Good Afternoon Folks,
Here is some useful information for anyone suffering from badly corroded rear beam axles. Apologies in advance; I didn't think to take many photos while undertaking this project.
I recently acquired a 2002 1.4tdi, from a pal of mine, who was going to scrap it. On the surface it looked to be in pretty good condition (don't they all!), but once I got it home and gave it a good looking over, it became obvious that most of the steel suspension components should not have passed the last MOT. Of particular concern, the mounting points for the rear shock absorbers, on the beam axle, had the structural integrity of wet cardboard.
Up to this point the car had cost me basically nothing, so I took the decision to throw a little bit of money at a suspension refresh. Most parts were pretty easy to source through ebay, Euro Car Parts etc, but the rear axle (being beyond saving), was a different matter. I found a couple of used examples on ebay, but these were located in Europe, with a hefty shipping bill and no guarantees that they were any better than the one I already had. I also took a look at a couple of examples that were being broken locally and both of those were equal to, if not worse than, the one I started with. Of course, I could have left it up on axe stands for a few months to wait and see if a good used example would come available, but I decided to look for a better fix.
I had read a couple of threads on this forum, where people were discussing a Mk 4 Polo axle as a possible replacement. However, so far as I could tell, nobody actually seemed to have attempted it. With no better options available to me at the time, I decided to take a chance on a Polo axle, which I found in mint condition on ebay. Including shipping, it was a £140.00 gamble.
Now at this point I should probably disclose that I am not your regular hobbyist mechanic. I'm actually an experienced mechanical engineer, with a background in aerospace engineering, so I did have the skills and knowledge to make informed decisions at all stages so of this project. Once the new axle arrived, I set about measuring every conceivable dimension and angle and then comparing it to the original (where enough of the original survived to be measured). The results were certainly interesting. To all intents and purposes, the vast majority of dimensions / angles were basically identical (plus or minus the thickness a coat of paint). I did however identify three key differences between the two axles:
1) The bracketry and mounting points for the brake pipes / hoses is (understandably) quite different. Of specific note, the A2's brake hoses are both routed along the L/H side of the car, joining the beam axle together, through the same bracket. On the polo, the brake hoses join separately, one on the left and one on the right. It was not particularly complicated to grind off the un-wanted Polo fittings and tack on some suitable replacements, replicating the mounting points from the A2 axle (sorry, no pictures). Note: These axles are oil filled (to prevent internal corrosion) and made from surprisingly thin steel (especially along the concave rear face). Great care should be taken when welding anything onto these, so if you're not a great welder, I strongly recommend you pay someone competent to do it for you.
2) The spring seat on the A2 features an additional tubular projection, which helps to locate and retail the base of the spring. I did seriously consider leaving this as it was (its ok on the Polo, right?), but I figured that Audi must have made this change for a legitimate reason. I ordered a length of mild steel tube from ebay (47.6mm OD, 3mm wall), which was an absolutely perfect fit for the hole in base of the spring seat, and simply welded it on, around the base. (see picture).
3) It seems to be well known what the A2 and the Polo use quite different forward bushes on the beam axle. These bushes are also fitted the opposite way around (i.e inboard to outboard on the A2 and outboard to inboard on the Polo). What isn't widely discussed is the fact that the aperture for the forward bushes is approximately 5mm narrower on the Polo, vs the A2 (difficult to be super accurate due to the corrosion on the A2). I honestly thought this was going to be a show-stopper, as the placement of these bushes would affect the geometry; Even I wasn't confident about the idea of cutting and re-welding these items. However, luck really did turn out to be on my side with this one. I had already struggled to track down any genuine A2 bushes (they seem to be getting quite scarce too), but had instead ordered a set of Powerflex PFR85-610 polly bushes. Although these items are listed as compatible with both the A2 and Polo, this kit is clearly intended primarily for use on the Polo. When they came, the Poweflex bushes featured a deeper shoulder (5mm deeper), which, when orientated inboard to outboard, exactly compensated for the narrower housing and placed everything exactly where it needed to be. In fact, everything lined up so perfectly, I struggle to believe that these bushes would actually fit a standard A2 axle without modification (do people usually cut some material off the shoulder of the bush or something?)
With these modifications made, the axle went straight back on, with all of the holes lined up nicely etc. The following week we took it in for a laser wheel alignment and an MOT, both of which it sailed through, without any problems. I have to say the car seems to handle very well and so far, (600 miles later) it does not appear to have suffered any ill effects from my gene-splicing experiment.
So, can you fit an Mk 4 Polo axle to an A2? - Yes, you 100% can!
Is it easy? - Yes and No. You're not going to be able to throw it straight on like an original part. It is going to require a little bit of modification including some welding and fabrication of brackets etc. However, when you think of the effort involved in removing the rust from an original, then treating and re-paint it, I don't believe it is a bad investment in effort. Of course, I've now got a (basically) brand new rear axle, which should last at least another 20 years.
