Replace/rebuild rear caliper?

Try pulling the pin that connects the p brake cable to the caliper.   A simple check to verify that the cable isn’t causing the drag.

Once I pull the pin, what do I check? If the mechanism moves freely? How easy is it supposed to be to move? 

You want to check that the cable is moving freely and not frozen.  Hard to isolate the cause when its connected to the caliper. 

I will do so later this week for sure, thanks guys. I'm not buying anything till I've finished diagnosing. 

Cable definitely causing the drag. Punched the pin out and the caliper's handbrake assembly popped back into its neutral position. Cable moved the first pull but didn't budge the subsequent ones. Not broken, since it's moving and causing drag... but what could suddenly cause it to start dragging? Maybe needs adjustment on the center console side? Thoughts? 

My cables started sticking, but would free a little after driving.  By pulling gently on the brake handle, I could feel if there was loose play, indicating that the cables were tight and dragging on the brake.  For a while they would “reset” after driving.   I decided to extract the cables and see what was going on.   Holy crap - they were very very very tightly jammed in the cable housings.   I used a spring compressor threaded rod rigged backwards to pull the cables out of the housings from the back.  (First unsolder the tip at the brake lever).   The cables have a plastic sheathing melted (?) to the steel cable. I burned off the plastic with an oxy torch.   Reinastalled them, and reattached the tips at the brake lever.   Tada.   Free fix....only took me about 5 hours!!   I’ll dig up photos.

I tried all sorts of motorcycle cable pressurized sprays prior to ripping the cables out.   No joy.   Nothing can soak between that plastic liner.   It’s debatable whether my (fix) was easier than dropping the gas tank and just replacing the whole cable.

I made the replacement tips from some hydraulic line fittings.   They were just the right size.  Actually I think one picture was trial #1, because my homemade tip is 90 degrees off!  Cable goes in the side, threaded bolt goes down the center.    

I went to all this trouble because my 2GR swap uses a pneumatic brake booster in the clutch system.  No boost until the engine is running, so it’s hard to get the car out of gear when parked.   I leave the car in neutral with parking brake engaged, so parking brake is critical for me.   

I remember reading your thread cyclehead! But your expertise is far beyond mine in terms of your handiwork. Luckily I have a brand new OEM cable laying around waiting for this day to come. Bought it years ago knowing it would eventually need to be replaced. Good thing, back then I was doing alright and now I'm a bit broke haha. I'll likely just replace it even if it is a colossal pain to drop the fuel tank.

Mine has been dragging for a few drives, never freed up no matter what I did. Brake would smell after a drive. It's toast. But I'll keep the old one around, might do this mod eventually.

If it wasn’t so hard to pull the seized cable out of the housing, it would be a simple fix.  We need some clever entrepreneur to make a threaded extractor tool from a piece of all-thread.  The homemade tips are easy to make.  And the “fix” works!  No more seized cables....   Actually, a piece of 1/2” electrical conduit, a length of 1/4’ allthread, nut and washer would just about do it.  Maybe weld a nut on the end of the allthread so you could spin it with an electric impact tool.

Posted by: @cyclehead

If it wasn’t so hard to pull the seized cable out of the housing, it would be a simple fix.  We need some clever entrepreneur to make a threaded extractor tool from a piece of all-thread.  The homemade tips are easy to make.  And the “fix” works!  No more seized cables....   Actually, a piece of 1/2” electrical conduit, a length of 1/4’ allthread, nut and washer would just about do it.  Maybe weld a nut on the end of the allthread so you could spin it with an electric impact tool.

It sounds like a new product may soon be added to the line of amazing products available only from Cyclehead Design Studios.  

Send core in, get fancy working cable back. Could charge $$$ since OEM cables are so expensive.