• Scam Alert. Members are reminded to NOT send money to buy anything. Don't buy things remote and have it shipped - go get it yourself, pay in person, and take your equipment with you. Scammers have burned people on this forum. Urgency, secrecy, excuses, selling for friend, newish members, FUD, are RED FLAGS. A video conference call is not adequate assurance. Face to face interactions are required. Please report suspicions to the forum admins. Stay Safe - anyone can get scammed.
  • Several Regions have held meetups already, but others are being planned or are evaluating the interest. The Calgary Area Meetup is set for Saturday July 12th at 10am. The signup thread is here! Arbutus has also explored interest in a Fraser Valley meetup but it seems members either missed his thread or had other plans. Let him know if you are interested in a meetup later in the year by posting here! Slowpoke is trying to pull together an Ottawa area meetup later this summer. No date has been selected yet, so let him know if you are interested here! We are not aware of any other meetups being planned this year. If you are interested in doing something in your area, let everyone know and make it happen! Meetups are a great way to make new machining friends and get hands on help in your area. Don’t be shy, sign up and come, or plan your own meetup!

How to measure high torque values?

The original question was how to measure the torque on the bolt. Certainly force x distance, as others have suggested, works well. There have been several good comments about addressing the “clunk”, about which I would know nothing - so I leave that to others.

There are two other pretty common approaches to measuring “bolt load”. The intention of torquing a bolt is to achieve a certain load on the bolt (generally one should be consistent about that). Most bolted joint designs are targeting joint load, which leads to a certain bolt load, as pounds per square inch in the bolt material. Using torque on the fastener is simply one way to determine that bolt load (quite a poor method because friction plays a large role and several factors influence how much friction there is).

In basic terms, to achieve a given stress in the bolt material, you need to stretch the loaded portion of the bolt a certain amount (think Young’s modulus). Start out by calculating how much bolt stretch is needed to get a given bolt load (say 50% of the yield strength of the bolt).

One approach to determining how much stretch is applied is called “angle of turn”. Since you have a target elongation and know the pitch of the thread, just calculate how much to turn the nut to achieve that much stretch. The procedure is to start at a nominal torque value (quite low, thus friction force is low), then turn the nut through that angle.

A second common method of determining elongation (thus bolt load), is to simply measure the before and after bolt length. In practice the bolt ends need to be cleaned up (faced flat), then measure bolt length anyway you want. In industry the usual method is time of flight ultrasonic (only need access to one side, fast to do) - but regular calliper is totally acceptable.

Seems like over kill for a shock mounting bolt - but you asked, so there you go.
 
Chipper5783 said:
Seems like over kill for a shock mounting bolt - but you asked, so there you go.
Click to expand...

Not really. I do have the benefit of having taken a number of specialized courses on fasteners in automotive applications. You are right about the how and the objective, but there is much more to it than that. Normally, I might just let your explanation stand since it is correct. But in this case there are other factors that might make this particular application very different. Please forgive my non-scientific jargon, it's there for simplicity.

Why a target torque? Usually, it is to prevent the fastener from coming loose over time. A certain amount of stretch as you describe creates a normal stress in the threaded section that is greater than the friction. As long as the normal stress/stretch doesn't exceed the ultimate strength of the material, the nut won't move and come loose because the stretch force is greater than the friction force. Usually the stretch force capacity is significantly higher than the friction force so a range of acceptable torques is just fine. These are the so-called easy fasteners. Torque them sufficiently to exceed their loosening force and call it done. These are the torques you see listed on fastener websites and product manuals.

However, there are a number of other situations that are much more complex.

A good example is single use cylinder head bolts. These torque to yield bolts are deliberately stretched beyond their yield strength in order to ensure extremely consistent clamping and sealing. It's better than using a friction based torque setting because of the consistency. I believe this is exactly your point about direct stretch measurements.

But let's move beyond that to other situations where that doesn't work. A good example is wheel studs and nuts. 99% of broken wheel studs don't break from over tightening, they actually break from under tightening. The root cause is excessive load cycling of the bolt. The cycling causes fatigue, the bolt cracks, the crack grows, and eventually the cross-section falls to a level where the stud breaks. I believe we discussed this at length elsewhere on the forum.

Another example is sleeved joints where the sleeve must not turn but another component must be free to turn.

If I were asked to guess, I would say that @David's situation is a combination of the last two. The very high torque suggests a fatigue problem solved by ensuring that the load cycles stay within the non-fatigue domain and yet the connection must remain moveable. I don't know that for a fact, but I feel reasonably qualified to make that SWAG based on the location and components involved. I didn't work for Ford so I don't know that for certain.

I highly recommend a suitable torque wrench arrangement - either directly with a large enough torque wrench or with a torque multiplier of some sort, or with a force or weight measurement on a longer lever. The team has provided lots of very good suggestions on various ways of achieving the target torque.
 
