Although the article of "How To" has already been done in a well known magazine, there were several rather important issues I felt which were not addressed which would definitely make them selves apparent when you got to the installation yourself. The first being that the earlier 901 gearbox comes with a push type clutch, not a pull type as previously stated. The later 911 gearbox comes with the pull type clutch and then around 1972-73 ish the 915 came along. I won't be including the 915-gearbox installation in this article for the prime reason that I haven't done it myself. I only believe in writing about things that you have actually done yourself. Oh, before you go any further the fitting of a Porsche 901/911 box will only work with an IRS chassis. Anyway, here goes.

The 901/911 Gearbox.

The 901 gearbox was used from the first 911 in 1965 until some time in 1968-69. Then the 911 box took over. The 915 gearbox replaced the 911 box in 1972-73. The basic difference between the 901 and the 911 gearboxes is size. The 911 is bigger. It uses very few identical parts so it is stronger. The 901 should be good for around 150hp where as the 911 should take 200hp. These are advisory figures, if you start drag starting a 911 box at every opertunity it's not going to last as long, just like a beetle box. The 901 box uses a push type clutch action where as the 911 uses a pull type clutch action which needs to be modified for our application. Both have a dogleg first gear and have reverse placed directly in front of it. If you don't like the idea of this, then go for a 915 gearbox as this will bolt in the place as a 901/911 but beware, the prices are somewhat more expensive.

Which Box?

First decide which box you are going to buy and check out the numbers on the bottom and compare them to a Porsche chart to be sure that the ratios are really what you are after. Then try and find something out about the box, history, any known problems or difficulties that have arisen in the past with your box. If there is no history then I would suggest you try to get the seller to allow you to pull the cluster before purchase. That way you can be sure of what you are buying and what you are going to have to replace. Always look at having to buy atleast a gasket set before anything else.

Mounting your Porsche Box onto your Beetle Chassis.

If you have a 911 box you will have to cut off a small piece of the case which is where the rear gearbox mounts would normally be on a T1 gearbox. Then you have to mark out and drill the four holes necessary for the stock Beetle rear gearbox mounts. On your chassis, you must remove the front gearbox mount bracket (pre-72 beetles). You must also cut a hole in the bottom of the tunnel for the hockey stick (gear selector rod) to go through. How you do this is entirely up to you but a snug fit to the gearbox with some kind of box to meet the box will keep out the elements more than just cutting a hole in the tunnel! I have used the stock 911 front crossmember for the gearbox front mount. It needs some modifying to make it fit but atleast you can fit replacement 911 gearbox mounts to it when they wear out. You will need to weld on some brackets to the bottom of you IRS a-arm bracket for the front gearbox cross member to bolt to. You will have to clearance the N/S (left looking from the back of the car) chassis fork to let the clutch arm have enough room to work. Once all this is done you should have a firmly mounted gearbox in your chassis.

Getting all FIVE gears!

The gear selector shaft, which runs from the hockey stick to the gear lever, needs some careful adjustments to make it line up with the new gearbox. I have seen everyone else fit the gearbox and fit the gear lever and massive chunk from the floor of a 911 when this has been attempted in the past but I managed to get the stock Beetle items to work. You have to shorten the shaft and then bend it twice so that the bar starts to look like a letter Z. It doesn't take much and then it should line up beautifully with the 901/911 hockey stick. You will have to drill a new hole in the hockey stick for the securing bolt to go into from the Beetle coupler. Now you will have to take the gear lever reverse lockout plate and cut the section out which stops you from being able to go directly forwards from reverse in a stock Beetle. This should now give the gate enough room to incorporate the extra gear. I use a Scat Dragfast so this was not necessary on my Beetle. I just pull up the lever and pull back for first while reverse is directly in front of it. Just be careful going from 1st to 2nd. It takes practice, as any early 911, 914 or 924 GT owner will tell you.

Clutch action - Push or Pull?

If you have gone for a 901 box then things are a bit simpler than if you have gone for a 911 box. The difference mentioned earlier about the clutch action will have to be addressed on the 911 box. You will have to replace the clutch arm and related parts with parts from a 901 box. This is the only way to have a clutch action that is compatible with a Beetle or T4 engine. The process involves drilling and tapping a hole in close proximity to that of the original for the clutch arm pivot ball, (Obviously easier to see when you have a box!) so with having to do this you are going to have to have the box in pieces to clear out the swarf. Then bolt up all the related parts from the 901 including the release bearing.

Flywheel Depths and related problems.

This is one of those very important things that were not mentioned. If you were to bolt your Beetle or T4 engine with it's stock flywheel up to your 901/911 gearbox, you'd soon realise that there's a problem with the starter. It doesn't engage! Or if it does, it won't for much longer! When the T4 engine and the 5 speed Porsche gearbox were used in the 914, a deeper flywheel was necessary to reach the starter. We are only talking about 7-8mm but just imagine how much power is going through that starter to turn your engine. If you plan on using a Beetle engine then the answer is to use a 912 flywheel. If you plan on using a T4 engine, then you need a 914 flywheel. You will need a Porsche starter motor for both of these applications.

Clutch Release Bearings.

I have used a Porsche release bearing on my box but it looks as though it may be able to fit the Beetle item saving a lot of money. As I haven't done it, I'm not gonna' talk about it.

Clutch Cable.

You can use the stock Beetle cable for this installation. You need to buy the proper fittings for the end of the cable, which match the clutch arm from Porsche but that's all. Take a Beetle clutch cable holder from a late beetle box (it bolts onto the side plate) and cut it in two. (This is not easy to describe and as mine is on my car it's not easy to photograph either). What you are trying to do is create the mirror image of the Beetle item. Once in 2 pieces you should be able to slide it onto the Beetle clutch cable and bolt it onto one sideplate bolt of your 901/911 box. Now straighten out the other piece and bolt it onto the next bolt on the sideplate and tack weld the 2 together. Then take off your new bit and finish the welding. You will have to cut off some of the original clutch cable holder from the 901/911 sideplate but be careful, the casting comes some way out inside it so if you go too far, you'll end up with a hole. Just cut enough off to clear the chassis fork next to it.

Output Shafts and Driveshafts.

If you have a 911 gearbox, then the output shafts will look huge in comparison to the Beetle CV's. You need 901 output shafts. These are the same size as Beetle CV's but use four bolt and 2 dowels. Drill the 2 holes that match up to these dowels to the bigger size of the dowels. You can then use stock Beetle driveshafts. Tip - If you are transforming a swing axle chassis to an IRS chassis, you will have to do some pretty heavy work to the tops of the chassis forks with a big hammer just where the output shafts and CV's fit. The IRS chassis already comes with this area clearanced. If you are planning on using more than 120hp with either of these gearboxes, then look at using the 911 output shafts with 930CV joints, (stock 911 size) 911 driveshafts and 944 hub shafts. You will have to have the 911 driveshafts machined to take the 944/T2 CV joints on the outer end but this should be strong enough for 200hp.

Thanx to Performance Ghia.