Ubolts under torqued

thread from the dead, but here goes



the NEW specification is 44 foot lbs for those who get TSB 0008-14 done...

 

That's insane. Toyota still doing it wrong after all these years... 85 ft-lbs. on mine since they came loose after Toyota did the TSB leaf spring swap...

 

Now, now,,,, 44ftlbs is the new 37ftlbs....& yes, quite insane


But, what do I know....

 

37, 44, 73, 80, 85 and 90. I wish I knew what the real number was. I will check mine tomorrow and see what they are set at, but total confused as to what they should be?

 

Yup. 85lbs is what i have mine at too.

 

Lookie here:

http://www.autoandtrucksprings.com/pages/U-Bolt_Torque.html

^ Excellent reference IMO.

9/16 is about 14.3mm and they recommend 75 ft.lbs max for a grade 5 plated bolt, and they're talking about u-bolts for truck suspension. 100 ft.lbs for unplated 9/16 bolt.

If it helps you, I have had mine torqued to 85 ft.lbs for the last 4 years, they have never come loose or shown any problems. And I pack the shit out of my truck and camp and explore off-road as often as my schedule will allow.

 

very interesting post!!! I am not that great of a mechanic, and respect the opinions of many on this board & thank them for their knowledge, question? U-bolt? are these the same as what some call "Shackles"? I checked mine tonight, they are 19mm (3/4) & although I am not certain it would appear they are torqued at well over 100 ft lbs, I should mention I did have the leaf upgrade done!

 

Thanks Crom good info.

 

I'm no mechanic either, and I've learned a boat load here over the years... Here is one guys answer...

No. shakles are the part
that the rear eye of the leaf spring attaches to with a bolt and nut. The shackle itself is bolted to the shackle hanger, the shackle hanger is attached to the truck frame with big ass heavy duty rivets.

The u-bolts clamp the rear leaf spring to the spring perch on the top of the rear axle housing. The u-bolts use 19mm nuts and a piece of formed plate to grip and tension the axle housing.

Thanks to Doug for the thread and for raising awareness of this issue.

 

From what I heard, fine pitched threads (like the ones on our factory u-bolts) have a lower torque number than coarse pitched threads due to the thread surface area that makes contact. I was told that 37 or 44 ft lbs on a fine pitched thread is equivalent to a higher torque value on a coarse pitched thread.

 

Maybe I missed something along the way but Doug is referring to 19mm bolts??

Thanks for taking the time to explain, but I am confused as to which bolts are under torqued

 

It's actually Nuts not bolts. The U bolts are big U shaped bolts. Two on each side, going over the axle holding the leaf springs. There are 4 nuts on each side facing the ground.

 

Thanks, That is what I thought. I read ever post. but paid special attention to the OP 4WD, sorry about the "Nuts/bolts" mixup, Thanks again,

these are what I checked

 

the only thing I can figure with the spec being loose is that for crash rating and energy absorbing...the u-bolts are set looser than the standard 80+ so that in a crash the assembly can slide and bust the pins or something to allow the rear end to crunch up better ? otherwise it really doesn't make sense for them to be so loose. anyhow i am gonna keep mine at 44 (the TSB spec) and it they start to loosen by themselves, will red/blue loctite them

 

The confusion was mine. 19mm is correct!

 

To each his own. However, you could place a few local calls to some respectable auto mechanics shops and ask them what they do. Tell them about the 44 ft.lb spec. See what they say.

I know I mentioned it before but mine were set to 37 or whatever the dealer put them at after my TSB leafs were installed, and they in fact came loose with normal city driving. Very loose actually on both sides, a couple of the nuts almost completely backed off all the threads.

FYI In 2009 Toyota redesigned the frame with improvements for crash testing. I've read the technical doc on the changes and it did not mention anything regarding the rear axle housing.

 

Dude, every time I see you post, all I can think of is Arnold Schwarzenegger as Conan, yelling "CROM!"

Sorry, off-topic, carry on. Mine are still at 73 and holding fine.

 

look, you ask me to talk to spring shops and mechanics fresh out of the womb or one foot in the grave all you want. Toyota knows what it is doing believe it or not, and there is some actual engineering reason for that spec. what the engineering decision is based upon who knows. tacomas once had a problem with cracked springs. customer report harsh rides. crash data maybe shows looser ubolts allow the bed/frame to crunch up better in a crash I do not know. maybe it prevents gas tank from splitting open if the springs can bust off easier who knows ?

But I know enough to say...that is the spec and Toyota put it there for a reason...especially since, for years (a few anyway according to what I find on these forums) everyone and their mom is contacting toyota and sayin Hey that 37 spec is incorrect...and each day I go back to techinfo.toyota.com the spec is just as it was written....tight tight tight for gen1, and suddenly gen2 BOOM, 37. if it was wrong they'd have corrected the docs by now...

yes crank them down to 80 or 90 it won't cause any issues except tighter bolts and a tiny tiny bit stiffer ride. really there is not a problem.

WHEN toyota actually goes and makes the change to a tighter spec then I might listen to anyone else, but until then....it's just noise and speculation and 'well it is what we've always been doing since the spring suspension been invented back on wagon train days'.

the spec is correct for 'reasons not clear' and it is 37...if you get the new leafs from TSB 0008-14 then the spec is increased to 44. still low. but changed.

some one PLEASE provide proof that Toyota states the spec at 37 or 44 is incorrect and the real spec should be XYZ. besides what suspension and leaf spring experts say, I want to see Toyota Motor Corporation boost the spec or say 'it a mistake' (TSB 0008-14 excluded, that is 44) I agree 100% it is odd and normal would be 80+...but I also assume there is a specific reason


my whole point is the last ASE training I ever saw didn't say 'tighten u-bolts to Joes recommendations or what that other guy said recommendations'...it said 'tighten to manufacturers recommendations'

 

That's a helpful chart!

I can tell you when I did the lift on my 2013 (non-tsb) last weekend, man, those u-bolts were not on tight, at all. I bet the 35 range...

I torqued the new ones to the Haynes/Land Cruiser spec, which IIRC was 65. I'll recheck in a tank of gas.

 

2014 DCSB 4x4, bought in Dec 2013. Checked this am, drivers side was at 55 and passenger side was at 65. Took them to 73. Will check them in a week or so.