You just undo a few bolts, someone told me…
I wish it was that straightforward to drop the rear axle on the 924 S. Alas, being a transaxle it wasn’t quite that simple. Why would one want to drop the axle? To fit my shiny refurbed petrol tank, naturally. So, simple job then; drop the rear axle, remove the old tank, install shiny tank and then replace the axle.
Couple the fact that this was the biggest job I’ve undertaken with a 26 year old car and you’ve got something that was never going to go smoothly.
I’d felt a little nervous about the idea of jacking the car in the air and then getting under it, so I supplemented my jack and stands with some borrowed from a friend, Joel. Paranoia rules in my garage, and I suspect I am all the safer for it!
With the car is the air, I deftly slid myself under to remove the exhaust. In true #Project924 style I soon had an eyeful of rust as I attempted to loose the first nut; disconnecting the rear section of the exhaust from the front. After a little swearing and a bathed eye, I donned my goggles and went back in! The five minute process took close to an hour and set the scene for the task in hand. Thankfully the rusted heat shield came off easily, although had clearly seen better days! Next I disconnect the gear selector (on top of the gearbox) and went into the cabin to disconnect the selector rod from the gearshift. This process went surprisingly easily. Then it was back to the gearbox to push the selector rod clear of the bellhousing. At this stage I was beginning to feel like momentum had swung back in my favour. Fool.
The next task was to de-couple the torque tube from the transmission. I removed the rubber covers from the bellhousing easily enough and then battled trying to turn the coupler so that the first bolt was infront of me. The task became demonstrably easier once I depressed the clutch. I live and learn. The bolts, two of them, in the coupler, take a hex head to undo. I tried with my socket set but the opening size and angle meant I could not get one seated squarely so I swapped over to my large hex key set. The problem here was that I needed to use the longer end to access the bolt which left me with the shorter end and little leverage to undo it. It wasn’t working. I tried attaching spanners and nothing was helping. After some time, I don’t know how long only that I was becoming frustrated, I decided it was better to walk away and regroup rather than rounding off the bolt and doing irreparable damage.
Closing the garage door I stopped off into town to look for inspiration in the hardware store; buy my way out of trouble. At some point I tweeted my discontent. I found nothing in the shops, but when I fired up my Twitter app again, I had a number of suggestions, now it’s been a while so I hope these are correctly credited:
The above list doesn’t include everything, but “go to the pub” wasn’t going to solve the bolt situation. So I drowned the bolts in WD40 and gave both a bit of a whack. I then went inside for a cup tea. I emerged half an hour later and set about making a tool with a little more leverage. Insert the required hex key into the end of a socket extension rod I use a smaller hex key to wedge it in tight, then applied a large amount of duct tape to hold everything fast. The resulting tool was nothing short of an engineering masterpiece:
I dried the bolts and coupling as best I could and turned a heat gun on the assembly. Before too long everything within five feet of the bolts was too hot to touch; there may be some exaggeration in that but my exuberance that afternoon did get everything very hot indeed. I applied the tool of destiny (I think that is a fitting name?) and the first bolt came loose! Clutch in and I now had a slight issue turning the coupling as it was so hot. Before too long the bolts were removed, I marked the position of the coupling and then slid it out of way. Narrowly avoiding burning my fingers.
I moved back to the transmission. Removing four bolts around the bellhousing it was the tranny was held in place only by the two transmission mounts. I was starting to get a little worried now. I knew the transmission would be heavy, I had even seen it described as the “heaviest thing I’ve ever lifted”. Given that the [home DIY] removal process involved balancing it on a jack and lowering it, I was a little worried I’d be crushed. A little melodramatic? Possibly, but I didn’t know what to expect.
