IRS Conversion - part two

24th March 2008

Previously in the last article I have cut away the body to allow access to install the IRS brackets which are part of the IRS conversion. I had downloaded the Internet article at http://bajaclub.co.uk/PDF_Documents/IRS.PDF from Airsouls. Although this article was written quite well it did not adequately explain the process of cutting in the brackets. As this is the most important part of the IRS conversion this was something that I would new to spend time over.

The first thing which was obvious about the installation was that I would have to either buy; make or borrow a jig that would give me the proper position of the IRS brackets. Fortunately after placing an advertisement on Vzi I was soon in the position of two IRS jigs. One thing I have found with using other peoples jigs is that as you haven't made the jig, its really important to ensure that you know how it works and more importantly if it does.

I decided that I would have to try the jig on a 1303s chassis to ensure that the jig was correctly aligned. It was noticeable straight away that 1303s brackets where different to the ones that are available today. The other obvious difference was that the frame horns seemed to be a different shape . The jig fitted into the IRS brackets on the 1303s chassis . The noticeable thing about the jig on both sides was that the tube that was attached to the end was short on both of the jigs. The reason for this was that the jig would not be able to fit into the bush on the furthest end of the bracket if it was any longer. I returned home happily in the knowledge that the jig was ok and a reasonable fit.

It was at this point that an child hood illusion was shattered. I had always thought that VW cars where superior because they used the metric measuring system way before we adopted it in the UK. When trying to locate a suitable bolt that would fit the brackets this turned out to be 1/2" UNC. Well as you can see the myth was not true.

I took the jigs back to the garage. The first thing I needed to do was to cut away the metal where the bracket fitted into the frame. You can see in the pictures I started by removing material from the flange that braces the frame horn to the torsion tube. I took the material away to the handbrake cable guides. I new I would have to remove more material and take the flange back further before the bracket would fit in and not foul the IRS Arm when it was in place. The next thing I was going to have to do was to use the jig to locate on the bolt hole on the side of the frame arm. To do this the jig would have to be placed on to the car.

I needed to remove more material from the flange on the frame horn so the length of the bracket would fit alongside the frame horn. With the Jig in place on each side the and done up enough for the arm of the jig to make contact with the frame arm. I could use a black marker to draw around the outside of the bolt hole. I then used a Starrett 1 3/4" or 32mm type hole saw to cut out the hole were the bracket protruded through. It is important to note that when you mark the holes you have marked the circumference of a circle.You must ensure you have a centre point of this circle before pop marking and drilling. This can be achieved by using dividers or compass. The hole can be troublesome to cut out as it is very tight to get a drill and Starrett hole saw into you may find that the only way to do this is to purchase right angle conversion for your drill, these are exceptional for getting into tight spaces. The one pictured right came with a key less 10mm chuck for £9.99. I added an £18, 13mm keyed chuck onto it so that I could fit the Starrett arbour which was 1/2" into it . With this hole cut out the bracket could be slipped into this hole and positioned on the rear torsion bar to gain its eventual position. I used this method to locate the position of the bracket on both sides. The main reason for this was that on the Baja club IRS conversion the hole was made too large. Additionally the bracket did not sit entirely in the hole so it had to be cut out precisely. The angle that the brackets protruded from the torsion bar where then compared and adjusted so they where the same, luckily no adjustment was needed. I cut the holes out easily and tried the brackets on each side. I found the driver side (left picture) still required more material to be cut from the flange to allow the bracket to be fitted and marked. This bought the flange under the handbrake cable and would mean that the cable position might need to be changed. It appeared different from the passenger side as it was not interfering with the bracket like the drivers side was.

With the holes cut and the bracket positions marked. The gauge of the metal could be seen easily with the holes cut and looked to be no more than 2mm. I could start removing material from the torsion bar end working towards the rear of the car. This was going to be a slow procedure of cutting a strip back then trying the jig and bracket in place until a good fit was made. I would start by removing half and then use smaller increments on each cut back. I new the end of the bracket was supposed to sit outside the frame arm thankfully to a picture in the Airsouls article on the bajaclub website.

Once the brackets where made to fit, the jig and bracket where then fully done up in preparation of the brackets being tacked in place. Before they where tacked in I went back and took more measurements of the original brackets to ensure everything was in line and in place. When I tried to get my Arc welder running on my Honda Generator I soon found that it drew too much current from the generator to weld with. I would have to hire a welder generator for machine hire company to allow me to get the brackets welded in and the new A Arms fitted.

Cont.

Removal of the AB Gearbox in preparation for the AT box .

9th march 2008
The proposed IRS conversion was going well I had the A-Frame Arms ready to be fitted to the chassis. I had bought a 1302s IRS gearbox with AT code that had a higher ratio drive as it was originally made for a 1600 engine. This would better suit my engine. I had bought brackets to fit the IRS arms on a visit to the new SSP/VW heritage site.The brackets would need to be cut into the chassis and welded onto the torsion tube. To make way for the brackets to be welded into the chassis the gearbox would have to come out.

