U Bolts Torque Value

The previous air bag was only a year old and the plastic base broke apart.

I didn’t see how the previous air bag looked before it broke.

Once the new one was installed, that’s when I noticed the bar the bag sits on is not in the right position.

I’m assuming that’s what broke the plastic base.

So I got a Firestone one with the metal base.

The truck is driven by a fairly new driver that still has a lot to learn for how things work and what to look for.

So tomorrow, I’ll take the suspension apart, clean everything up, inspect, find the cause. Go from there.

 

I had a torque chart made by Triangle Spring that I got from my spring shop some 20 years ago and I believe the 7/8 bolts were 450-500 just like the wheel studs on trucks. That has always made it easier for me to remember. I just set em at 500 and than recheck torque after a few days.

 

I believe the 46k lb version of the Airliner goes to either 550 or 600 ft-lbs. Been over a decade since I last did one. Seem to remember it being everything the shop 3/4 drive torque wrench had. Never touched the 40k lb version of the Airliner. Don't know if the u-bolts are the same or not though.

 

We have both the 40,000 and 46,000 lb airliners here.

The 40,000 version is 3/4 in u-bolts and the 46,000 is a 1 inch.

I just measured both with the vernier caliper.

Also the 40,000 has no brace plate (I think, no idea what that part is called) that goes across between the 2 air bags like the 46,000 has.

 

Freightliner has maintenance and operator manuals on line for free to view. Those u-bolts tend to stretch with time because they carry weight, bad design in my opinion.

 

Some of the 46k versions lack the plate between the 2 springs as well I believe.

 

Freightliner has 2 style trailing springs. Make sure you have the correct air bag. One is a straight spring, the other turns in under the frame.

 

Worked on the freightliner suspension today.

Once the U-bolts were loosened, the spring moved over and the air bag straightened out on its own.

So it may have wiggled over towards the differential over time.

The spring is still not perfect once everything is back together.

All 3 other springs hold the bags near level while this one right now is slightly crooked but a lot better than before.

Eventually we will change out that spring.

For now, it’s not bad looking at all.