Slushbox dying. Replace it or replace car ?
 

It appears my transmission is dying on my 1993 Civic Dx hunchback.
First signs of this was my VSS ( vehicle speed sensor ) going out.
Then my odometer.

The car currently is getting 33 MPG highway versus at the very least 42 MPG that I could get on the highway.

I recently took a trip in which I drove 2/3 the way on a 135 mile trip behind a guy towing a large car carrier trailer. He was doing around 50 MPH the whole time and his trailer punched a huge hole in the air in front of me.
Despite all of this and tires pumped to max sidewall pressure and no A/C usage , I only got 35 MPG.

The car is probably worth around $ 400 in its current state and has around 126,000 miles .

The car seems to shift alright and the speedometer / odometer works for exactly 13 miles at which point I assume the transmission warms up and then fails to shift correctly.

At this point, the speedometer needle becomes erratic and finally drops to zero.

Advice ?

This is a non CVT automatic car , and I had a habit of engine on coasting in Neutral , but at slow speeds.
At speeds higher than 45 MPH the shift was smooth from N to Drive, but under 45 MPH, the engine would rev really high before engaging the proper gear as I shifted back into D.

I fear this may have damaged the transmission.
What do you guys think ? From what I understand, the car is flat towable.

I guess in the end it is up to you, do you have the space, time, tools and ability to swap the trans? If yes, then it can be a great option. I know with my neon that when the motor/trans is done I am getting rid of the car simply because it is rotted out beyond the point of investing too much money and new parts into it. If the rest of the car is great, I say go ahead and swap the trans.

If I swap in a new transmission, it will be a manual.
It will be done at a shop and using a junkyard transmission.
What would be an honest rate for something like that ?

To be honest I have no idea about what the rates would be, sorry.

I would check with some local shops the very question you asked us as the price is dependant on where you live. Go to 3 or so reputible shops in the area and get a written estimate including what they will do. Then choose which one you want to use.
Remember you often get what you pay for. And every once on a while you get a screeming deal that works out.

Have you replaced the VSS? Sounds like some more tests need to be done before writing off the tranny.

If you're having a shop do the swap, you would probably be better off selling your car and buying a car that already has a manual. I can't see it being very cheap. If you could do the swap, though, I say go for it.

VSS has been replaced. Brand new remanufactured part from AutoZone.

The trans swap, if you provide all the parts, is an R&R, which (around me) is $200-$400, depending on where you go.

You'll have to install the clutch pedal and cable/hydraulics yourself, though.

Best to ask around, or check CL. You'll probably find a handful of tuners that have the parts you need and are willing to help you out for a few bucks and a six pack.

So do you guys think I damaged the transmission by EOnC ?