The removal of the gearbox is something best done with two people. I must thank my friend John for his help this morning. The removal process is quite straight forward, it is not necessary to remove the brakes from the drive shafts, however the brake hydraulic lines must be removed from the slave cylinders and the handbrake cables must be undone at the handbrake. I have already removed the drums as I wanted to lose the weight from the gearbox, additionally I was intending in replacing the drum brakes with a rear disk conversion. I had also removed the flexible hydraulic lines at this time.

Before undoing the gearbox bolts you need to remove the three bolts that hold the lower part of the drive shaft to the drive shaft. These are torqued up so you will need to use quite a lot of force to get them undone. You can use a length of tube on the end of a socket wrench, but in practice they can be undone with two 19mm spanners. With the three bolts undone you can unclip the rear bump stop. This will allow the drive shaft to separate from the swing axle. With the three bolts undone you must ensure that you have no cables or wiring attached to the gearbox. This usually comprises of the reversing light switch at the front of the box, the starter motor wiring and the clutch cable. You will need to release the gear linkage where it is connected to the gearbox. This is located under a small cover plate behind the rear seat and is secured down with a small Philips screw. With the cover plate off the linkage will be exposed. The linkage is secured by a 9mm square bolt that goes through the linkage, it may have a locking wire securing it which will needed to be cut off. With the bolt removed the linkage can be separated from the gearbox. With all these items removed you are ready to get at the gearbox bolts.

The front gearbox bolts are situated on and below the torsion bar tube in the centre. The two bolts can be undone with a 19mm spanner. The rear gearbox bolts are 27mm and you will need to get the proper spanner or socket to get them out. They are also torqued up to 166ft/lbs and will need a large amount of effort to get them undone. With all the bolts removed the gearbox can be pulled backwards and out of the car. You must first pull the drive shafts from the swing arms and then with a friend get a good grip on the box and pull it backwards. The gearbox will come backwards out of the rear arms. Be careful as it comes out as its weight will increase as its manoeuvred out and the gearbox is free. You will also find it quite awkward as it shifts out . Ensure you both have a good grip and be careful not to drop it.

With the gearbox out it is noticeable that the front mount on the new and old gearbox is different. The AT gearbox has a 1302s mount which has three bolts on the gearbox. The AB box has only two. I would have to swap the front nose cones from the two boxes.

With the gearbox removed it is noticeable how far the battery box comes down . I would have to cut this back and re fibreglass a new base in the box higher up.

It was also noticeable that the area that the IRS brackets would be quite difficult to cut into the chassis with the body on.

I was beginning to wonder if this was the best opportunity to have the chassis Zinc hot flame coated. With the chassis out the welding would be easier to do as I could weld up the IRS brackets on my drive way before taking the Chassis to have it blasted and zinc coated. This would also allow me time in the garage with the body of the car to re-fibreglass the underneath.

Preparing for the IRS/Gearbox conversion

6th March 2008
The garage was starting to fill up before I started on the stripping down of the back end. As the gearbox was coming out to be replaced by an IRS 1302s version, I stripped down the brakes to make this removal easier.

The removal of the wheels and drum brakes where fairly straight forward. The wheel bolts where loosened whilst the car was on the ground. As when the car was to be put on axle stands this would be easier to get the wheels off. Once the wheels where off, the drums where visible to be removed. These are secured with a cotter pin and large nut. The nut is torqued up to around 250ft/lbs so you will need a long bar with the handbrake latched on before it will budge. With this nut off it is best to back the pads off. These are retracted by rotating little star adjusters which re hidden in the back of the backing plate by two rubber bungs. You can rotate the star adjusters with the correct tool or a medium sized flat blade screw driver. Turn one at a time to ensure you are not winding them the wrong way and locking the brake up further. With the brake pads backed off the drums can be withdrawn from the shaft. Personally I use a long socket-set extensions held horizontally against the drum and between the backing plate. This can then be hit with a hammer to remove the drum. It is sometimes necessary to move the bar to the other side of the drum so that the drum comes off evenly. The backing plates must have the handbrake cable unhooked. This can be achieved by undoing the nut at the back of the plate that bolts the cable tort. Releasing this gives enough slack for it to be unhooked. The brake cylinder also needs to be disconnected and sealed up.The backing plates are held on by four 14mm bolts with these removed the drive shaft bearing cover plate can be removed and then the backing plate will come off. I placed the drive shaft bearing covers back on so that the bearings would be sealed.

Removing the the shock absorbers was just a case of undoing the respective bolts and removing the shock absorber. It is interesting that the only difference between the IRS and Swing Axle shock absorbers is the wider bush that sits at the bottom of the shock. The bottom bush can be removed by driving in a new one. I had removed the longer bushes from an old set of IRS shocks that I bought with the IRS parts.

You can clearly see in the picture right above that there would need to be some work with the fibre glass body sections to allow the IRS A-Frame arms to travel in their plane without hitting the body work.

I needed to get a friend to help me remove the gearbox as this was a heavy item that would need to be balanced on the jack whilst it was being undone. I would attempt this when a friend was available.