Can the entire gauge cluster from an '85 Trans Am be swapped out for something that goes higher than 80 mph? Do they have the electronic contacts on the back (like plug and play style) or are these cable driven? I'll even take a 120 speedo, I just hate the look of one that maxes out at 80.

 

Not 100% sure about the T-A, but I just swapped the gauge cluster on my '84 camaro last night. I put in a 115mph cluster out of a '88 z28 that I got off of ebay. Very easy to do.

Check out the Tech article (https://www.thirdgen.org/newdesign/tech/gauges.shtml). the only thing I had to do additionally was to loosen the steering column bolts so I had enough clearance to pull out the old cluster. the tech article also says you have to reach up under and disconnect electrical connections, but mine has connections that just 'plug in' when the cluster is pulled out or pushed in.

 

The 85 model had a cable driven speedo, all of the 120 and 140 MPH speedos in the Trans Am/Formulas are electric (unless it's an aftermarket one that was sold before 86) They changed the type of speedo sometime mid year '86, my Firebird had a mechanical speedo, but I purchased a gauge cluster from an '86 LG4 car to get the bezel and it was electric and was an 85 MPH.

 

So, as far as swapping the gauges goes, what are my options?

 

You will probably want to do what I did, I bought a harness out of an '91 Trans Am with the cluster, then something happened to that harness and I got the one out of my GTA to use while I was doing the body work on it.

Any harness from an 87-92 should work, best bet is to find one out of an '87 since the '85 doesn't have VATS and that wasn't done on the Trans Am's until '88

 

just to add to this, VATS was added to firebirds during the '88 production run, so some 88s will have VATS and others won't. It's rare that you'll find one... but my friend has an 84TA that was made for sale in Canada and the speedometer is cable driven and goes to 140 Kilometers/hr. If you have one of these clusters, I think it'd be fairly easy to have someone recalibrate it for Miles/Hr. I suggested it to my friend, but he wants to switch to all aftermarket guages.