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PYU940F

Trunion bolt torque setting

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Hi,

This has been discussed before. When I overhauled the font suspension on the 4a I could not find a torque setting for the trunnion bolt. The only information in the workshop manual is for the 4 which has a different arrangement with bosses on the trunnion, not a through bolt. For the 4 it is 5 ft lbs and then backed off 2 flats. That is really quite loose. This forum suggested that the 4a is the same as the 6 and the 6 manual says about 50 ft lbs.and that is the setting I used. My front suspension is jaw breaking hard even with the shox set on full soft. I am going to progressively loosen the nut starting with about 25 ft lbs. Has anyone else had this problem?

 

Thanks

 

Simon

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Hi Simon, according to the workshop manual

" The lower fulcrum bosses must have 0.004"-0.012" end f!oat"

Tighten the slotted nut to 5 lbs ft and slacken off 1-2 flats and insert split pin.

This is TR 4A but design is same for TR6 and similar on TR2/3 except they have two slotted nuts which are set separately.

Looking at the components if you just torque them up they will go solid which is what you have at moment.

Chris

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Hi Simon, the idea with the 4A to 6 trunnion setup is that each spacer (Pt.139832) is supposed to rotate within the nylon top-hat bushes (Pt. 139833) and be kept in place by the thrust washers (Pt. 142388), in order to do this the through bolt has to lock the spacers against the trunnions, (this can only be achieved if the spacers and thrust washers have been machined to the correct dimensions and the through bolt is done up with sufficient torque, if not then the trunnion will rotate on the through bolt and the top-hat bushes kind of become redundant.

Cheers Rob

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Thanks guys but 2 different views on the problem. Chris says tighten as per the 4 set up (5 ft lbs) and Rob says tighten as per TR6 set up (50 ft lbs). What I will do is jack up suspension and disconnect the vertical link from the upper wishbones. I can then test how free the movement is in the rotation of the vertical link around the trunnion bushes. Rob also mentions that there should be no movement between the bolt and the trunnion. Surely a small amount of movement is not a problem, it was well copper slipped on assembly.

The other solution is maybe put poly bushes in instead of the top hat plastic bushes. Has anyone done this?

 

I did notice on re-assembly that it was impossible to tighten the trunnion before lining up the lower wishbone studs with the chassis holes. It all had to be loose assembled and then tightened. Is this normal as a fair amount of tension would be put on the trunnion assembly

 

Cheers

 

Simon

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For TR6, when rotating the vertical link, the bolt with castellated nut MUST turn with!

The castellated nut is torqued according to the manual.....don't have it a hand...but is certainly around 50 ft lbs and not 5 ft lbs.

Jochem

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For TR6, when rotating the vertical link, the bolt with castellated nut MUST turn with!

The castellated nut is torqued according to the manual.....don't have it a hand...but is certainly around 50 ft lbs and not 5 ft lbs.

Jochem

Yes, just what I said, the trunnion, spacers and bolt locked together so that the turning motion is within the plastic (or poly) bushes, not the trunnion turning on the bolt, it will wear through and go oval.

Rob

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Guys whilst not disagreeing with the principle on how the set up should work I have in front of me the Moss parts catalogues with the exploded views for both TR4A and TR6, the list of parts making up this assembly is identical for both cars including the Trunnions.

I have a TR4A workshop manual but not one for a TR6, can someone who has a TR6 manual advise if the assembly method is different for the same parts as TR4A and that the 50 lbs ft torque applies to this bolt. Has a zero either been added to the TR6 manual in error or left off the TR 4A one.

 

As the TR4 bolts are part of the trunnion assembly then maybe the 5lb ft applies only to the TR4 as this would work as they can't pivot, and therefore the TR4A manual could be wrong by inferring the 5ft lbs is for both models.

Stuart can you throw some light on this please.

Chris

Edited by potts4a

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Unfortunately the manual is basically for a 4 with a few additions for the 4a and the section on the front suspension for the 4a is pretty skimpy and doesnt contain any torque settings

Stuart.

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It's 10 years since I fitted the super pro bushes and I have not had to touch it since but will be looking tomorrow to see if bolt is locked to trunnions when suspension lifted. I have noticed no play and it's done over 30000 miles since I replaced the bushes. I will report later.

Chris

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Hi everybody,

 

I vote for "on TR4A as on TR6", torque is just "tight" on my TR4A, nothing special.

 

The trunnion, four steel washers, both steel bushes, the bolt and nut have to be one locked unit.

The POM bushes pressed in the lower wishbones have to slide on the steel washers.

 

This does not work,

 

- if the steel washers are too short

- or the steel washers are made of mild steel

- or there is too much paint or pouder in the wishbones

 

Ciao Marco

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ups, I knew I told that already at this forum, sorry me ... :-)

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Well I just checked my 4A by marking the bolt head / washer and wishbone with a straight line and then jacking the car up so the wheels dropped down. The trunnion, bolt and washer are staying aligned and the wishbone is moving round so it's working correctly. As it's about 10 years since I fitted the polybushes I can't remember exactly how tight I ended up doing the bolts but I do remember putting plenty of the supplied grease on the assembly.

Chris

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