Here is some useful information for anyone suffering from badly corroded rear beam axles. Apologies in advance; I didn't think to take many photos while undertaking this project.
I recently acquired a 2002 1.4tdi, from a pal of mine, who was going to scrap it. On the surface it looked to be in pretty good condition (don't they all!), but once I got it home and gave it a good looking over, it became obvious that most of the steel suspension components should not have passed the last MOT. Of particular concern, the mounting points for the rear shock absorbers, on the beam axle, had the structural integrity of wet cardboard.
Up to this point the car had cost me basically nothing, so I took the decision to throw a little bit of money at a suspension refresh. Most parts were pretty easy to source through ebay, Euro Car Parts etc, but the rear axle (being beyond saving), was a different matter. I found a couple of used examples on ebay, but these were located in Europe, with a hefty shipping bill and no guarantees that they were any better than the one I already had. I also took a look at a couple of examples that were being broken locally and both of those were equal to, if not worse than, the one I started with. Of course, I could have left it up on axe stands for a few months to wait and see if a good used example would come available, but I decided to look for a better fix.
I had read a couple of threads on this forum, where people were discussing a Mk 4 Polo axle as a possible replacement. However, so far as I could tell, nobody actually seemed to have attempted it. With no better options available to me at the time, I decided to take a chance on a Polo axle, which I found in mint condition on ebay. Including shipping, it was a £140.00 gamble.
Now at this point I should probably disclose that I am not your regular hobbyist mechanic. I'm actually an experienced mechanical engineer, with a background in aerospace engineering, so I did have the skills and knowledge to make informed decisions at all stages so of this project. Once the new axle arrived, I set about measuring every conceivable dimension and angle and then comparing it to the original (where enough of the original survived to be measured). The results were certainly interesting. To all intents and purposes, the vast majority of dimensions / angles were basically identical (plus or minus the thickness a coat of paint). I did however identify three key differences between the two axles:
1) The bracketry and mounting points for the brake pipes / hoses is (understandably) quite different. Of specific note, the A2's brake hoses are both routed along the L/H side of the car, joining the beam axle together, through the same bracket. On the polo, the brake hoses join separately, one on the left and one on the right. It was not particularly complicated to grind off the un-wanted Polo fittings and tack on some suitable replacements, replicating the mounting points from the A2 axle (sorry, no pictures). Note: These axles are oil filled (to prevent internal corrosion) and made from surprisingly thin steel (especially along the concave rear face). Great care should be taken when welding anything onto these, so if you're not a great welder, I strongly recommend you pay someone competent to do it for you.
2) The spring seat on the A2 features an additional tubular projection, which helps to locate and retail the base of the spring. I did seriously consider leaving this as it was (its ok on the Polo, right?), but I figured that Audi must have made this change for a legitimate reason. I ordered a length of mild steel tube from ebay (47.6mm OD, 3mm wall), which was an absolutely perfect fit for the hole in base of the spring seat, and simply welded it on, around the base. (see picture).
3) It seems to be well known what the A2 and the Polo use quite different forward bushes on the beam axle. These bushes are also fitted the opposite way around (i.e inboard to outboard on the A2 and outboard to inboard on the Polo). What isn't widely discussed is the fact that the aperture for the forward bushes is approximately 5mm narrower on the Polo, vs the A2 (difficult to be super accurate due to the corrosion on the A2). I honestly thought this was going to be a show-stopper, as the placement of these bushes would affect the geometry; Even I wasn't confident about the idea of cutting and re-welding these items. However, luck really did turn out to be on my side with this one. I had already struggled to track down any genuine A2 bushes (they seem to be getting quite scarce too), but had instead ordered a set of Powerflex PFR85-610 polly bushes. Although these items are listed as compatible with both the A2 and Polo, this kit is clearly intended primarily for use on the Polo. When they came, the Poweflex bushes featured a deeper shoulder (5mm deeper), which, when orientated inboard to outboard, exactly compensated for the narrower housing and placed everything exactly where it needed to be. In fact, everything lined up so perfectly, I struggle to believe that these bushes would actually fit a standard A2 axle without modification (do people usually cut some material off the shoulder of the bush or something?)
With these modifications made, the axle went straight back on, with all of the holes lined up nicely etc. The following week we took it in for a laser wheel alignment and an MOT, both of which it sailed through, without any problems. I have to say the car seems to handle very well and so far, (600 miles later) it does not appear to have suffered any ill effects from my gene-splicing experiment.
So, can you fit an Mk 4 Polo axle to an A2? - Yes, you 100% can!
Is it easy? - Yes and No. You're not going to be able to throw it straight on like an original part. It is going to require a little bit of modification including some welding and fabrication of brackets etc. However, when you think of the effort involved in removing the rust from an original, then treating and re-paint it, I don't believe it is a bad investment in effort. Of course, I've now got a (basically) brand new rear axle, which should last at least another 20 years.
