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Although the axle sticking out of rear swing arm might look as though it is not replacable; it is and often should be! While the swing arm will bend more often than the axle, it does happen. And if you spin your bearing on the axle it will also wear a grove that replacement is the only answer. AND if you are converting from wet to dry suspension then axle replacment could be an easy solution to the lower mounting of the rear shocks!
Note that the threads are different for each side of the car - use the axle with the standard threads on the right side of the car, and the axle with the "backwards" threads (turn left to tighten) on the left side of the car.
SUSPENSION - Converting from wet to dry
The steady decline over the past several years of readily available hydrolastic displacer units has prompted an escalation in the number of folk asking how to go about swopping from hydrolastic (‘wet’) suspension systems to the far more wide spread ‘dry’ set-up. As in all things, with enough skill, enterprise, facilities, and money - anything is possible. Being all too ready to oblige in anyway I can, here’s the relevant details of the most practical way of going about it for the majority. It's not the 'be-all-and-end-all' definitive article on all the possible permutations, just the simplest way out. And it’s nowhere near as difficult as most folk seem to think it is.
Paddling about in the past
Unfortunately the pitching problem worsened, particularly under severe use of the go/stop pedals. Fully laden, rear end sag caused complaints by low flying aircraft - German authorities taking the severest line by banning hydro cars from sale in Germany. Further development/refinement was needed, but the hierarchy cried ‘enough’, and withdrew fitment in 1969 - although it stayed fitted to the S right up until it’s demise in 1971. In fact a few early GTs were hydro equipped too. The BMC big-wigs decided the extra expense of manufacturing the complex displacer units, and further development funds needed just weren’t justified for the perceived little extra gained. Shame, because many years further on, some individual development has seen superior results over the dry set up. So much so that there’s discussions about making new displacer units using modern technology!
Starting at the sharp end, whichever way you go engine removal will make things a whole lot easier. I know some folk advocate removing the entire engine/subframe/suspension assembly in one go by lifting the body over the top of it all - having disconnected everything first, naturally. I did this once, never again. You need an army of companions to man handle everything about. A right pain.
Now, it’s entirely possible to modify the hydro front subframe to accept the rubber springs and other necessary bits and pieces. The displacer unit is seated in the tower in the same way as the cone, the difference being the locating ring's size/shape. The displacer sits inside it’s seating ring, the cone outside. The diameters of these differ too, the hydro being bigger, and has lugs pressed into it. To get the rubber spring to fit the hydro ‘frame, these lugs need to be bent outwards. The rubber spring then locates inside the ring. Sounds easy, eh? Achieving this is accompanied by all kinds of 'blue' air and skinned knuckles. More often than not, eventual submission and fitment of a dry ‘frame!! It’s all down to access - or lack of it (as in ‘severe’). There are ways round it, but we’re supposed to be doing this the easy way, remember? Then you need to drill holes in the tower outer ‘elbows’ to take bump stops. Use the later single stud fixing as this eases the whole drilling/fitting thing.
So it’s a dry subframe then. The easiest is to use the pre 1976, non-rubber mounted type, as this bolts straight in using the fixings from the donor car except it uses bolts in the towers rather than the studs of the hydro one. Floor pan and front panel mounting holes are all in the same places. Using the later rubber mounted one has complications. Leyland decided to rubber-mount the front subframes in an effort to make the aged Mini more civilised. Consequently they isolated the front ‘frame from the shell using rubber mounts between the front, rear, and tower mounting points. These make it easily identifiable, along with the humungous, 1-5/16”AF-headed bolts used to fix the ‘frame to the shell through the bulk head into the towers. You’d need all these from the donor car - unfortunately ninety nine times out of a hundred they’ll all be shot so new ones would have to be bought - more expense! You need them bolts too - they’re real expensive new!! Make sure you get the metal washers under the bolt heads also. Although the lower front and rear mounting point holes are the same, the tower mounts present the biggest problem.
The post 1976 shells have a stiffening tube welded into the bulkhead to prevent it from being deformed/crushed by the bolt. This doesn’t happen when doing the big bolt up. When using the standard rubber tower/bolt mounts, the design has the bolt bottoming out on its thread to ensure ‘space’ for the rubber mounts to work in. The deformation occurs in use, as the support tubes for the original twin bolt/stud fittings aren’t in the right places to be effective. Using solid mounts actually slightly improves things a bit - although causing slight deformation when doing the bolts up, the reduction in movement in operation reduces further deformation markedly. See separate article for bush and mounting options.
When removing the ‘frame assembly from the donor, make sure you unbolt and keep the top damper mounting brackets. They’re held to the body by four 7/16”-AF bolts wound into captive threads. These captive threads are on every shell, including the hydro cars - you may have to dig through the cack and poop to find them though!
Bringing up the rear
I’ve never taken a rear ‘frame out of a car and found it useable, so I don’t see why any of you should be any different! Useable, ‘as new’ condition, second-hand ones are rare. Considering the relatively low cost against the severe aggro of fitting a rear ‘frame - buy a new one. Treat it with some decent rust proofing gear, and have no worries. The fitting holes in the shell are all the same, so even the later post 1976 mounts will fit OK. Just remember when buying service parts (i.e. rubber mounts) which ones you’ve used.
Now the back end. As with the front you’ll need rubber springs, ally trumpets, dampers, suggest new knuckles for what they cost, new radius arm to wheel cylinder brake pipes (hydro’s are shorter as they fit under the arm instead of on top), and last but not least - hand brake cables. Two of each once more. Now, to avoid all sorts of hassle, it really is strongly advisable to use dry-type radius arms. The hydro design will see your Min fall flat on it’s arse unless you get some severely lengthened rear trumpets. Then there’s nowhere to bolt the dampers to. The dry type have a pin sticking out to take them, the hydro doesn’t. This damper mounting pin is part of the rear stub axle, swopping these can be an absolute nightmare and they’re not cheap either. It’s cheaper in the long run to buy a pair of completely refurbished dry arms. Honestly.
Other useful stuff.
At the front, replace bottom arm bushes (slight snag, keep reading), tie-rod bushes, and check the top-arm shafts and bearings. These consist of two caged needle roller bearings, one pressed into each end of the top arm. They’re subject to seizure/wear as most folk completely neglect greasing them. Rebuild kits are reasonably priced. Once done, don’t forget to grease them regularly in future!! Bottom arm bush snag thingy - before buying parts for them, you need to check which type they are, The early arms used a top hat type bush, later ones a tapered, metal-sleeved type. To identify, peer into the holes in the bottom arm. If the walls are tapered, use the later style bush. Parallel sides indicate the earlier type. Unfortunately you can only get up-rated bushes for the later tapered type. Using up-rated bushes improves stability - particularly the tie-rod ones. These reduce weaving under braking, and fractionally help to reduce roll (long story!). For material options, see separate article.
The radius arms at the rear are the biggest problem. If you use recon ones, no worries, but if you use the existing ones, overhaul the pins and bushes. Inexpensive to buy but a bit of a pain to fit since the outer bronze bush needs reaming after fitment. Most engineering companies can do this, but again - recon arms are really cheap when bought on exchange. Otherwise it’s just the ‘frame mounting rubbers that need attention.
Lastly, the only specialist tool you’ll need to do the job is the rubber spring compressor. Cheap enough to warrant the investment as you’ll need it again in the future.
Useful part numbers: