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How to measure high torque values?

David

David

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My new-ish to me 2008 F150 has a clunk in the front end that have narrowed down to a few possible causes. One is insufficient torque on the lower shock mounting fasteners.
The factory manual specs 351 ft/lbs on the lower mount.
I have a pneumatic 1/2" impact gun but I have no idea what it's capable of putting out and I don't want to risk shearing the bolt.
How do I measure such a high torque value?
1752166413339.png
 
Unless you buy another torque wrench with the larger range, your best bet may be a torque multiplier.
Personally I'd just put a cheater on the socket handle, pull till it strips , and then back off half a turn.
 
I would suggest getting/borrowing a torque wrench (click or digital) that can handle 350+ ft-lbs. I don’t rely on impact drivers (either 1/4” hex or 1/2” square drive) for accurate torque unless I’m using a torque limiting extension bar (and they typically only go up to 150 ft-lbs in 10 ft-lb. increments).

Assembly Line powered torque drives are “computer controlled” and record the actual torque applied.

Edit: @Doggggboy beat me to it.
 
David said:
My new-ish to me 2008 F150 has a clunk in the front end that have narrowed down to a few possible causes. One is insufficient torque on the lower shock mounting fasteners.
The factory manual specs 351 ft/lbs on the lower mount.
I have a pneumatic 1/2" impact gun but I have no idea what it's capable of putting out and I don't want to risk shearing the bolt.
How do I measure such a high torque value?
View attachment 67050
Click to expand...

I had one of those front end "clunk" noises with our 2009 Chevy Uplander. Drive me around the bend trying to find it. I could make it "clunk" by rocking it forwards and backwards by hand. Turned out to be lower motor mount needed tightening.
 
My suggestion is to use the torque wrench that you have, and then 'feel' how much it takes for some force level in the range of that wrench. Then add a cheater bar of a specific length, and 'feel' that much as you turn it again. Torque increses linearly with distance, so the math is simple
 
If you need a torque wrench Parts Source has the loan a tool program. The largest torque wrench on the website to loan is a 1/2" drive that goes up to 250 ft/lbs.
 
David said:
My new-ish to me 2008 F150 has a clunk in the front end that have narrowed down to a few possible causes. One is insufficient torque on the lower shock mounting fasteners.
The factory manual specs 351 ft/lbs on the lower mount.
I have a pneumatic 1/2" impact gun but I have no idea what it's capable of putting out and I don't want to risk shearing the bolt.
How do I measure such a high torque value?
View attachment 67050
Click to expand...
That doesn't seem right.... I'm not saying I don't believe the factory specs but my wheel nuts on the big horse are 450-500 ft lbs. 351 for a shock mount for an F150 is... odd

You're welcome to borrow my 3/4" torque wrench to check your nuts
 
I like @mbond's approach. It can be improved using a weight scale. All torques are just force at a distance. The math is easy peasy.

PLEASE DO NOT USE AN IMPACT WRENCH!! I'll have a heart attack over here.

Or, you can buy a really nice torque wrench for $150 on Amazon and use it for other jobs too. I have this exact model for my farm equipment. It works GREAT! I've even checked it and found it to be well within spec.

 
high torque specs for through bolts thats for sure, i would be be looking more at your ball joints or sway bar links, that normally where you get the clunks from....if you checked your ball joints did you check them correctly, and with a prybar as well, or just the ol tire wiggle ?

3/4 drive torque wrenches normally get up into the 350-400ft lb range, but it takes quite a bit to get it to break up there, have fun backing it up, its going to turn with probably 200ftlbs of force on the other end (the bushing, friction of the head on the mounting tab will all eat up some of the 350 the nut side wants)

i doubt any dealer mechanic has pulled out a torque wrench replacing any of those bolts, i would put money on 5 seconds worth of ugga duggas on an air impact is the standard procedure
 
phaxtris said:
high torque specs for through bolts thats for sure, i would be be looking more at your ball joints or sway bar links, that normally where you get the clunks from....if you checked your ball joints did you check them correctly, and with a prybar as well, or just the ol tire wiggle ?

3/4 drive torque wrenches normally get up into the 350-400ft lb range, but it takes quite a bit to get it to break up there, have fun backing it up, its going to turn with probably 200ftlbs of force on the other end (the bushing, friction of the head on the mounting tab will all eat up some of the 350 the nut side wants)

i doubt any dealer mechanic has pulled out a torque wrench replacing any of those bolts, i would put money on 5 seconds worth of ugga duggas on an air impact is the standard procedure
Click to expand...
I'm going to start with the sway bar links as I have also read that they are subject to wear. On the 04-08 F150's they look like six inch long tie rods. A split in one of the four boots and pretty soon it's all over.
 
Chicken lights said:
That doesn't seem right.... I'm not saying I don't believe the factory specs but my wheel nuts on the big horse are 450-500 ft lbs. 351 for a shock mount for an F150 is... odd

You're welcome to borrow my 3/4" torque wrench to check your nuts
Click to expand...
It does seem really high to me too. Never torqued anything that tight.
 
David said:
It does seem really high to me too. Never torqued anything that tight.
Click to expand...

What size is the bolt? Unless it's something like M16 or bigger and Grade 10, I might question if they put the wrong numbers in. Like using the Nm numbers as the lb-ft and then did a conversion from that higher lb-ft into the Nm. Ie the guy was like "ya, needs to be torqued to 350...what's that in Nm? oh ya, 475".
 
SomeGuy said:
What size is the bolt? Unless it's something like M16 or bigger and Grade 10, I might question if they put the wrong numbers in. Like using the Nm numbers as the lb-ft and then did a conversion from that higher lb-ft into the Nm. Ie the guy was like "ya, needs to be torqued to 350...what's that in Nm? oh ya, 475".
Click to expand...
No idea as I haven't ventured underneath to have a look. I'm going to double check the specs.
 
David said:
No idea as I haven't ventured underneath to have a look. I'm going to double check the specs.
Click to expand...

For what it's worth I have read some conversations on Ford forums regarding the high torque on those bolts when replacing the shocks/struts.

For example:
Ford F150 Forum

And:
Ford F150 Forum

Based on those discussions I think the torque spec. is accurate.

Edit - Here's another site where someone posted all kinds of torque specs for 2004-2008 F150's:

Suspension Torque Specs

The images are a little small but if you hoover the cursor over the parts it brings up the specs.
 
You could use a torque multiplier. We use them to tighten the bolts that hold the wings on airplanes. I don't know if they can be used on a torque as low as you want though.
 
David said:
I'm going to start with the sway bar links as I have also read that they are subject to wear. On the 04-08 F150's they look like six inch long tie rods. A split in one of the four boots and pretty soon it's all over.
Click to expand...

It's all subject to wear, ball joints, shocks, sway bar end links live a hard life

I looked it up Sway bar links in that are the simple bolt/bushing type, in my experience they just break and fall out on the road some where, I would be looking hard at the ball joints for your clunk.

You could also throw the parts cannon at it, truck is 17 years old, probably in need of some love.....big ol rock auto order shouldnt be to expensive
 
If you can get a 3 ft bar on it, use a digital scale at the 3 ft mark from the bolt and pull it with 117 lb force. Better if you can get a 4 ft bar on it, 88 lb pull force. Digital scales are cheap on Amazon or maybe you or a friend has one.
 
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