Noise when 4WD engaged

[1985K20]

Just went to try the 4WD on my truck this morning on the beach, and now i can hear a grinding kinda noise when heavy load applied to front drivetrain.

If i drive normal,it wont happen or almost never but when i gave her 3/4- full throttle in 4LO it will make that scary grindind noise coming from front end

In 4HI it's little better t'ill i floor it. Must be cause more torque gettin there in 4LO...

Here's the front end known condition: new ball joints, new u-joints(hub ones),
little bit of slack between yoke and u-joint, and for the rest I donno; never got the front cover off yet.

So if any of you guys ever went thru somethin similar: could ya give me an idea what to look at or to fix???

 

[big jimmy 91]

Other Things

Check your motor and body mounts
I had bad body mounts that let the fan eat my shroud , which then rubbed a hole in the rad core
Just something to look at other than the drive train

BTW it only happened while off road and I twisted the truck out of shape , good luck.

 

[1985K20]

I just remember i seen loose cross member(t. case) bolts last time i was under the truck...This could be my problem would not it???

 

[bigbadchev84]

check the front driveline u-joints and also the c/v joint up by the transfer case, my buddy was up wheelin with us last weekend with a bad c/v, it was enough to make u cringe when he got on it. it did finally blow apart.

 

[1985K20]

Ok I think i might have found the problem this time...I got mad tonite and i start taking parts off my front end

I got front driveshaft off, inspected it + u-joints and c/v: Everything looks allright; front u-joint's fair, split shaft union's splines look good, and c/v joint looks good also

So i kept inspecting t.case: I need a yoke seal(front)+ front diff. yoke seal also I checked t.case bolts to tranny: nice and tight.(Big blocks like to loosen them)

I was still with no answer So i grabbed my t. case tailshaft with both hands and reefed on it and guess wha?? I lifted the whole drivetrain from a good 3 to 4 inches The diagnostic: worn out t.case mount+ broken bolt(mount)

 

[1985K20]

Yep 99% sure that the grinding/rubbing noise was caused by broken t.case mount.

Put new mount on and i cant hear that noise no more.

I think when heavy torque was created by motor,the left side of drivetrain was goin up, allowing c/v joint to rub on cross member...or something like that