Hi I have two TA back Home a very nice 85 That I find out came with a six Cil but Now has a 305 TPI Because of this the speedo is a 85MPH I also have a parts 89 GTA with a 350 TPI this have the 140MPH Speedo. I need to fid out how to make the 89 to work in the 85.

I already tried swapping them once first problem was the 85 have the speed cable from the transmission to the gage, the 89 does not it appears to be electric somehow. so I'm thinking I need to swap something else for it to work

The second problem is that when I put it in place the other gages didn't work I'm Guessing their is repining involve for it to work.

Does anyone have tried this? I really Like to have the functioning 140MPH Gage and the illumination of the GTA Gage is better looking.

 

All 85's had the 85 mph speedometer, not just because it was a six cylinder originally. To put the cluster in from your 89, you have to rewire the pins in the plug that goes to the back of it, because the other gauges are in different spots, and the printed circuit is different. You need to buy a VSS (vehicle speed sensor) for the transmission at the tailhousing where the current cable goes into, and run wires to an aftermarket electronic 'brain' that reads the signal and sends it to your speedometer. It's a pain, but doable. Use the site's search function and you can find some good threads about the process.

Welcome to the site, btw.

 

Thanks very much

 

Rather than using your efforts to try & re-pin the dash - why not just take the entire dash housing out of the 89 and install it into the 85. If possible - use the complete engine harness from the 89 in the 85 as well. That way any wiring differences would be minor.