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Why is my front driveline hitting the crossmember?

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safooma

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Hello all. This is my first post here, and I seached for the answer like crazy and couldn't find anything, so don't hurt me /forums/images/graemlins/grin.gif

OK, I installed a 2" add-a-leaf to my truck(front only) and everything was great--or so I thought. The truck is a 74 chevy 3/4 ton 4x4. I took it out for it's first wheeling trip since the add-a-leaf install a few weeks ago and noticed that when the hubs where locked, it made a LOUD banging sound from under the floor. I unlocked the hubs and the sound went away. A week later while hauling my camper, I noticed sounds coming out of the front wheels--in two wheel drive. I swapped out the front wheel bearings and they were toast, so I figured that that was the problem--and it was, at least while free wheeling in 2 wheel drive. Thinking all was well with the world, I took the truck out to the mud last weekend and it made same loud whacking noise when the hubs where locked. It sounded like somebody was beating on the floor with a hammer from underneath. So I ventured underneath the beast again today and I think I found the problem:

The Cardan CV on the front driveline is contacting the crossmember/support as it rotates. I couldn't believe it. To verify, I pulled the driveline and took it for a drive hubs locked and sure enough, the sound is gone. Here is a pic of the cardan where it hits the support:

cardan_cv.JPG


I should mention that the truck has always made the noise when the hubs are locked, just not as nearly as consistently or as pronounced as now. It used to only do it rarely(probably only when the front suspension maxed out, now that I know where the sound is coming from), but since it so rarely did it, and only while off roading, I was never able to nail down the cause. I'm sure that it was the lift is what is making it do it all the time, but I also know that there are TONS of trucks like mine that are lifted and do not have this problem.

Has anyone ever seen this before? Shouldn't the tcase be higher or the support lower? I had noticed before I had installed the lift kit that the floor/body above the tcase had been cut out, and a new piece screwed in over the cut, in what looks like an attempt to give the tcase more headroom. Here's a pic of what I am talking about, with the area highlighted in red(fear my PS skills):

np_203a.JPG



So what do you all think? Where should I start? Replace the bushings in the support mounts maybe? Or is it just monkey rigged in the first place?

Any help would be greatly appreciated.

Thanks!
 
is the crossmember bent? i would start by replacing the mounts

my dads blazer did the same thing, the cross member looked like it hit something and bent it back and up pushing it into the CV joint.
 
My front DS did the same thing. I used a propane torch and heated were it was hitting. Then once it was hot, I use a 6 lb. sledge and flated the x-member alittle. You don't need much room. I gave it about an 1 1/2 inches to move.
Hope this helps
 
Perhaps you should replace the mounts . Looking at the rear view , I can see the drivers side mount is squished down some. Maybe they are worn enough to lose some clearance, not much but enough to rub . /forums/images/graemlins/thinking.gif
 
I'd start by replacing the worn out tcase mount. Looks like the tcase is hanging lower than it should.
 
I third the mount replacement first. See if it rubs after that. Then you can either space the T-case up, or massage the x-member out of the way.

mine does this as well after I switched to a flat x-member from the W shaped one. It contacts in a very small patch so I am just gonna cut a small hole there.

Either way let us know, and welcome to CK5 /forums/images/graemlins/peace.gif /forums/images/graemlins/waytogo.gif
 
The same thing happened on mine and replacing the mounts fixed it for me.... the other thing you may need to do is prop the t-case some..... when that joint is moved to much it can make it cause problems.... The other thing is change the front u-joint... they wear a grove as time goes by, when you change the angle on the driveshaft it starts a new grove which can make the u-joint to fail......
 
Thanks for all the replies. I am rebuilding the cardan and replacing the tcase/tranny mounts and front u-joint this weekend. I hope that fixes it, I have yet to go throw any mud around since I got my new tires, so I am definately crossing my fingers. My only concern is that there is only about 1/2" of clearance above the tcase as it is now--I can barely fit my pinky finger between the top of the tcase and the tunnel. That's not much room to work with.

Did anyone have any input on the giant cut-out above the tcase? Is that a normal thing, or was that done by a monkey with a saws-all?

Thanks again!
 
[ QUOTE ]
Did anyone have any input on the giant cut-out above the tcase? Is that a normal thing, or was that done by a monkey with a saws-all?

[/ QUOTE ]

Looks like you live in the rust belt... Maybe someone replaced the cab with a 2wd cab? Then cut out the floor to patch in a 4x4 floor?
 
So I swapped out the tcase mounts and it's fixed. Took it for a test drive around the block and over some curbs with the hubs locked and not a sound. Yes! Can't wait to take it our for a test. Thanks for all of the replys and help!

Finished product:

fixed1.jpg


fixed2.jpg


fixed3.jpg


And two if the truck itself, so you know what you have been helping me with:

right_tree.jpg


front.jpg
 
Glad you got it worked out. Mine looked alot worse than yours did, like a black marshmallow /forums/images/graemlins/rotfl.gif
 
Did you get your T-case mounts at the parts store? If so, how much? Thanks.
 
[ QUOTE ]
Did you get your T-case mounts at the parts store? If so, how much? Thanks.

[/ QUOTE ]

I got them at a local knechts. Each mount consisted of a top and a bottom. The top halves were $7.xx and the bottoms were $4.xx. The whole thing cost less than $30, including some liquid wrench and some new shop towels. Taking them off was easy, but putting them on wasn't nearly as easy. The holes would not line up, so I had to make the holes in the mounts themselves a little bigger so that I could line everything up.
 
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