

Thoughts? Transmissions are my weakness. Is it safe to drive with this issue or am I risking damage? Could this be messing up my shifting?

 

I just went ahead and replaced the sensor. 20 bucks. Hopefully that cures the issue. Everything seemed kosher upon a short test drive. Drove and worked the exact same. I'll see on my 7 hr drive from Pittsburgh to Charlotte...