DIY - Custom short shift kit for TH8a or TH8rs shifter.

Here is another DIY mod, this time for the TH8a or TH8rs shifter from Thrustmaster. It is a short shift kit using cheap automotive grade universal shift knob. ****I did not come up with this, I used ideas from YipZone and from SethFrancis

Cost breakdown: (my total cost $17)
$12 - amazon shift knob (pick your own or use the same one) - Cheap Shift Knob

Roughly $5-$6 for a long M6 threaded bolt (m6-1.0 x 100mm) and six pack of M6-1.0 nuts (they did not have a m6 coupling nut so I am replacing that with 4 stacked m6 nuts jammed)

A pen - specific one chosen because I have it already - free.

Disclaimer - I can not be sure the shift knob you pick will work. I picked the one I did because it was cheap, had multiple inserts to fit different sizes and was silver. It also happened to be hollow so the bolt went all the way up inside.

Tools - drill with large drill bit (drill bit just smaller around than the m6 nuts at the tips) gloves, hammer, box cutter (or sharp blade or scissors to cut the pen), a crescent wrench, and two 10mm wrenches.



First you must remove the old shaft - it had a thread lock on it so it will be tight. Remove the shift knob then use a crescent wrench on the flat sides on the top of the old shaft to remove it. It has normal direction threads so turn left to remove.

Measure the height the bottom of the shift knob needs to be off the h plate by threading in just the bolt and holding the shift knob next to it. **IF YOUR SHIFT KNOB IS NOT HOLLOW LIKE MINE YOU WILL HAVE TO CUT THE BOLT LENGTH** Then compare how far in the insert will thread (got it wrong twice forgot to check 7th gear slot first time, then did not measure for the extra depth the insert threads into the shift knob the second) The location of the bottom of the plastic insert is where the bottom nut of the 4 jammed tightened nuts needs to be and marked with fine point sharpie. Again, make sure to measure based on how deep the plastic insert goes into the shift knob.



I had to drill out one of the plastic inserts to be slightly too small for the m6 nuts. This is what the glove is for to protect my hand while holding the insert as I drilled it out. *The plasic insert goes on the bolt then I thread the nuts on the bolt and jam locked them into place (jam locking is tightening them against each other with two wrenches). I then used a hammer and one of the 10mm wrenches to force the plastic insert onto the m6 nuts that were locked into place on the m6 bolt. *sorry no picture of this process* Put one of the extra nuts on the end of the bolt threads and thread it on to protect them, you do not want to hit the threads with a hammer. The M6 nut edges are sharp enough to cut into the insert so that it it solid and the insert does not turn - that is why the insert was only drilled out so far that the m6 nuts would only fit with brute force.





Cut the plastic pen tube to be too long for tightening down the bolt into the shifter. Then slip it on and tighten the bolt down into the shifter without the knob. Verify a good amount of threads are in, but do not bottom out the bolt in the shifter as you want some room for adjustment here. The bolt x-head top made it easy to tighten it down against the pen tube so it was snug.

Then remove the bolt(shaft) from the shifter, set the plastic pen tube aside, and jam the two extra nuts together on the end of the shaft and put a wrench on them so you can hold the bolt securely while tightening down the knob on the plastic insert. The knob should get tight but do not over force it, the insert is just plastic. *sorry no picture of this process* My shift knob goes pretty far over the plastic insert - that is were I messed up the measuring as the shift knob bottom edge would hit the h gate plate and I could not put it in 7th or reverse.


in this image it was actually my second time of not having enough thread length, as you can see there is only a single red line from the first measuring point. In the end there were two red lines sticking out

Now put the plastic pen tube back on the bolt (shaft) and thread it back into the shifter until it is snug against the pen - Tight enough that it won't turn from normal use but not so tight you smash the pen. If you care the orientation of the knob you can cut the pen tube shorter to get this correct.This is why I said to leave it a bit long as there is no need to completely bottom out the bolt into the shifter just get it threaded most of the way in.



Double check that you can get into 7th gear and reverse without the bottom of the shift knob hitting the H-Plate. Cut a new pen tube if you made it too short. Find the sweet spot pen tube length to get the knob strait and the bolt/shaft snug and you are all finished.

The only improvement I need for mine, the pen tube I chose is a little soft. You can see in the very first picture of the completed kit, the bottom is starting to flair out inside the shifter. I raced with it for a good while this morning and it did not budge so for now it seems to be working fine.

Have at it and enjoy a better shifting feeling and a beer..