4L80E Question: Electronic or Gear Drive Speedometer. Which is best.

chris kirk

Active Member
Which application works best to connect the speedometer using a 4L80E transmission in an '87 GN, a gear drive or electronic speedo. It doesn't have to be the cheapest way but it does have to be the best. I know the gear drive is an extra $550 but that's not going to change my mind if inevitably it's better. I was told the electronic speedometer would be the best way and it would connect to the shift controller. First hand knowledge would be greatly appreciated.
When I used the 4l80e, the TCI/Fast TCU box didn't have speedo output that I remembered, I just clipped onto the speed sensor on the driver's side of the trans (rear of two?). I used both a VDO speedo and then a Racepak dash - either worked fine.

There is a company that also makes a box and basically reads the speed sensor pulse and has an electric motor that drives the factory type speedo cable. I didn't try that but it was surely appealing if you wanted a clean factory look.
Just to answer this incase someone else pulls this thread up in the future, the current TCI ez-tcu has a speedo output signal that can be easily tapped into the factory digital dash, you still lose your odometer though. Your other options are like you mentioned, a gear drive tail housing (jakes performance), an electric to mechanical cable converter (TCI), or you swap your gauges to an aftermarket electronic speedo. They all have their pros and cons.