Fellow Gear Heads, does anyone know what gadget I need to get my speedometer working again after a 4l80e swap? Car is a 89 trans am and had the 700r4 originally. Thinking the device needed is some type of splitter that allows the cars computer to communicate with the transmission computer correct? Fairly simple thing if I remember right. Just can't recall the name of the part.
Thanks for any help.
Gb

 

Dakota SGI-100BT

 

The 4l80e doesn't have a TCM built in. The controller for the transmission will be in the ECM itself. You need a Dakota digital box to send the VSS signal to there then off to your speedo

 

Appreciate the information. Forgot to mention, I purchased a controller from Painless, so the 4l80e does have its own tcm. The engine computer is also from Painless. After doing some more research I found that what 4l80e swappers need to keep the original speedometer working is a VSS splitter harness. Current performance.com makes one and it sells for around $38.00. The Dakota box would probably work also but might be overkill for just needing to get the speedometer working.

 

I've got that exact same splitter harness on my 4l80e. For whatever reason the speedo output on my Dominator ECU doesn't work with my autometer speedo. So I have to split the signal and go straight to my speedo

 

So the VSS splitter solved the issue then? Can a technology challenged hammer mechanic like myself wire up something like that without too much trouble? Probably doesn't include installation instructions.

 

Yea the splitter was the answer. Holley swears up and down that you cannot split those two devices but I proved them wrong. You should be able to just plug it in and go

 

That's good news. If it's a plug and play setup then that's even better. Prefer not to have to splice into wires. Appreciate the feedback. Glad you got it working.