Hop Skip and Jump

( THE THIRD IN AN OCCASIONAL SERIES PROVIDING HELPFUL HINTS ON HOW TO KEEP YOUR MERLIN IN TIP TOP CONDITION.) Inspection of the trailing arm bushes on the rear axle will undoubtedly form part of everyone's routine maintenance programme. The !**? it will. I hadn't given it a thought in the 10 years my car has been on the road. Lets face it they are not by any description easy to inspect being almost entirely surrounded, the only visible one being where the panhard link to the axle. The methods to spot wear are therefore the disconnection of the trailing arms or observation of other symptoms which may manifest themselves. It was the later route which lead me to look a little closer.

Routine service was undertaken during the winter with nothing obviously amiss. This was followed by the MOT ( or whatever it's called now). Again passed without problem. My suspicion was aroused when as a result of changing the wheels about I noticed that the suspension brackets on the axle appeared somewhat less than perpendicular, in fact on the passenger side so far out of line that the shock absorber was rubbing the inside of the spring.. I remember a number of members having problems in the gear box, prop shaft and diff as a result of the brackets having not been welded exactly in line and as a result started to suffer one of my many repeat bouts of anxiety. The welds were all intact and the brackets hadn't moved, There was no evidence of problems on the chassis mounts and at first ( very restricted viewing) no apparent problems with the bushes Think again.

Since the bushes are virtually impossible to see it is very hard to determine wear and whilst a relatively easy task to systematically undo and remove each arm, it was not a route I wished to pursue unless no other alternative could be found.

Bushes will deteriorate in one of two ways. Either general break down of the condition of the rubber or a tendency for the central sleeve to be gradually pulled off centre. The former is almost impossible to detect without removing the arms the results of the latter can be observed if you manoeuvre yourself to a point either immediately above, ( not much room for this approach) , or immediately below the bushes. From this perspective it is quite easy to see if the mounting bolt is passing through the centre or if there has been movement. An odd millimetre or so may not be noticed, a full 5 mm of centre does tend to stand out.

Old Bush

What had actually happened was that not only had the centre been pulled to one side, in the example above by some 5 to 6 mm but also the rubber was breaking down quite considerably leading to the edge pulling away from the sleeve. Multiply the likely effect of this 8 times and I started to understand some of the strange sounds and less than perfect ride that the back end had been giving for some time.

The solution is relatively simple and not overly expensive, just replace the bushes. The first problem to be over come is merely one of supply. The actual bushes used are from the lower rear trailing arm of a Mk 3 Cortina. For some unexplainable reason, maybe that the Mk 3 stopped production 20 years ago ( give or take a few years) Ford no longer stock them. They are however available from either Quinten Hazel Autogem ( see end for technical bits ).

Fortunately my supplier ( one of my customers ) just happened to have no fewer than 20 in stock ( I've been trying to get him to do something about his poor stock control and feel I have just shot my self in the foot in this respect). He did however tell me that the number of manufacturers now listing this part is now down to 2 or 3 where as only a year or so ago it was 4 or 5. May be worth laying in a small stock. Cost around £5 each or less.

As you will all no doubt be aware replacement of a bush is a relatively easy operation requiring only a method of applying a few 100 Ibs of pulling force in an exact parallel to the bush sleeve. This requires a special tool which can be purchased relatively cheaply but is of course cheaper still if you happen to know someone who has got one ( Thanks Gary, I'll get it back to you soon). The only difficult area is getting the tool correctly aligned. Given the degree to which my bushes were off centre this necessitated drilling a series of holes into the rubber of the bush to allow the inner sleeve to move back to ifs central position. When centred correctly a force of about 50 ft Ibs or less applied to the bolt of the tool is sufficient to pull the old bush out, with a similar force needed to insert the new.

Alignment is a little hit and miss with the smallest fraction off centre making it impossible to move the bush. ( I managed to snap one bolt and strip the thread of another two. We are talking 12mm high tensile bolts here so you can imagine the force needed to do that).

I changed the bushes one arm at a time having jacked up the car and supported the rear end with blocks under the chassis, at the same time supporting the weight of the axle with a jack under the diff. This allows the arms to be removed and reinserted quite easily. It is best if all the mounting bolts are slackened off together and certainly they should only be tighten up again when all the arms are back in place and with the full weight of the car on the axle.

New Bush

All in all I found the task considerably less traumatic than I had imagined, took little more than a full day and has left me with an excellent performing rear end!!!!! ( I also replaced the bushes on the panhard rod although in reality they didn't look too bad.

Technical Bits

Original Part -
Cortina MK3 Rear suspension bottom arm front bush
FORD PART Number 1481426 ( unlikely to be available )

Alternative Manufacturers -
Bush outside diameter 43.4mm

Handy Hint Try freezing the bushes overnight the slight contraction in the diameter seemed to make a lot of difference. ( psychological perhaps ??)

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