The connection between the the gear lever and gearbox is 2 cables, one cable for the side to side movement and the other the back and forth movement. This should be easy to check by disconnecting the cable at the gearbox end and seeing if the movement is still stiff.

If it is the cable that's causing the issue it's better than having to dismantle the gearbox but I believe they're a pain to change although I've never done one myself.

 

Thanks for your reply, I really appreciate it! Ok yeah, from what you've said, the cable seems like the most realistic reason.
This being my first ever car and only for a few months at that I'm still learning as I go along - how would I go about disconnecting the cable at the gearbox? Is that something easily done or am I better to wait until I find someone who knows what they're looking at?

 

Take a look at this video, I'm not sure if this is the for/aft or side to side cable, the second cable is above it and to the right. It should also be noted that there should be a rubber gaiter, that's missing on this car, that covers the inner cable where it exits the outer sleeve

 

I should have mentioned that the video shows an F, the TF setup is slightly different I believe but the cable ends are the same.

 

This is great stuff, I will have a look at that tomorrow morning, thank you!

Something I just remembered, the last time I drove the car before it seized up yesterday which was about a week ago, it suddenly started rattling from behind. It was definitely coming from the engine area and every slight pothole increased it dramatically. I decided to finish driving to my destination as it wasn't far to go before looking at it, but suddenly just heard a 'clonk' and a rattle as if a screw had fallen onto a metal plate, and then everything was silent again. It got me home ok and as I said above it got me 5 miles from home yesterday but I wonder if that has anything to do with it?

 

There is a metal clip holding each gear shift cable to the bodywork just before the bellcrank. These clips apparently can come loose. That is enough I understand to cause difficulty changing gear. If only one clip came off, that could explain why you've lost the gearchange in the one direction only. Could explain the rattle too.

The good news is the fix is to simply put the clip back in place.

 

I have since had my car repaired and thought I might close off this thread with the solution. In my case, it was the gear linkage that failed. I have only had the car for a few months but I have a receipt for way back in 2006 for an MS Slick Shift. It lasted a really long time but ultimately just had enough by this point.

I will upload a picture to make it easier to understand. Basically, the up and down movement was restricted because the two metal parts were rubbing against each other. Apparently, there is meant to be a washer separating the two, but because it was made of copper it ultimately cut through the aluminium and the two parts ended up side by side. (I haven't yet checked if this is true, this is what I was told). So now we have the original gear linkage back in, I kind of miss the Slick Shift and am happy to see MS still makes them so I might reinstall one when finances allow.

As you can see in the image, left to right movement was fine, but the red arrow is pointing towards the two parts that should apparently be separated to allow a free up and down movement.

Thanks again everyone for your advice!

 

Any idea how many miles the car has done since 2006?. The first time that I have heard of this cause.

Transmission tunnel off I guess?

 

About 40.000 miles. Not sure on the transmission tunnel, as I'm not even sure what exactly it is sorry 😄

Honestly, I was very surprised myself, as I've only heard good things from MS - but I asked to keep the slick shift and it really is incredibly stiff so that was definitely the problem, although maybe the explanation of the problem is wrong. I will have a play with it at some point this week and if something changes will update.

 

The reason given could well be right. I am surprised that a copper washer was used.

 

Yeah I've got a great mechanic nearby who I trust completely so I'd be surprised if it wasn't the case. Still very odd but there you go.