At this point I'm going to investigate the minimally torque invasive potential problem areas, starting with the sway bar end links. :)
 
Most 1/2" drive torque wrenches don't go to more than 250 FtLb. You will need a 3/4" drive torque wrench to get 351 FtLb.
A torque multiplier tends to require a bit more rotation of the torque wrench so with the limited space you have to work that could be a problem. If the bolt is loose enough to make a clunking sound you can probably rotate the bolt with a 1/2" drive ratchet. if so the bolt and the shock absorber will likely need to be replaced.
My money is on the anti sway bar links being worn.
 
Of interest, I found this. It's for the drive system itself and doesn't reflect the maximum torque wrench size.

Screenshot_20250711_153159_Perplexity.jpg
 
David said:
I haven't noticed it in corners, only straight lines over bumps.
Click to expand...

Checking those bolts is free so nothing to loose, but I doubt that's it

Sounds like either ball joints or the shocks themself, I'm doubtfull that it is the sway bar links, the style that's in that truck (at least what rock auto says are in there) in my experience when they get slightly worn snap and you loose either the entire thing or 3 of the 4 bushings on the road, then they make no noise, and you don't really notice

That being said, if they are ok and you have to change the ball joints or shocks, change the links, the nut will likely shear off when you go to remove them when dropping the lower control arm anyhow, and I believe when I looked they were like 10$ each on rock auto

In any case, you have to jack that thing up and check stuff out, also note to check the ball joints with that style of suspension you have to jack up the control arm so the shocks are not putting tension on the ball joints as that will hide any play
 
Chicken lights said:
Really? My '08 F350 has ujoints in the front driveshaft. I just assumed the half tons were the same in that year
Click to expand...

Ford was probabaly the last to go to cv's in front on half tons, but that was still in the mid 90's, they went from that goofy articulating dana 44 to proper ifs with cv axles

Ford and Dodge both still run live axle front ends in 3/4t and up trucks, Chevy has had ifs with cv's since 88 in 1/2-1t trucks (with the exception of 3500hd 2wd with I beam axle in 88-98)
 
phaxtris said:
Ford was probabaly the last to go to cv's in front on half tons, but that was still in the mid 90's, they went from that goofy articulating dana 44 to proper ifs with cv axles

Ford and Dodge both still run live axle front ends in 3/4t and up trucks, Chevy has had ifs with cv's since 88 in 1/2-1t trucks (with the exception of 3500hd 2wd with I beam axle in 88-98)
Click to expand...
You're thinking axle shaft, when I'm saying driveshaft
 
Chicken lights said:
You're thinking axle shaft, when I'm saying driveshaft
Click to expand...

yes, sorry, since we were talking about the front end i assumed you were talking about axle u joints

2008 will have an automatic axle disconnect, that front driveshaft wont be turning unless he is in 4, and enough driveshaft u joint slop to have an audible clunk will come with pretty serious vibration
 
My checks on the internet come back with 351 ft-lbs for the lower bolt on the front strut/shock absorber of a 2008 F150. I’m surprised, it seems excessive, but that number reappeared on numerous sites. AND this is the bolt at the bottom of the strut, not just a simple bolt on a shock absorber. There’s a lot more going on, force wise, on the bottom of a strut than on the bottom bolt of a standard shock absorber.
I’d be calling Canadian Tire and other suppliers looking for a 3/4” torque wrench on loan/rent.. CDN Tire has a tool lending program. Not all tools, but a pretty broad range, and not at all,locations, so call around. Tool rental places could have one. Even a local garage might lend/rent one if you leave a suitable deposit.
 
phaxtris said:
yes, sorry, since we were talking about the front end i assumed you were talking about axle u joints

2008 will have an automatic axle disconnect, that front driveshaft wont be turning unless he is in 4, and enough driveshaft u joint slop to have an audible clunk will come with pretty serious vibration
Click to expand...
In 2WD (rear) on my S-10 Blazer there was a definite thunk when coasting downhill from the rear end: attributed to gear backlash/slop as this was an SUV/truck powertrain and not a passenger vehicle: never had any abnormal wear anywhere and after the FWD CV joint was replaced no problems (until I was T-boned 11 years later - I don’t recommend this).
 
ChazzC said:
In 2WD (rear) on my S-10 Blazer there was a definite thunk when coasting downhill from the rear end: attributed to gear backlash/slop as this was an SUV/truck powertrain and not a passenger vehicle: never had any abnormal wear anywhere and after the FWD CV joint was replaced no problems (until I was T-boned 11 years later - I don’t recommend this).
Click to expand...

a u joint clunk comes with serious vibrations, a clunk from excessive differential backlash wont, but i also think they fed you a line of sh!t about it being because the it was an s10 chassis (witch it is), it sounds more like that rear end was put together on a friday at 4 in the afternoon and maybe was at the extreme end of the spec for allowable backlash when it left the factory, and with some wear was probably out of spec, ive driven several s10's and s10 blazers, none had any audible clunk from the differential. That being said, excessive backlash on the diff of something low powered like a 4.3 s10 will likely not cause any catastrophic damage, im sure it would be a flintstone mobile and in the junkyard long before the diff let go
 
You must log in or register to reply here.
Back
Top