I positioned a jack under the transmission with a plank of wood on the top, for balance. I undid the bolts tentatively; a turn each. In little time the bolts were both out and I was not crushed. Huzzah! I gently pulled on the transmission to free it from the bellhousing. No movement at all. I tried lowering the jack a little, still nothing. I went through various combinations of pushing and pulling, and raising and lowering the transmission but it still wasn’t going anywhere. In a moment of frustration I decided to use a little more force and gave it kick with my heel. Nothing.
As is usual in these circumstances, when I am completely stuck, I tweeted Jon at JMG (@JMG_Porsche) for advice. Jon suggested the plastic tubing that the shifter rod goes through as not being pushed back, going to check to had previously been damaged (split) and wasn’t sliding back as it should. In addition, the metals on the bellhousing and transmission had corroded slightly and bonded together. Enough to stop them coming apart at least.
The following morning I got an early start. Given that the plastic tube protecting the torque tube was damage I went at it with a screwdriver and in a short time it was providing little resistance. Over night I had hatched another plan, to make handling the weight of the transmission a little easier. Rather than lowering the transmission I decided it would be easier to raise the car.
I took the car off of the stands and position a tool box underneath the transmission with wood to support it. Using a jack on both sides, alternating between them, I raised the car up one notch on the axle stand at a time, moving the transmission back at each stopping point. This attempt everything came away perfectly and I was able to slide the toolbox out the back of the car – needed to aim for the exhaust cut out for clearance. Clear of the car I lifted the tranny off of the toolbox and placed it on a plank of wood; it wasn’t as heavy as I had been led to believe.
With the transmission out of the way it was not too much trouble to remove the fuel tank, finally. There are straps on either side of the tank which need removing. The pipes into the top of the tank need to come off and then it is free from restraints. The fuel tank sits on top of a cross member and needs to be carefully slid out on each side. It’s a pain of a job but just needs a little patience.
With the tank out of the car I could immediately see the problem, why the fuel smell and occasional leaks when brimming the tank; the hose on the top that ran to the expansion tank was frayed and had quite a sizeable hole in it. I was a little frustrated as this must have been obvious when fitting; despite my not noticing when I bought it. Otherwise the tank looked very solid.
Given I couldn’t just pop the replacement tank straight in – I needed to get a few parts in from JMG Porsche – I decided to get on and tidy up my rather sorry looking transmission.
I also couldn’t stop myself cleaning the underside of the car. Cleaning the tranny was a simple enough job, I just cleaned it off with wire brushes, of various sizes, and a spinning brush bit for my drill; I did need to dismantle and fix the smoking drill before I started. As with most other tasks this became and obsessive job.
With the parts ordered and transmission cleaned I thought it would be a good time to pop in some fresh transmission fluid. There are two hex-nuts on the side of the gearbox which need undoing, one to drain and one to fill. A good tip I found when looking for instructions was to undo the fill plug first… rather than remove the drain plug only to find the fill plug is seized leaving an oil-less gearbox. Luckily the job went without a hitch.
When I stripped a few parts off of the transmission I notice that the mounts were look a little worse for wear so decided it would be an opportune time to replace them; it actually isn’t a difficult job to do even if not removing the transmission. I gave these parts a quick clean off along with a light dusting with straight to rust paint and while I was at it did the exhaust heat shield as well.
Before I fitted the replacement tank I decided it would be a good idea to further try to protect the area where the tank straps sit as this is a common point for corrosion. I masked off a couple of lines alongside where the straps run and sprayed with a few layers of Plasti Dip Rubber Paint. It was very easy, my only lesson here was to remove the tape while the spray is still wet. I also gave the fuel pump a quick clean up and coating.
I am pleased to report that reassembley was comparatively easy. I cannot be sure whether it was the new mounts or the gear oil change, but the gearshift seems a lot smoother than before. More importantly though, I filler the tank with petrol and there was no smell! I know the job has been a success as when I stop at the pumps I can hear the air release from the newly pressurised tank. A painful job well done.
Source of my instructions (let’s face it, you’re not going to repeat the job using the above!)…
How to remove and replace a Porsche 944 fuel tank (Square Dash Model)