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Best CV driveshafts?


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My car has quite pronounced Triumph Twitch. Looks like the rear end is ready for a good coat of looking at. New CV driveshafts are a tempting fit and forget solution. 

Looks like I have two options, Limora, or CCD, bit put off by the former due to the faff involved matching the hub to halfshaft using engineers blue. Any other makes I should consider?

Thanks 

Sean 

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Fitted a set of CCD driveshafts to my TR6 last winter and also updated the trailing arms to the stepped stud arrangement. Very happy so far. Also fitted a set to a customer’s Stag which he reports to be very good. 
 

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Got CDD shafts.  Did the rbrr with them. Easy fit and so far seem good.

Tim

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Richard. As standard the rear hub carrier is attached to the alloy trailing arm with 6 studs which are 5/16 in diameter and carry a UNF thread. Over the years successive removal and refitting of the 1/2 in nyloc nuts has a tendency to damage the thread tapped into the alloy. Many on these forums will comment on the result of these studs failing. Not a good experience. Repair of the alloy trailing arm threads can be achieved by hellcoil inserts. A better solution is to enlarge the threads to 3/8. A stepped stud is then needed that is 3/8 dia to screw into the suspension arm and 5/16 at the other end to pass through the hub carrier and receive the 1/2 in nuts. CCD do a kit to address this issue. 

Edited by Mike Herlihy
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I just used helicoils. Worked well and feel secure. 

Tim

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15 hours ago, Mike Herlihy said:

A better solution is to enlarge the threads to 3/8. A stepped stud is then needed that is 3/8 dia to screw into the suspension arm and 5/16 at the other end to pass through the hub carrier

Why is that a better solution? The helicoils are effectively a 3/8 UNC thread in the alloy. The original 5/16 UNF stud is plenty strong enough, and screws into the internal (5/16 UNF) thread of the helicoil. Also, less chance of damaging an alloy thread in the unlikely event you need to remove the stud in future.

I see no advantage or disadvantage with either approach. And helicoils are easy to source. Are stepped studs? The last I used were custom made by my father in 1980...

John

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“Why is that a better solution? “

Because in the trailing arm the securing “ lugs” for the 5/16 UNF were positioned by a 3 month in service apprentice… who was drunk !

There are multiple examples ( I’ve seen 3 ) where replacing the original thread with Helicoils leads to the peaks of the new thread breaking through the sidewalls of the lug leaving an unsupported edge…not ideal. So any protecting of the original material around the studs, no matter how little is to be encouraged. 
In contra intuitive leap let me state that a 5/16 UNF helicoil requires a greater hole dia be drilled for the core dia  - .328 thou. Whereas a 3/8 UNC tapping size hole is only - .312 which is 5/16” which is the size the studs are tapped at in the trailing arm, which is the remains in the pile of grey dust which comes out of the hole. Often you don’t even have to drill the hole, it’s ready to accept a 3/8 UNC tap. 
Some pedants would argue that saving the wall thickness by a small amount of 16 thou overall dia is pointless, however better in the hole than on the floor is how I reason it.

Ohh, and the studs don’t need to be stepped, drill out the hub flange to accept 3/8” UNC and replace the studs with 3/8 UNC cap heads through the hub and into the trailing arm parent thread you’ve just tapped. Cheap and freely available, that’s what the racers do.


Mick Richards

Edited by Motorsport Mickey
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Thanks for the explanation and understood.

My only comment is that I'm surprised that the hub carrier is actually removed that often. My car has done 61,800 miles and whilst it was supposedly previously restored (very badly and probably just the bodwork), I'd be surprised these were ever removed then.

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Richard,

These cars are now 50 years old and although your example has only 62,000 miles on it (hopefully correct) the passage of time causes many of these problems.

The reaction between the disimilar metals of the trailing arm (alloy) and the securing bolts (steel), causes the alloy threads to corrode and it's not unusual as you start to undo the bolts to see granular grey material (the threads)falling from the hubs as the bolts are wiggled being undone. I'd put the chances of an original car of being able to undo all the retaining nuts and hubs and have all studs still left in the trailing arms hub faces or without thread damage as unlikely. The torque requirement for these nuts on the hub retaining bolts are low, only 16 lb ft (from memory) but it may be that on the many low mileage cars there is less retained clamping on these hubs than drivers may like.

Mick Richards

Edited by Motorsport Mickey
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18 minutes ago, stuart said:

FWIW the original torque setting for the studs is 16lbs.

Stuart.

Thanks for the correction Stuart, I've edited my post.

Mick Richards

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12 hours ago, Graham said:

they are nice, but expensive and require a much larger hole to be drilled. So be careful where you use it.

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Thanks again for comments. Minor point but of my car's 62k, only 700 has been done since 1981 (have USA failed MoT cert). So that means 40 years of sitting in Virginia, somewhere but under cover albeit not totally in a damp proof environment.

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22 minutes ago, astontr6 said:

Stuart, what do the people like yourselves do to cure this problem?

Bruce.

Depends on how bad they are, usual go to is a helicoil. I did have to replace one trailing arm due to a previous repair where on a couple of studs that had obviously failed previously some back street garage had drilled right through and put a Metric nut and bolt in :wacko::o

Stuart.

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If you are not in a rush, I have had quite a lot of success removing the trailing arm studs without damaging the TA threads - I remove the TA and hold it so the the studs and flange are vertical and then regularly dose each stud with a quality penetrating oil such as Plus-gas (not WD40!) daily for typically a week.

Following this the studs nearly always come out cleanly with the threads in the TA intact - it's only failed on one TA when I was in too much of a hurry and didn't dose the studs for long enough and 2 studs stripped their threads - not saying it's always perfect but it's worked for me and saved a lot of helicoiling.

I always rebuild with new studs and torque up to 16lbs/ft with an accurate low scale torque wrench, and have never had any of the threads fail, so I'm pretty confident this works OK

Cheers Rich

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On 10/23/2021 at 10:04 PM, Motorsport Mickey said:

In contra intuitive leap let me state that a 5/16 UNF helicoil requires a greater hole dia be drilled for the core dia  - .328 thou. Whereas a 3/8 UNC tapping size hole is only - .312 which is 5/16” which is the size the studs are tapped at in the trailing arm, which is the remains in the pile of grey dust which comes out of the hole. Often you don’t even have to drill the hole, it’s ready to accept a 3/8 UNC tap. 
Some pedants would argue that saving the wall thickness by a small amount of 16 thou overall dia is pointless, however better in the hole than on the floor is how I reason it.

Ohh, and the studs don’t need to be stepped, drill out the hub flange to accept 3/8” UNC and replace the studs with 3/8 UNC cap heads through the hub and into the trailing arm parent thread you’ve just tapped. Cheap and freely available, that’s what the racers do.

Thanks - that makes sense. BTW, is the same 16 ft-lb torque correct for the cap heads?

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48 minutes ago, JohnC said:

Thanks - that makes sense. BTW, is the same 16 ft-lb torque correct for the cap heads?

Yes John, I believe that's what used.

Mick Richards

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