Front end dive

[henry davis]

Hey guys,

I did a little test drive of the GMC last night to check the security of
some of my installations. When I applied the brakes firmly with a quick
release of the pedal, I noticed a definite "dive" in the front end with a
more pronounced dive on the passenger side. I don't recall having the
differential to the right before but may have. Before I start going through
the front end again, anybody have any ideas about what could be the problem
or is it normal?

Henry

Henry Davis Consulting, Inc / new product consulting
PO Box 1270 / product readiness reviews
Soquel, Ca 95073 / IP reviews
ph: (831) 462-5199 / full service marketing
fax: (831) 462-5198
http://www.henry-davis.com

 

[henry davis]

>Henry,
>
>Did you do these stops with your hands off the wheel?

No, hands were on.

>Is it possible that a torsion bar could be fatigued?

POssible. I'm going to get out the brake cleaner and go after the torsion
bar looking for cracks and/or wear.

>Tire pressure?

Looks fine.

>How about all those batteries on the passenger side?

I only have the engine there now. Golf cart batts come later. AFTER I find
this problem.

>No answers, just guesses.
Thanks for the input.

Henry

 

[henry davis]

Thanks for all the input. Checked the torsion bars, bushings, etc. All
seemed fine. So I thought that I'd try the check the shocks. But first,
before I started taking things apart, I got my wife to stand on the front
bumper and jump up and down to get some resonance going. Voila! The problem
was revealed. The passenger side shock was moving up and down inside the
upper mount. It *looked* tight. It felt tight. So I grabbed the torque
wrench and checked the torque. Oops! Although the nut was on the bolt
plenty far, it seems like when the shocks were installed a longer bolt was
used on the passenger side. So, plenty of bolt would protrude beyond the
end of the nut. Tightened to 90ft-lbs and the movement went away
completely. Driver's side was torqued to about 70 ft-lbs. Now when I bounce
on the bumper I get very little movement. Irene barely budges the thing. I
had planned to recheck torque in the front end and rear suspension out of
paranoia anyway. It's interesting to see how much difference a relatively
small amount of play makes in the front end.

Henry

 

[emerystora]

> I got my wife to stand on the front bumper and jump up and down to
>get some resonance going.
>Henry
>

Henry - you didn't say how fast you were going when you got Irene to
do this. Hope you kept it under 65.

Emery

 

[henry davis]

>> I got my wife to stand on the front bumper and jump up and down to get
>> some resonance going.
>>Henry
>
>Henry - you didn't say how fast you were going when you got Irene to do
>this. Hope you kept it under 65.
>
>Emery

You bet! we were blazing along at a whopping standstill. It was very
interesting to see how the resonance changed as I tightened things up.
Irene could get about 3-4 inches of movement at the bumper by timing it
right. As she said, she got her exercise for the day, but she didn't want
to stick her head into the wheel well while I bounced the coach! I offered.

FWIW, approximately 0.25" of movement at the upper shock mount and a
minuscule amount at the lower mount were enough to let the bumper move 3-4
inches. Now it's tough to move it an inch.

Henry

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