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So ive got a buddy of mine who has a 1983 Chevy c/k with a turbo 6 liter swap with a 4l80e transmission. The truck is on holley terminator x max with current performance integrated harness. The truck speedometer reads all over the the place on the dash and the truck shifts through all the gears down shifting and up shifting when literally going maybe 10 miles per hour. What in the heck is going on?
Take a log and watch the VSS. Sometimes the VSS will register a large spike for holley systems. Shifting is based on speed input, so if it registers a high speed it will immediately bang into the appropriate gear before dropping back down. If you do see it, then solder in a 10k ohm resistor across the two VSS wires
It's a little quirk that happens on occasion with holley
Take a log and watch the VSS. Sometimes the VSS will register a large spike for holley systems. Shifting is based on speed input, so if it registers a high speed it will immediately bang into the appropriate gear before dropping back down. If you do see it, then solder in a 10k ohm resistor across the two VSS wires
It's a little quirk that happens on occasion with holley
thanks will do
Last edited by Tommy42088; Dec 22, 2025 at 01:18 PM.
I had the same thing happen, although it was not with a Holley. Bad VSS sensor caused the transmission to downshift.
Lucky my 4l80E controller has an optional touch screen shifting option, so I was able to make it home at reasonable speed by manually shifting from the touch screen.
I had the same thing happen, although it was not with a Holley. Bad VSS sensor caused the transmission to downshift.
Lucky my 4l80E controller has an optional touch screen shifting option, so I was able to make it home at reasonable speed by manually shifting from the touch screen.
this is a fresh build, everything is un tested and this is the first bug we have came across. How was your able to come to conclusion it was vss sensor.
this is a fresh build, everything is un tested and this is the first bug we have came across. How was your able to come to conclusion it was vss sensor.
No VSS feedback to the ECU is a pretty good indicator of VSS fault
My touch screen said I was going 0 miles per hour, even though I was moving.
Swapped in a new sensor and never had an issue again.
BTW, if you get stuck and need to get home in an emergency, you can unplug the 4l80E connector and that should give you second gear.
we will look into that as well and see if thats maybe the issue and honestly its hasn't been driven far enough for that to even be a concern. Its just his toy, plus he had a 3500 HD and a car hauler and myself along with a few other buddies all live fairly close so we could easily pull it home, the truck was a full restoration its been down a few years and finally getting to the point where its almost ready for the road. We experienced alot of bugs with mine and many break downs so trying to avoid that this go around.
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Transmission going crazy 
