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Front Strut, 777F truck

El Nugget

Member
Joined
Dec 23, 2015
Messages
5
Location
Planet Earth, mostly.
Has anyone seen a crack like this before on a Cat 77F front cylinder suspension strut.
I have a sneaking suspicion that the truck drivers may be trying to "wheelie" the truck when dumping a load.
77F front strut.jpg
strut mounting.jpg
 

El Nugget

Member
Joined
Dec 23, 2015
Messages
5
Location
Planet Earth, mostly.
It is cracked right where the taper part of the strut marries to the spindle housing. We are trying to determine if there was too much oil in the strut, if there was an overcharging of the gas, to cause the suspension to extend rapidly.
I don't think that this is the case as the guys have done this job many times. Our road conditions are pretty average so I am leaning toward a Wheelie situation or too fast over big bumps in the terrain.
 

Nige

Senior Member
Joined
Jun 22, 2011
Messages
29,317
Location
G..G..G..Granville.........!! Fetch your cloth.
From your reply it looks to me as though bottom of the strut housing (where the wiper seal fits) has been impacting the spindle, at least that's what the photo seems to indicate. If I had to bet I'd have said the strut had too little oil in it rather than too much. The oil quantity controls the damping rate, the nitrogen gas pressure the initial ride height either loaded or empty. Reduced Damping will permit the strut to both bottom and top out on anything less than a billiard table, especially loaded.

Another question. Does it have a payload system installed and do you use the numbers..? If so is this truck averaging maybe 5-10% less payload than the other trucks in your fleet..? I'm assuming you have more than one truck.

Our road conditions are pretty average so I am leaning toward a Wheelie situation or too fast over big bumps in the terrain.
You don't have average roads if your trucks can wheelie, more like poor or very poor by the standards I'm used to.
 
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