QL5000 type joint failure

[jayare]

As I mentioned in the AA thread last weekend I had a failure of one of the QL5000 joints on my Mini Pickup. I ordered a replacement pair from Minispares and have fitted them this afternoon but just want to check I haven't made any howlers. The joint which failed ended up looking like this:

IMG_0820 Small.jpeg

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I noticed on the remaining joint it looked like a couple of the nylon cups had moved 'outwards' leaving a small gap between the internal step in the nylon cup and the UJ. Now was this due to me over-tightening the U-bolts when I had the engine out to change the final drive a couple of months back? Or maybe the opposite - not tight enough? The nuts weren't particularly tight on the intact joint when I undid them although with nylocs it's always a little difficult to tell. The intact joint didn't show any signs of damage but I replaced both for peace of mind and due to the cups having seemed to have moved.

For the moment I have fitted the two new joints with the nuts done up with my short spanner (about 2.5" long) and the nylon cups look to be sitting nicely in line with the edges of the yokes. I have only given it a short run round the block for the moment - any advice/help on this would be appreciated.

JR

[Spider]

I haven't fitted these for a long while, but just looking at where your nuts are I think they may have been way too tight.

[dklawson]

That looks awful. I have not read the other thread but I hope there was not too much damage other than the joints.

The old QL5000 kits instructions included a torque spec for the nuts. I always thought that spec was ridiculously low considering that the nuts had deformed threads so they would remain in place.

[jayare]

Fortunately no damage other than the joints and a small scuff on the exhaust - probably as it broke as I pulled away onto a roundabout so very low speed.

In terms of the position of the nuts, the replacement joints with the nuts snugged up to the yokes plus less than 1/2 a turn look pretty similar - really bad photo but this is the replacement joint:

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The replacement joints were from Minispares and had no instructions or torque settings in the box and there is no torque info on the product page on the website either, hence checking on here that I'm in the right ball-park. Anyone know what the torque setting should be? Not sure how I'd get a torque wrench in there to check them mind you!

JR

[ricardo]

IIRC the original QH5000 are 7lbft and I agree with Doug. When I fitted mine 5 years ago, and if I remember, I could only squeeze a spanner, no chance for a torque wrench.

I've seen something similar on a friend's car using MS replicas as well, but I assumed he had them too tight. He changed to rubber couplings then. Impressive how your U fittings are bent. I have a MS set to fit soon too, hope that doesn't happen

[rich@minispares.com]

The u joints will bend when the joints fall to bits though, I've managed similar carnage before with both the ql5000 and rubber Maltese falcons!

[agricola]

I had these on my s in the 70s, but I think they were steel not nylon?

[dklawson]

I had these on my s in the 70s, but I think they were steel not nylon?

These black ones are the new version currently in production.

The original ones from years ago were made of white nylon. Yes, there were steel ones available also. I don't know who made them but I have a set.

A decade or so ago someone was selling a version made of green nylon. Over the years people have also tried making them in aluminum.

[Spider]

Just one other thought I had for a possible cause here is a bent dive shaft or something else to make the shaft run out of balance.

[tmsmini]

These are the instruction on the outside of the box. Not sure what year they are from, but awhile ago.
Terry

[kit of bits]

Just one other thought I had for a possible cause here is a bent dive shaft or something else to make the shaft run out of balance.

Could be you had a big vibration at one point..
D

[Mini4Ever]

Hmm, I have NOS white ones for most of my cars and hope they do last. Don't want to ruin the gearbox casings... Picture of instructions is by the way showing ADO16 suspension

[Peter Laidler]

I would guess that it's the low torque figure for the nuts that's part of the problem. Most do-it-yourselfers would doubt the veracity of the 8ft/lbs torque figure and triple it. Overtighten at your peril because the nylon joint will only move one way - and that's OUTWARDS, assisted by centrifuge. And you can never beat the laws of physics

[jayare]

Thanks all for the input. Spider - I'll check the driveshafts for run-out to make sure they are straight but it will likely be next weekend as I'm working late shift all week (today and BH Monday included )

Looking at the QH instructions (thanks for posting tmsmini), they mention putting the washers and nuts on hand tight, suggesting they originally came with plain nuts (and spring washers?) rather than the nylocs currently supplied. A torque figure of 8lb-ft is very low - what would the torque required to overcome the friction of the nyloc be? Still no idea how I'd be able to get a torque wrench in there to set them!

