Safe? Unsafe? common practice? sounds stupid

[n8thgr8]

I KNOW I'm going to get ripped on for this, but there is sort of a serious question in here somewhere...
So I'm experiencing some noise under the ol' truck, but I can only hear it when I'm driving 30+ mph.
The only thing I can think of is putting all 4 axels up on stands, removing the wheels (you know, for safety!), and laying under the truck to help diagnose this as a buddy is in the car...
Maybe it's just the common sense in me, but this just sounds ridiculously unsafe and goes against my better judgment as a reasonably intelligent human being. :ack:
Please tell me that this is in the same category as driving with a friend under the hood, or strapping someone underneath.
What do you guys do to diagnose those mystery sounds underneath that show up when you're driving?

 

[n8thgr8]

Oh crap, it posted twice. It's bad enough once!

 

[rovercanus]

I like the idea of strapping someone under the truck. Got any kids?

 

[MUSKYMAN]

yeah I wouldent do that, it wont really give you any information.

first off you wont be recreating the same forces that driving down the road does so the experiment is really just a waste of time.

start over and describe what you hear and when.

does it make the noise when under load?

on throttle or coasting?

does it still make it if you step on the brake ?

yada yada yada...

see we can help you by starting at scratch.

what is the sound?

 

[MUSKYMAN]

I like the idea of strapping someone under the truck. Got any kids?

I have hung out the door of alot of cars listening to sounds:smilelol:

 

[rovercanus]

I have hung out the door of alot of cars listening to sounds:smilelol:

Yup, with someone holding onto your belt so you don't fall out.

 

[stu454]

That's why my belts are horsehide

 

[ptschram]

I don't even feel comfortable with them on the lift and everything cribbed up.

 

[mapman97]

If you have to ask.

Although, that visual would probably make Letterman or Leno.

 

[dirtyjim]

i know several people who have put the trucks on stands to try & find sounds & none of them were hurt but i sure as hell wouldn't crawl under their trucks.
the only way i would even consider doing it would be if had been drinking heavily and both the axles & the body had jack stands & both the axles & the body was straped down where they couldn't move.

 

[GregH]

This should help:

http://www.walmart.com/catalog/product.do?product_id=10710724&findingMethod=rr

Please take pics.

 

[n8thgr8]

WHEW! Glad to hear a little confirmation that it's a bad idea.
The noise...
It's coming from underneath, mid truck in the center area.
It's a clacking that doesn't happen until I reach 35 mph or so, then will happen the rest of the day, no matter what the speed. Even creeping along. The speed of the clacking seems to be dependant on speed too. When I'm creeping along, it creeps along, when I"m going faster so does the sound.
It seems to happen more during deceleration, or coasting than under load. Although it seems to be getting worse, and will happen just about anytime now.
Any ideas?

 

[jymmiejamz]

I don't even feel comfortable with them on the lift and everything cribbed up.

X2! I get nervous every time I see that going on in the shop.

 

[I HATE PONIES]

U-Joint? Test by removing 1 driveshaft at a time.

 

[n8thgr8]

So moving drive shafts one at a time, Up on the stands, and move by hand? I'm beginning to suspect a u joint too.

 

[I HATE PONIES]

So moving drive shafts one at a time, Up on the stands, and move by hand? I'm beginning to suspect a u joint too.

No. Take one shaft off and lock the cdl and then drive the truck. No change = replace the first shaft and then take the other shaft off and drive the truck.

 

[ptschram]

So moving drive shafts one at a time, Up on the stands, and move by hand? I'm beginning to suspect a u joint too.

Put it up on stands, grab the driveshfts. Pretty much any detectable play is too much.
You might be surprised to find out how worn one of them is.

 

[n8thgr8]

AH! Got it! I'll try that this afternoon.
Much appreciated all, I'll keep you posted...

 

[MUSKYMAN]

what year D1 is it?

do you have a rear rotoflex or a rear ujoint.

the easiest way to find a bad u-joint is with all 4 tires on the ground.

with the truck turned off in park lay under the truck and have someone rock the the truck forward and back against the resistance of the trans in park.

as the truck rocks the driveshafts will load and unload and a bad u-joint will clearly show slack in it as the yokes wind up and unwind as they load and unload.

you can also just lay there on your back and put your foot on one of the tires and get it rocking by yourself . Once you get onto this method you can xcheck the u-joints in about 1min.

 

[maxyedor]

I've seen trucks, cars, buggies, etc running on jack-stands so many times it's rediculous. Would I be afraid to do it on flat level ground with good jack-stands, no, will it help track down your sound, not really.