The Fairwater Collection !

An MGBGTV8 Sebring and some interesting Land Rover conversions.
Now, see also my professional site at: www.met-alchemy.com !

MG Page 4. Tunnel Modifications for the LT77 Gearbox. 9th and 10th June 2008.

To fit the LT 77 gearbox, some modifications are necessary to the gearbox tunnel, as the LT77 is somewhat taller than the standard GTV8 gearbox.  These are not extensive, but are just a bit of a bind.  Several ways have in the past, been designated, including making a box for the top of the tunnel.  This is not how I have done it, prefering to use existing metal persuaded to take a slightly different shape by means of a sabre saw and big hammer! The idea is to reshape the top of the tunnel so that the section in between the two big brackets on top of the tunnel is level with the rest of the tunnel to the rear of the brackets, rather than sloping downwards towards the front of the car, as it is constructed. The width of the level section required is not too wide; about three inches only.

The first step was to make a saw cut in the position shown below, through the curved edge and extending as far forward as the saw will allow, but not down the sides any more than can be helped. The idea is to be able to get the saw blade into the cut from the other side, so as to draw the cut right across the width of the top of the tunnel.

(9th June 2008)

Extending the cut right to the other end, is shown below, by inserting the end of the blade into the above cut from the other side, thus. Yes, the blade will cut round corners as shown here, so the body of the saw does not need to be in line with the cut line.

After slicing the tunnel right in front of the forward bracket, you also have to take out the centre portion of the rear bracket, like this. Firstly cut across the back corner to make a slot, as below.

And then from the front, take it out like this.

This spot welded seam seen going straight across the top of the tunnel below, downstands at the connection between the bulkhead and tunnel, and has to be removed to gain clearance.  The downstand also incorporates the bottom of the rear bracket inside the car, which we have  now separated in the first action, from the tunnel.  The tunnel can then be persuaded in an upward direction.  Note the hammer already waiting underneath!

First lazy attempts were made with a jack, as below, hoping that this would push the tunnel up.  It didn't.  It just lifted the car up without any deflection of the tunnel at all.  Back to the hammer then.

This is the underside of the tunnel looking forwards.  The tunnel has been hit comprehensively behind the slice made in the first picture, which separated the tunnel top from the seam at the bulkhead join.  This downstanding seam can now be seen below... errr downstanding.  The new tunnel shape has gone up above the soffit of the bulkhead in front of the seam, by about a quarter of an inch, to give some reference measurement.  The next stage is to cut off this down stand with the sabre saw, which will separate the front section of the tunnel from the vertical bracket which this downstand forms a part of.  That front section of the tunnel as part of the bulkhead, can then be hit and dressed upwards to meet the new shape of the rear section of the tunnel, as following pictures will show.

Below: downstand seam still intact.

(All below; 10th June 2008)

And there it is: gone.

View from the front with the seam cut out, below.

Now then, below we can see that now the front part of the tunnel which forms the bulkhead has been severed from the seam by cutting the seam off, we can also dress this upwards too, to meet the same shape as the rear part of the tunnel previously re-shaped.  This produces a new vertical section as can be seen below, which can also then be cut off.

 

Leaving a smooth tunnel, like this:

All that is now needed is a nice seam weld across the joint, below, seen from directly underneath.

Final look from the front is as below.  You can see where the seam used to be, and about an inch of headroom has been gained here.

Finally, here are the two pieces which were cut out, posing with a piece of bullhead rail!

It has to be said at this stage that while I believe that the extent of work outlined here will be sufficient, at the time of writing it is unlikely that I will be able to prove this until 2009 when it is envisaged that reassembly will take place. 

 

 

Fitting the LT77 gearbox to the car.

Actually it was November 2010 when the actual installation was undertaken.  How time flies.  Fitting the gearbox to the engine and getting a clutch that works is reported on the final assembly page, but here, physically getting it into the car to a working state is covered.  

I can in any case report that the modification described above has worked.  On first examination it would appear that when the crossmember is attached to the bottom of the gearbox and then bolted up to the chassis rails, the top of the gearbox was touching the tunnel in one place, that being the plastic breather cap.  This was before the fitting of the central gearbox mount, which screws up and tightens down the two flexible angled rubber mounts on each side.  This gains about half an inch of clearance at the rear of the gearbox, which will translate to clearance at the front end of a good quarter of an inch.  Should any more be required, then it is feasible to space down the crossmember a bit as necessary.

The crossmember itself has to be relocated, due to the gearbox  mounts being a bit farther back than on the original gearbox.  In practice, it is possible to use one of the rear set of holes for the front holes on the crossmember, which is useful, and this  means that only one new set of mounting holes and fixings have to be provided, for the rear of the crossmember only.  As this is mounted on box section, it is best to either install a rivnut or cut a hole large enough to accept a suitable nut, which is welded onto a small piece of plate, which is then in turn, welded over the hole with the nut inside.  I actually chose to open out a hole in the floor above, and let in, a longer bolt with a nut installed such that when inserted, this nut is bearing on the base of the box section inside, and the head is just protruding above floor level, which will be covered by carpet.

Tail of the gearbox showing mounting points.  These will fit the MG standard crossmember, but the crossmember is a bit too far forwards.

18th November 2010

See, a bit too far forwards.

New fixing to the left, (rear), and original fixing (which used to be the rear fixing) to the right, or front.  The now spare set screw is fitted to another intermediate hole, as two pairs are provided.  I would however, recommend fixing this all up at the end, with the gearbox in place, so as to get it right.

This is the centre gearbox mount.  The lower half is standard MG.  The top half is a piece of inch and a half square x 3mm box section.

Finally all fitted up together with the remote.

 

Inside, the gear lever comes through the tunnel slightly farther back than original, and slightly to the driver's side.  The cover plate can be seen refitted in its new position.  The old fixing holes can be seen to the bottom and left of the plate.  A corresponding amount had to be cut from the tunnel aperture at the rear and slightly to the driver's side to allow full stick movement.

There is no issue with fitting the console back in place.  It can be repositioned satisfactorily and there is no noticeable difference in the way in which it looks.  You cannot tell from inside, that there is any change.

In the floor behind can be seen the new mounting point going through to the gearbox crossmember.

 

Finally the stick itself was modified, both for length and to accept the original V8 gear change knob, which I happen to like, in a 70's Leylandish sort of way.

The SD1 one is tapped M12, and the MG one is 3/8" UNF.  Non compatible?  Well actually I converted the thread, firstly by running a 7/16" UNF die down the shaft, and then following this with the 3/8" one.  Sharp intakes of breath all round at this bodge, but as you can see from the below picture of the finished article, it has worked perfectly and the profile of the shaft is almost identical to the original one.  I then chopped about half an inch or so, of length off it and it is all fine.

28th November 2010