JR

[timmy201]

I did the same, while going about 110kph down a hill. Both sides broke and I had to get towed. I think I was only able to find 3 of the nylon cups when I got home, the flailing driveshaft also scratched the gearbox and exhaust manifold

[dklawson]

I would guess that it's the low torque figure for the nuts that's part of the problem. Most do-it-yourselfers would doubt the veracity of the 8ft/lbs torque figure and triple it.

I am sure you are right Peter but the problem is a bit deeper than that. The instructions posted specify the torque as 8 ft-lb and the text implies (as others have said) that the original installation from the 1960s appears to have used plain nuts and washers.

I have seen kits with both distorted thread nuts and nylok nuts. Neither of these can be done up "finger tight" as the instructions say. Further, it can take almost 8 ft-lb just to run these nuts up the u-bolt threads. If the running torque of the threads approaches the final assembly torque, almost no clamping force will be present in the end.

Also as mentioned earlier, there is not really enough room to get a torque wrench in there. Perhaps a torque wrench with a crows foot wrench could work if the car is elevated enough. Otherwise you have to use a traditional wrench and tighten by feel. Incidentally, 8 ft-lb is about what you would apply as standard torque for a 1/4 inch fastener.

Regardless, if you want to follow the original instructions you probably need to replace the nice nylok nuts with plain nuts, washers, and Loctite.

[Peter Laidler]

Interesting thread......... Discussed it this afternoon at a car show with one of my course mini owners. It seems as though it's not an uncommon failure. So I'm really thinking out aloud now........ I can see exactly where you're coming from Doug. The initial torque load threading a locknut onto bolt is easy(?) to ascertain off the car. But it's difficult for a non-engineer at home - or someone pretty proficient - changing bits of the drive train at home to believe that something important in the drive train required 8 important yoke bolts to be loaded up to an almost insignificant 8 lbs./ft. It almost alien.... The answer must be to add the initial thread torque loading to the 8 lbs./ft spec figure and use that AND NO MORE when tightening up the yoke bolts.

How you do it when you can't get a torque wrench on...... That's where finger tip experience comes in. But the carnage that over tightening can cause isn't worth thinking about

[CooperTune]

I purchased a set of the new QL 5000 joints. I found the groove machined in the plastic for the U bolt to be in the wrong position. I threw mine away and converted to pot joints, I don't have time to rework everything I get. Steve (CTR)

[iain1967s]

The current black cap replacement QL5000 style need fettling to fit properly. 7ent have some guidelines here: https://www.7ent.com/products/drive-sha ... s0024.html but I gave up and reused the original white nylon caps.

[mullerm]

I fitted then original ones 20 plus years ago and must say have had no problems at all with them plus they have had some stick in that time, so last year during a front end rebuild over the winter i thought i would replace them with a new set from Minispares. All has been ok till last week end i noticed the o/s side one was touching the center exhaust of the LCB and had melted a bit, took off to check and all 4 plastic cups fell off leaving the needle race bearing still fitted to joint, checked the n/s and though no signs of damage when taken apart the cups again just fell off. I have since fitted back the original ones and so far all is ok, question is what are the black plastic cups made of, the original were nylon and look fit for purpose the new black ones dont, the Hardy spicer joint itself is perfect. If i remember right i had issues when i tryed to fit the new ones and rang minispares about it, it turned out the needle race was not inserted into the black plastic cups fully so i had to press them in further to be able to fit the coupling to the yokes. As regards tightening the nuts to the correct torque may be i did over tighten, its not easy as many of you know to torque up to 8 ft ibs but the original ones had been on and off during rebuilds etc and i had no problems at all, i was younger then and it was a case of get them on quick so i could go and play! i was lucky the coupling did not fail on the run as it could do loads of damage but i think any one who has fitted these new couplings should check them often for signs of fatigue