Please Note - Pictures to follow soon.

The gearobox I am using in the Ghia is a Porsche 915 gearbox from a late model 911. The 915 gearbox was introduced in about 1972 replacing the earlier 905 unit and continued in production up until it was replaced by the much better G50 box in 1987.

The 915 box has a regular shift pattern, whilst the earlier 905 box is a 'dog leg' box, which in my mind is a good reason for choosing a 915 box to fit in your VW. Another good reason is that the 915 box is much stronger than the earlier 905 unit, this is especially true of the later models, which have an uprated differential - a definate plus if you're running a high powered motor, some models were even available with a limited slip diff.

You will need to make some changes to be able to fit the 915 box, or any Porsche box for that matter, in to your VW, but for the purposes of this article we need not go into that. I will write an article on 915 into Type 3 installation in due course (probably after I have completely finished mine).

When I bought the 915 gearbox that I am using in the Ghia, it was a bit of an unknown entity, all that was stated when I bought it was that it was believed that 1st and 2nd synchros needed replacing, so along with the box, I was supplied with all the necessary parts needed to rebuild it.

I was originally going to pay a specialist to do this work for me but figured that I could save a LOT of cash by doing it myself. With the Ghia nearing completion I decided to take the plunge and dive in and have a go myself.

If you have a basic knowledge of mechanics / engineering this should be a fairly easy job to carry out. You will need some 'non - standard' tools to be able to achieve the job (namely a 36mm socket and a very large pair of water pump pliers or something similar) and also the permission of the wife / girlfriend to use the freezer for non food stuffs.

This procedure may differ depending on what you need to fix in your gearbox, for me all I needed to strip down was the 1st / 2nd gear layshaft, I'm sure that the 3rd / 4th gear layshaft is more or less the same.

First Things First

The first thing you will need to do is to drain the oil from the gearbox - this may be easier to do with the gearbox in the car. The oil can be drained though either of the drain plugs on the underneath of the gearbox - one under the diff housing and one under the geabox itself.

With the oil drained, you will want to remove the differential. I would advise to do this for a few reasons - the gearbox will be easier to move about, you can inspect it for wear, you can clean out the case and you can replace the oil seals. To remove the differential simply undo the nuts on holding the side cover in place. With the nuts removed, gently pull the drive shaft stub axle out of the case - it is simply pushed into the differential - the inner end of the shaft is splined and locates in a splined socket in the diff. With the drive shaft removed you can now remove the cover to expose the differential. To completely remove the differential you will need to remove the opposite drive shaft stub axle - this is held in place by exatly the same manner.

With the differential removed, turn the gearbox so that it is resting on the bellhousing with the selector shaft in the air. Now it is time to remove the nose cone. simply undo the nuts holding the nose cone in place. with the nuts removed the nose cone should simply slide off of the selector shaft. be careful of the point on the selector shaft where it bolts to the shaft in the car as the shaft may be burred. If this is the case remove the burrs with a file before hand.

With the nose cone removed you can now see the 5th and reverse gears, along with the 5th gear synchro, as well as the selector mechanism. The 5th gear selector mechanism is the brass horseshoe shaped fork and shaft. The 5th gear selector mechanism will simply pull out of the case whilst sliding the synchro mechanism upwards - the detent ball that allows the selector to click into position should be retained within the case, however, this may not be the case if it is worn so be ready for a ball bearing flying out.

The rest of the gears and bearings can be slid off of the shaft - be sure to make a note of the order and oorientation of the parts you remove.

To strip down the gearbox any further you will need to remove the 36mm nut on the end of the 1st / 2nd gear layshaft. First you will need to remove the 'dimpled' part of the nut that retains it in position by gently piening it out with a hammer and cold chisel. The nut is not very easy to remove as the shaft spins and is difficult to hold. I removed mine by using a large pair of water pump pliers to hold the shaft. I placed the gearbox on the floor and locked the pliers up by rotating the shaft until it was pushing the pliers against the floor whilst applying pressure with the socket and knuckle bar (and my foot). This may be much easier as a 2 man job. I actually had to stand on the knuckle bar to get the nut undone. Dont worry about damaging the shaft - it is hardened and likely a lot harder than the pliers so will not scratch.

