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MG MGB Technical - Replacement rear suspension bushes

Quick bit of advice required - what's the easiest/fastest was of change rear suspension bushes on a rubber bumper GT. I want to dismantly as little as possible but at the same time don't want to make the job any harder than it needs to be.

Thanks.
JH

I would think that the front bush would be OK as it is quite tough. That being the case it is only the shackle bushes that will need to be replaced and they are very easy to change if you jack the car and then jack the hub to prevent the end of the axle from dropping. Make sure that the shackle goes rearwards when you let the car back down,
Iain MacKintosh

Iave read that the spring eye bush can be very difficult to get out, and the new ones hard to press in situ.
I would guess that this one is a bench vice and socket job. Spring comes off. Itself not to hard at all, but alot more time consuming than just swapping out the shackel bushes

The shackel bushes are dead easy as Iain says and these are the ones that wear and allow your rear axle to move side to side. Which is not so good.
Peter

It's a little more involved than just undoing the shackle bolts, which these posts seem to imply. The axle straps prevent the axle and hence springs coming down far enough to *easily* get the shackle pins in and out. If you disconnect the straps you can't lower the axle much more before the brake flex hose comes under tension which is not a good thing.

You really need to support the body very safely - usually immediately in front of the rear spring front eyes using the reinforcing plate. If you know your axle straps are sound you can just let the axle hang on them, but otherwise you should support the axle as well (and change the straps while you are under there). Then you need to support the springs with a trolley (for security and safety) jack while you undo the U-bolt nuts, which allows the spring to come away from the axle. But only so far as the damper will then stop it, if you have lever-arms the bottom plate with drop-link attached can be manoevered out from under the spring (still supported by the jack).

Then you can jack the spring down until it is hanging from the shackles, but is still supported by the jack, then you can undo the shackle nuts and remove the shackles and bushes.

Replacement is the reverse of removal, except I found recent-purchase new rubber bushes had much thicker flanges than before which prevented my fitting the nut until I had clamped the two halves of the shackle together. See http://www.mgb-stuff.org.uk/wn_suspensionframe.htm and click on 'Rear Spring Replacement'.

People talk about making sure the lower end of the shackles points backwards, but I've changed springs on both chrome bumper and rubber bumper cars and I've always found that the shackle automatically goes backwards as it should just by jacking the spring upwards to meet the axle, let alone once the spring is attached to the axle and you start to lower the car to the ground.

There is no special torque figure for the U-bolts, so I suppose it is standard for the thread i.e. 55 ft.lb. with oiled threads. It would be wise to recheck the tension on these (as well as the shackle bolts) after a hundred miles or so, especially if you replace the rubber pads 'tween axle and spring etc.
Paul Hunt

As I recall, it's also a bit of a job removing the shackle itself on one side because the fuel tank is in the way.

Neil
Neil

Thanks for all the suggestions. I did the job this weekend and have to say it was a complete nightmare. The problems were due to the fact that I decided to use blue polybushes which, for the front eye of the spring, were just a so hard to install.

My suggestion if you ever try installing polybushes in the front end of the leaf is as follows:
1. Get a long piece of threaded bar a couple of nuts and some thick washers - as big over as the bush on one side and as bigger than the hole it's going through on the other.
2. Use the bar, washers and nuts to pull the bush through into the hole and wind it through as far as it will go.
3. For the final bit to pull the push complete through, I used a 2 leg puller again with a washer behind the bush to force it through that last bit.

Anyway, job almost done now so it will be interested to see how the car runs with an all polybush setup.
JH

Ah yes Neil, it depends on which way round the half with the pins is installed I think. If it is in the easier way it shouldn't be a problem getting the nuts undone (any more than any other nut). I've swapped springs around at least four times on various cars and didn't have a problem other than the more limited space.
Paul Hunt

Paul, you don't need to take off the straps or undo the U-bolts to change the shackle bushes, simple jacking is sufficient. The max torque for the U bolt nuts is 25ft/lbs. 55 will well and truly strip them
Iain MacKintosh

Iain - jacking where? The springs are under a lot of bending force even when the axle is hanging down on the straps, and even if you could remove the shackles the rear eyes would immediately snap up to the chassis rail. You would then have to lever the eye back down with some considerable pressure to get the shackle back in again. You do have to jack up under the spring so the eye slides backwards along the chassis rail far enough to get the shackle installed, but it then needs quite a bit more jacking before it reaches the axle. That's what I've always found, anyway, but then I've been replacing springs and not just rear bushes. Both the Workshop Manual and Haynes imply that there is no tension left in the spring by lowering the axle, but that is with the drop-link and rebound rubber removed. I've never liked to rely on that as the lower limit of the axle on the RHS at least is then the brake flex hose.
Paul Hunt

Paul, I've previously jacked the reinforcement plate and placed another jack under the axle for support. When the shackles are removed the spring tended to fall and not go up and hit the chassis rail. If they do go up then they can be levered off by using a tyre lever between the spring and the rail. I've replaced bushes on their own and found it a straightforward job.
Incidently I would tend to put some Silicon grease on the bushes and espacially on the pins to ease assembly and prevent squeaking.
Iain MacKintosh

I'm almost finished replacing the rear leaves and used the polyurethane bushings throughout. Getting the front bushing out isn't that tough. Note that it's a circular "eye" and there is a gap where the eye meets the leaf. I used a cold chisel in the opening and spread the eye open a bit (a common screwdriver could be used also). The old bushing came right out and the new one went in easily then I pulled the chisel out and the eye closed. It doesn't take much spreading to release the pressure and do this. The springs were completely dropped and probably easier to do this operation since I could set it on concrete and drive the chisel in easily. Might be tougher while on the car. The rear shackle by the gas tank doesn't have enough clearance to drive out with a hammer. I backed the nut most of the way out, but left it to protect the bolt threads then used a 6 inch clamp (wood working tool) to push the bolt out enough to do the rest by hand.
Rick Penland

This thread was discussed between 07/11/2008 and 14/11/2008

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