Cracking Cross Member

[Hunter013]

2020 Kenworth T800 quad axle dump truck

I noticed a cracked cross member while I was last under my truck. Its the carrier bearing cross member. Ill post pictures. I am waiting on a new one to get delivered and I was curious what would cause this cracking? I believe the piece is aluminum and I know the driver is not the most gentle driver I have. On the cross member closer to the motor, the bolts that connect the gussets to the cross member were loose. Would that cause play in the frame and crack the other cross member?

 

[Hunter013]

 

[funwithfuel]

I'd be looking at the u-joints and carrier bearing. Make sure some jack-wagon hasn't hung the shaft out of phase. That looks like stress directly inline with the mounting of the carrier. I would guess someone tweaked or uninstalled something during a clutch service or something along those lines. That's definitely a symptom of something bigger.

 

[Hunter013]

We’ve had this truck since new and we’ve never touched anything in the driveline. I’ll check u-joints, slip joints, carrier bearing and phase of drive shafts.

 

[Coaldust]

As someone who watches a fleet of late model T800\T880’s, it’s not uncommon to find cracked crossmembers. They just appear to crack with no rhythm or reason. Especially the one between the axles.

 

[funwithfuel]

Really, the only time I saw aluminum crack like that was an imbalance. But , I've been away from trucks for 20+ years. I remember a customer with an aluminum frame freightliner. The corrosion at the crossmember gussets would split the frame rails. Not a good choice for the midwest, fer sure.

 

[Coaldust]

Stamped steel. I forgot to mention I’m dealing with straight trucks. I don’t hear or see much about tractors breaking crossmenbers.

 

[funwithfuel]

Well, the bright side is, no huck bolts. Looks like all traditional bolts, washers and crown locks. I would personally opt for flanged frame screws with flanged crown lock nuts. But that's just me and my preference. You might also consider, the driveline angle. I don't remember the magic numbers, I think it's 3° but I can't say for sure. Maybe the carrier needs to be raised or lowered.

 

[56wrench]

That slotted open hole in the crossmember causes a stress point. On a truck that goes off-highway its a crack waiting for a time to happen. A poor place for an open hole in my opinion

 

[Acoals]

They just appear to crack with no rhythm or reason.

* Raises hand * Teacher, could the cause be in the red circle?

 

[Truck Shop]

Mexico--China or made in the USA has nothing to do with it---KW has been building
those same crossmembers and gussets going back to mid 60's. Cracking has always
been a issue. Bolts getting loose has always been a issue-puny 10mm on late trucks.
Pete can have the same problem.

 

[funwithfuel]

The biggest problem I remember with KW was those elephant ear trunions. They would always tear by the bushing for the track bar. First, stamped steel then cast pot metal. Don't know if they ever came up with a fix.

 

[Truck Shop]

Don't know if they ever came up with a fix.

Never did--KW doesn't even make that series anymore and some of their older suspension
is aftermarket or salvage for parts. Pete is the same way.