Polyurethane suspension bushes are readily available nowadays and are a useful replacement for the original rubber type that can, and do, deteriorate with age exacerbated by exposure to oil and grease (see photo 1).
I decided to fit polyurethane replacement bushes at the rear of my TD as the shackle bushes (and rubber spring pads) had not been replaced during my original rebuild back in 1992, and had obviously been installed long before then.
I obtained the rear poly bush kit that comprises of eight shackle bushes and four leaf spring pads. I did investigate replacing the leaf spring front “silentbloc” bush but as I discovered this front bush has a steel insert (AAA629) and is not readily available as a polyurethane replacement. I also learnt that this bush is very hard wearing and not usually in need of replacement, unless it is showing serious signs of wear. As the silentbloc bushes looked in an acceptably good condition I left them unchanged for the time being.
Before I go any further I should issue the necessary “health warning”; springs are a taught bundle of energy and must be treated with due respect.
With the new polyurethane components at hand it is time to start looking at the dismantling process necessary to remove the bushes from the spring rear hangers.
The first thing to note is that the TD rear wing trailing edge is in very close proximity to the spring hanger, and indeed makes it difficult to attach the necessary spanners etc. without damaging the wing paintwork. In order to reduce this threat, I removed the lower three wing fixing bolts, and with the lower wing now free, gently forced in some soft padding, between the wing and the body, to hold the wing well out of the way.
The rear of the car was jacked up and two axle stands were positioned, one on each side of the end rails of the main chassis members.
A hydraulic jack was now positioned under the differential, on a piece of wood, to be able to raise and lower the axle to take the pressure off the (unloaded) rear springs as necessary. Two “G” clamps were positioned on the leaf springs – one each side of the U bolt clamping plate – to keep the spring “together”. After setting up the chassis for spring removal I found it best to tackle one side at a time, this way you always have a reference of how things should look.
Dismantling and Re-assembly (see drawing)
With the rear of the car off the ground and the spring “hanging” unloaded, remove the four nuts (31) on the U bolts (28) and gently lift off these bolts.
The nuts hold the bottom bracket (32) that is attached to the shock absorber link locating plate (29) and above this plate is the lower spring locating rubber pad (30).
The bottom bracket is attached to the shock absorber link arm (12), and this needs to be unbolted so that the arm can be moved out of the way to give access to the plates. On re-assembly I also used new polyurethane pads (30) under the spring. Although the old pads did not appear to be badly worn replacement seemed a good idea as I had the new ones at hand and everything unbolted.
The rear shackle pins (40) can now be removed (2 per side) in order to replace the (8) bushes per side. When the nuts have been undone the hanger plates (44) can be removed giving access to the “old” rubber bushes. The old bushes are pushed out and the spring eye cleaned.
Getting the necessary “access” to remove old shackle pins and re-insert new ones is made difficult by the very close proximity of the bottom edge of the rear wing. However the earlier decision, to unbolt part of the rear wing from the body, makes the job possible.
I used new shackle pins (40) on re-assembly as the old pins showed signs of wear. Reassembly is not difficult but silicone grease can help ensure the new silicone bushes are snugly pressed into the chassis eyes and spring rear eyes.
The jack, under the axle, can be of help to locate the position of the spring and chassis eyes in relation to the plates.
Note: The weight of the car should be supported by two axle stands.
It is also necessary to keep the lower part of the rear wing right out of the way during the shackle pin re-fitting otherwise wing paint damage can occur.
When the plates have been aligned, and shackle pins fitted, through both the upper and lower bushes, the washers and nuts (42) can be added.
The photo shows the new polyurethane bushes pressed into the upper chassis bracket (left) and the spring eye (right).
During the process of re-fitting the U bolts (28) I happened to noticed that the underside of these U bolts showed considerable signs of wear where they come into contact with the axle casting. On further examination I noticed the U bolts had also caused some rubbing on the top of the axle casing. MG parts suppliers now offer a solution to limit this wear that was fitted to the MGA as standard. This solution is a wrap around metal plate (47) that fits under the U bolts (see photo 4)
With all the new parts fitted, and the nuts appropriately tightened up, the wheels are re-fitted so that the axle stands can be removed and the car allowed to settle down on its new bushes.
Photo 4 showing the wrap around metal plate which helps prevent axle tube/U-bolt wear.
The Editor can also supply new MADE IN ENGLAND shackle pins in EN19T for the TD/TF (and YA/YB/YT) rear (same pin fits the TC front) and black poly bushes, specially made exactly as the original rubber ones (I own the mould); also polyurethane rear spring pads (‘saddles’) and interleaf spring pads made from Nylatron.