what would it take to use a 140 mph spedo cluster from an 87 or 88 gta in my 85 t/a both cars are tpi 5.0 if that makes any differance.

 

Engine size doesn't matter.

Your 85 has cable driven speedo and the 87 and 88 are electric. You'd need the newer VSS sensor that goes into the back of the transmission and I'm sure some other misc crap to let the car know how fast you're going...

 

I read in another post (somewhere) of a box that would convert the speedo cable to a VSS signal. Dakota Electronics or something.........

 

you will need this box that goes between the tranny and the cluster,

 

I installed the 140 cluster in my 85. You will need an electric sending unit and a buffer box( yellow box). The problem is that the two connectors on the cluster are wired differently. You will need to cut and splice the traces on the curcuit board so they go to the correct location. I use a Dakota Digital box to correct my signal because I did not know what gear I had in my tailshaft when I installed the T5. If you have the correct gears you wont need it.

 

I have an 85 T/A and i put a 87 guages in but it didnt work, i had the spedo working on the bench when i i wired it up with the yellow box and the VSS, but when i put the guages in my car i didnt even hook up the yellow box i wanted to see if the the fuel, volts, oil, and temp worked. Every thing went to zero or maxed out and the spedo acted like the tack, im sitting the idling and the spedo is boucing around and the odmeter is rolling foward so ami going to have to hunt for some wiring diagrams to switch all my wiring to run this dash in my car???

 

Like I said- the two connectors on the cluster are wired completly different. If you compare the two clusters you will see the volts, oil pressure ect.. are in different locations. Map out were each pin on each connector goes then make the connectors on the new cluster do the same.