If you have access to the correct tool to hold the shaft, this is obviously better. Alternatively it is very easy to make one, but you will need to have a spare scrap 915 gearbox. To make the tool simply weld a bar onto the synchro housing that slides up and down on the shaft so that you can use it as a giant spanner.

With the nut removed the next step is to remove the cover on the side of the gearbox, this allows the selector shaft to be rotated out of position. You can now undo the fixings holding the housing in position and slide the housing up. The selector shaft will need to be slid along with the housing, you can remove the selector shaft from the housing after the housing has been removed.

With the gearbox casing removed you can now inspect the gearbox for wear / tear and damage. With my gearbox it was very obvious where the damage was as there were no teeth left on the dog gears for first and second gears and the synchro ring for first gear was bent and hanging out of the side of the synchro assembly.

The Gears can now simply be slid off of the shaft, they may be a relatively tight fit, and need to be gently prised off but should not need excessive force to remove. Again, make sure that you take note of the order and orientation of each component.

One thing worth noting is that 1st gear and 2nd gear dog gears are a different profile, the synchro gear is also a different profile to match - These must be replaced correctly or you will find it difficult to select gears. The first gear profile is not symmetrical whilst all of the other gears are.

If like me, you have worn synchros / dog gears, you will need to strip the synchros down. The synchro rings are held in place by the giant circlip on the end, this can easily be removed with the use of a decent set of circlip pliers. Be careful when removing this as it may 'ping off' across your workshop (and as usual when carrying out this type of job make sure you are wearing appropriate eye protection).

With the circlip removed the synchro ring, inner ring and locator can now be removed, make a note of which way round the synchro ring fits as it may not be symmetrical. The next task is to remove the dog gear. This can be acheived by placing the gear and a vice a using a very sharp cold chisel drift off the dog gear. If this does not work for you - you might want to try grinding the dog gear off with a dremel (very small die grinder) - this was the method reccomended to me by the shop that sold me the gearbox.

With the Synchro disassembed the next stage is reassembly.

Please note that I am only describing the procedure for first and second gears, I did not need to strip down 3rd / 4th gears but the procedure should be the same.

Before I embarked on the rebuild, the part that I considered to be the hardest was rebuilding the synchros, I have never rebuilt a gearbox before and only had heard horror stories about how hard it was and how you needed a 100, 000 ton press, and how huge gears would spring around the workshop on dissasembly. After doing it, I felt that it was relatively straight forward. Maybe I was lucky??

The main thing to remember when assembling the synchros is that the dog gear is an inteference fit onto the main gear. In essence the dog gear is smaller than the gear it fits onto. if you try to do this by hand you will normally not be able to fit it, the best way to do it is as follows.

Leave the main gear in the freezer, this will in effect shrink the gear. I left mine in there for about three or four hours. when you are ready to assemble it you will need to heat up the dog gear, this has the effect of making the dog gear expand, you can do this a number of ways - probably in the oven is best. With the main gear shrunk and the dog gear expanded you should now be able to carefully drift / press the gear into position. I drited my gear into position as I do not have a press in my workshop, this was easy enough but does involve a little skill to do properly. I will not go into how to do this here as I am assuming that by undertaking this rebuld you already have some basic engineering / mechanics knowledge.

With the dog gears fitted the rest of the synchro can now be reassembled - reassembly is simply the reverse of taking it apart.

Reassembly of the rest of the gearbox is also the reverse procedure of taking it apart. obviously new seals and gaskets need to be fitted, along with new oil seals where necessary. A gasket kit contains all seals, gaskets and o-rings needed.