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Trunnion bushes

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bigjones

bigjones

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MGTrunnions.jpg

Courtesy of Moss Motors

Trunnion bushes are item #7

Jim Horton wrote:
"To just replace the trunion bushings requires putting a floor jack under the A arm to keep compression on. Remember, you've got the coil spring there pushing the other way. The castellated nut comes off as well as the pinch bolt at the end of the shock arm. Pick up a can of PB Blaster and start soaking all the nuts and bolts."

Does this procedure involve any safety issues? I'm not sure I like the idea of compressing that big spring.

Cheers,
Adrian
 
No safety issues. The weight of the car keeps the spring compressed, even if you were to have a jack stand under the chassis and let the jack down the spring would not forcefully come out.
 
Adrian-Before I tackled the suspension job I was apprehensive about using the jack method to relieve coil spring pressure. After I did one side I realized my fears were for naught, and it's a lot easier to take the suspension down. Are you just replacing the trunion bushings, or going further? Hopefully I still have some of the experience left in my brain cells to help you if need be.
 
Jim,

Thanks for the post.
Right now I plan on just replacing the trunnion bushings as they definitely look ragged.
Prolly more stuff there that needs replacing but I'm thinking one thing at a time.
There is some play when I rock the tire, holding it top and bottom.

Cheers,
Adrian
 
Either bearing or (most likely) worn fulcrum pin/bushings.
 
Just a little tip: If you let the jack down after removing the top trunnion, put a 1" piece of wood between the damper arm & the chassis. Then the damper arm does not squash the heck out of the rubber bump stop.
Also: Replace with SuperPro Polyurethane bushes. They are soooooo much firmer & will greatly reduce the play.
I've just been to Autosport show here in UK & seen the guys who make these, & played with a Rover rubber bush verses a SuperPro Polyurethane bush. No contest. Polyurethane bushes for me everytime all round.
 
NB. I've just replaced the whole lot at the front end. New king pins, bushes in hub, fulcrum pins, wishbones, all bushes. Wheel bearings. It now feels real tight & smooth.
Added plenty of lovely lithum greese.
Can't wait for some spring weather to give it a good thrapping.
 
Trunnion bushes - Help!

FulcrumPinBushes.jpg


Well, I have sprayed with PB Blaster, took out the cotter pin and undone the castellated nut. Undone the clamp bolt (more than in the photo) until it reached the brake rotor.

I tried pounding on the end of the castellated nut (protected with a piece of hardwood). Nuttin' honey.

Tapped the nut with a hammer and the fulcrum pin must have moved about 1/8".

I was kinda hoping the fulcrum pin would obligingly fall out, along with remnants of the rubber bushes but nay.

I'm still a bit cornfused about the need for a floor jack under the spring. I put one there but when I tried to apply a bit of pressure, the car started to lift off the jack stands so I didn't use it. Instead I put it under the disk rotor as it seems to me that that is going to need support if I can ever get the fulcrum pin out.

Seeing as I don't know what I'm doing, I thought I'd better ask what to do next.

Cheers,
Adrian
 
Re: Trunnion bushes - Help!

That bolt has to be totally removed from the shock.
 
Re: Trunnion bushes - Help!

Trev,
The clamping bolt is out about 1/2" but then its hitting the disk rotor so I can't fully extract it.
I'm stuck.
 
Re: Trunnion bushes - Help!

Turn the steering wheel? Jack up that A-arm?
 
Re: Trunnion bushes - Help!

Doh!

OK, turning the steering done the trick! The clamp bolt is out now.
I kept the castellated nut on and tapped it with a hammer to the limit. Now I am using a nail punch to drive the fulcrum pin out.
Before I give it the last tap, can you tell me what will happen next?
Does the disk assembly fall away and the shock arm remain where it is?
I have not used the trolley jack.

Just checking.

Thanks,
Adrian
 
Re: Trunnion bushes - Help!

Yes it will fall away and potentially damage your brake hose. Either remove the caliper or have something to tie the assembly up to keep it from falling that far.
 
Re: Trunnion bushes - Help!

NewBushes.jpg


OK, starting to make sense. Thanks.

Last question - as you can see I'm putting in polyurethane bushes. Should I discard the metal "top hats" (one seen still on the fulcrum pin and the other bottom left) that came with the old rubber bushes?

Cheers,
Adrian (happier)
 
Re: Trunnion bushes - Help!

yes, discard, the old metal is no longer required
 
Re: Trunnion bushes - Help!

No metal with the new poly bushings.
 
Re: Trunnion bushes - Help!

You'll also notice the fulcrum pin is slotted. It only goes in one way so the other bolt can be inserted and tightended in place.
 
Re: Trunnion bushes - Help!

CotterPin.jpg


Thanks for the help - the new bushes are installed. And all before midnight.

I do have a couple of concerns though, regarding that castellated nut, that maybe you could comment on:

1. The size of the cotterpin securing the nut is awfully thin. I tried it out on the bench and picked the thickest one that would fit but still it is worrying to me that it is not what you would call stout.

2. In order for the cotterpin to actually go through the castellations of the nut, I had to use a (grade 8) washer under the nut, otherwise the cotterpin would be above the nut.

3. Haynes says the torque on the nut should be 40 ft.lbs.
But then I had to back it off (to the stage where it is not particulary tight) in order for the cotterpin to go through both nut and fulcrum pin. I could not go the other way and tighten it some more past 40. I did use Locktite.

4. Something I keep wondering about - I think I read someplace that the proper technique is to bend over just one of the legs of the cotterpin. Doesn't make much sense to me, unless you intend maybe to re-use the pin but that is a total no-no these days.

Am I good to go?

HEY!! I used crocus cloth on the fulcrum pin to clean it up - do I get exra credit??

Cheers,
Adrian
 
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