Ls400 Towing Eye – How Does It Fit?

Colin M · June 12, 2015

According to my Mk 3 Owner’s Manual, the threaded towing eye,
which lives in the boot on the near side of the spare wheel under the boot mat,
screws into a threaded hole which is visible through the long (top) slat in the
front bumper. It is at the nearside end of the slat and there is plastic peg
screwed into the hole (presumably to stop corrosion of the thread through
water/salt etc getting into the hole) and the peg needs to be removed by
screwing it anti-clockwise before the towing eye is screwed in.

I thought I would give the towing eye a trial fit on both my
LS400s just in case I ever needed to use it. Being an automatic, I would not
tow the car any distance but if it broke down in a dangerous position I might
want to tow it a short distance to a safer place.

The plastic pegs, which I suspect have never been removed,
showed no signs of movement and there is hardly any room to get your fingers or
any pliers in the slat in the bumper to twist the peg. I eventually managed to
remove the peg on one car using a multi-pin socket i.e. a socket with lots of
small steel pins inside which depress around whatever size nut you push the
socket on and, in theory, enable you to tighten or loosen the nut. Some gentle
levering of the socket backwards and forwards when it was pressed over the
rectangle shaped end of the peg eventually loosened the peg and it screwed out.
Heartened by this, I tried the same on the peg on the other car and the end of
the peg promptly sheared, which meant I had to drill the plastic out.

So far so good, apart from wrecking one peg, and I now come
to screw in the towing eye. But it does not screw in because the thread on the
towing eye is bigger than the hole. I use a vernier gauge to measure the width
of the inside of the hole and it measures 15mm in diameter. I measure the
diameter of the towing eye thread and it is 17mm. I get the towing eye out of
the other car to see if it is the same 17mm size and it is. The hole on the
other car is also 15mm, so neither of the towing eyes will fit in either of the
holes. I have a look to see if I have a 15mm diameter bolt with a metric thread
which I can try in the two holes. I have but only with a finer thread. I do not
screw it into the holes but it is clear that this is the correct 15mm size to
fit the holes. I have taken a picture of the 17mm diameter towing eye and the
bolt with a 15mm diameter.

Is your towing eye diameter 17mm? Have you ever tried to use
the towing eye and, if so, have you encountered the same problem I have?

Any thoughts would be appreciated.

Thanks in advance.

(If you click on the thumbmail, it will show the picture in full)

Colin M · February 20, 2016

Here is the answer to my question.

The towing eye will fit if you turn the thread down on it in a lathe to just under 16 mm (15.8 mm) and then use a 16 mm metric die (with a 2 mm pitch between the threads) to recut the thread.

It fits fine now, as you can see in the photo.