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Post by Muzz On Line on Jul 6, 2019 17:30:52 GMT 10
Hi Guys,
Whilst touring Tassie last year, the tug developed (over time) some clunking on take off. Now as a lot of you know, the Australian Government took all the bends and hills out of outback Queenslands' roads and had them installed in Tassie. In return they took all the shoulders off Tassie's roads and put them in the middle of paddocks in Queensland. But I digress.
When I was able to get under the tug and have a look around I discovered the tow bar bolts had loosened. I did not have a torque wrench with me so I just tightened them as best I could. Now after a bit more trekking around, they appear to be a bit loose again.
My tow bar consists of flat plates from the chassis, approx. 140mm square tubing with plated ends bolted between the plates that come off the chassis, and the receiver for the tongue coming off the tube. This is a standard factory 3500kg rated towbar. The bolts that were loose were the bolts used to connect the 140mm square tubing plates to the plates from the chassis.
My questions are -
should I replace these bolts or just re-tighten them to the correct torque?
what is the correct torque?
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Post by Old Techo on Jul 6, 2019 17:45:36 GMT 10
How many bolts total in affected the group?
How many were loose?
Are they high tensile bolts?
What is the bolt diameter?
Metric or imperial thread?
Coarse or fine pitch thread?
Do they have spring washers or Nyloc nuts?
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Post by Mick Themungrel on Jul 6, 2019 17:50:19 GMT 10
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Post by nsgnomad on Jul 6, 2019 17:52:20 GMT 10
Here's a thought. Is the Chassis hollow where the bolts pass through, and so possibly crushing the chassis? Do you need to use spacers to prevent this?
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Post by GerryP on Jul 6, 2019 17:53:32 GMT 10
Here's a thought. Is the Chassis hollow where the bolts pass through, and so possibly crushing the chassis? Do you need to use spacers to prevent this? Just had a similar thought and certainly worth checking.
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Post by Muzz On Line on Jul 6, 2019 17:58:38 GMT 10
How many bolts total in affected the group?
How many were loose?
Are they high tensile bolts?
What is the bolt diameter?
Metric or imperial thread?
Coarse or fine pitch thread?
Do they have spring washers or Nyloc nuts?
Jeez OT, I will try to answer some but it is pitch black outside, raining and cold. You may have to wait for a couple of answers. First occurrence was over a year ago, so relying on dodgy memory.. 4 bolts per side so 8 in total. From memory, all were loose. It was like the paint on the surfaces where the bolt heads and washers touch the plates was worn away. The next 4 questions are bit harder. From memory I believe they were High Tensile as I think there were tell tale marks on the bolt head to reflect that. Approx.10mm with locking washers. Not real sure here as I did not take them out, just tightened them. Cannot recall thread type or if metric. This is a Factory fitted Mazda / Ford towbar.
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Post by Old Techo on Jul 6, 2019 17:59:18 GMT 10
I reckon if there was a hollow section involved it would begin to crush well before any decent torque was reached and the tightening 'feel' would be quite apparent to the spanner man.
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Post by Muzz On Line on Jul 6, 2019 18:05:25 GMT 10
Here's a thought. Is the Chassis hollow where the bolts pass through, and so possibly crushing the chassis? Do you need to use spacers to prevent this? Just had a similar thought and certainly worth checking. Thanks Guys, but no there is no crushing of the chassis. The bolts that were loose are on the plates that are bolted to the chassis, but not the bolts used to bolt the plates to the chassis. These plates lower the cross tube with the receiver to the correct (for lack of a better word) height.
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Post by Muzz On Line on Jul 6, 2019 18:09:25 GMT 10
Thanks Mick. I think for piece of mind I will go to a proper nuts and bolts shop and get identical replacements just to be sure. They should also be able to give the correct torque to use. Thanks guys Just needed a sounding board to get me off my ar... rear.
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Post by Muzz On Line on Jul 6, 2019 18:18:31 GMT 10
Just for clarification, the bolts circled are the bolts I was referring to -
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Post by GerryP on Jul 6, 2019 18:26:54 GMT 10
I have a Milford bar for my Ranger in the shed and I'm sure it's welded where yours is bolted. I changed it when I first bought the ute as I was not overly impressed with the very short receiver on the Ford bar.
I've since replaced it with an Ironman rear step bar, so it's now surplus.
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Post by nsgnomad on Jul 6, 2019 18:32:54 GMT 10
Muzz, you mentioned 10mm for the size of the bolts. I thought this might be a bit light so I just went to check my vehicle. Now admittedly a different style of towbar on my LC100 but mine is held by thicker bolts. I can't see the shaft of the bolt but the head is 22mm across the flats and is high tensile, stamped 8.8 so I am guessing it is probably 14mm dia. 3 of these on each side positioned vertically up plus 1 horizontal (I think from memory 12mm) through the box chassis. I have checked the tension of these bolts over the years and never found them loose. I did have to remove the towbar when I fitted a rear wheel carrier/bumper, but once reinstalled, never showed signs of loosening.
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Post by nsgnomad on Jul 6, 2019 18:39:37 GMT 10
Just looked at the photo of your towbar and yes different requirements for the bolts compared to mine. On yours the load is mostly shear whereas on mine it is in tension. But, is there any possibly of slight flex on those side bits that actually bolt to the chassis. It might be the flex that is causing the bolts to loosen.
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Post by Muzz On Line on Jul 6, 2019 18:46:31 GMT 10
Thanks mate, I was only going by memory and 10mm does sound pretty small. Must admit I did not remove them so have not actually seen the bolt diameter.
Just remembered that I had to borrow a large spanner as I needed 2 and only had the one that fit. 22mm does ring a bell but then again with all the noises in my head, bells are the least of my worries.
Seriously though it did seem at the time that the paint thickness was the cause of the looseness. There were some pieces of paint chip sticking out on one of the bolt heads which was how I found the loose bolts. Could be why they are loose again as I did not clean them before re-tightening.
I know now so when I replace them I will clean first and then paint them when finished.
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Post by Old Techo on Jul 6, 2019 18:57:04 GMT 10
Jeez OT, I will try to answer some but it is pitch black outside, raining and cold. You may have to wait for a couple of answers. First occurrence was over a year ago, so relying on dodgy memory.. 4 bolts per side so 8 in total. From memory, all were loose. It was like the paint on the surfaces where the bolt heads and washers touch the plates was worn away. The next 4 questions are bit harder. From memory I believe they were High Tensile as I think there were tell tale marks on the bolt head to reflect that. Approx.10mm with locking washers. Not real sure here as I did not take them out, just tightened them. Cannot recall thread type or if metric. Muzz,
I asked those questions as dimensions need to be known to determine the correct torque.
If the towbar was loose enough for 'clunking' to occur the bolt holes may have enlarged slightly and bolt shafts worn a bit too increasing the lash or slack in the junction.
Certainly get new high tensile nuts, bolts and spring washers. You could put a blob of 'whiteout' (correction fluid) on the nut/bolt thread junction so that next time if loose again you can tell if the nut has moved on the bolt or the bolt has stretched a bit.
I check my Prado genuine Toyota towbar 6 bolts every year and get a fraction of a turn on some.
The popular white rims used on caravans are known to lose some wheel nut torque due to the thick paint wearing between the wheel centre and the hub.
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