Scraping sound coming from trans or further back?

[cdoggwsu]

Some good stuff to think about here. At around 55mph the driveline does wobble a bit which I had originally assumed was due to the pinion angle, so hopefully the shackle flip will kill 2 birds with one stone.

Thanks again!

 

[NV_K5]

If it's your angle the shackle flip without any angle shim installations wil not make any difference. Also I'd probably put off the shackle flip until you figure out what is the actual cause of the noise. You get too many variables in there and it may take a long time to figure out what is the culprit.

 

[K5Greek]

im gonna say rear driveshaft angle also. ever since ive lifted mine i get the same grinding noise and im sure it has to do with the angle. get a shim in there and see if it helps.

 

[SUPER'BURB]

This may be to easy but..............

When I broke a motor mount it allowed my fan to contact the shrowd slightly. It sounded like a grind at the front of the rig and only happened when I was on the gas hard or twisted up a bit.

 

[cdoggwsu]

Yeah that's a good call. The first thing I checked was belts, pulleys and fan shroud to make sure it wasn't something ridiculously simple like that. I haven't had a chance to look at it in the last couple of days but I'll investigate the rear drive line as per the general consensus.

 

[70jimmy]

Instead of shimming the rear axle it isn't too expensive to buy new spring perches and cut the old ones off the axle and have the new ones welded on after the axle is rotated.

Pay somebody with a welder to come over, cut and grind the old ones off, smooth it and then put it together and rotated the axle so the yoke is pointing at the rear tcase output and tack the new perches on, then unhook and solid weld the new perches and put back together. Easy to do in a few hours.

 

[sawzall]

If it's your angle the shackle flip without any angle shim installations wil not make any difference. Also I'd probably put off the shackle flip until you figure out what is the actual cause of the noise. You get too many variables in there and it may take a long time to figure out what is the culprit.

I believe the shackle flip will change the angle via the rear portion of the spring being "lowered" by about 8 inches. right?

 

[cdoggwsu]

I believe the shackle flip will change the angle via the rear portion of the spring being "lowered" by about 8 inches. right?

Yeah, I was under the impression that regardless of the 'lift' the shackle flip provides, simply removing the 4" blocks would improve the pinion angle.

 

[cdoggwsu]

Well I finally started driving the truck again since the weather has gotten a little nicer. I took a trip out to a friend's place about 30 miles away and had a chance to do some testing on the drive. Not only does it make the scraping sound when I feather the gas pedal, it also can only be heard above 40 mph or so.

The other strange thing, if I push in the clutch at that speed it will make the scraping sound constantly until I drop below 35-40mph. Could this be the throwout bearing going bad? The scraping can be felt through the clutch pedal while its happening. I would think, however, that if it was the throwout bearing it would be heard anytime the clutch was pushed in...this is getting frustrating.

I haven't tested the driveshafts yet, so I guess that would be the next step.

Since it seems to be directly linked to the clutch, wouldn't that rule out wheel bearings and transfer case?

 

[rcamacho]

If you're that far into the hubs it's a good time to re-torque them anyway.

 

[cegusman]

My sm465 used to make that sound. ended up being the front input bearing was bad.

 

[cdoggwsu]

A little more testing today and the scraping can definitely be felt in the shifter as well. Opinions on rebuild kits? I suppose if I'm gonna get in there I should do the clutch as well. Anything else I should do while it's apart?

 

[Blue85]

I don't see why the a driveline angle issue wouldn't be felt through the shifter. So please don't pull the transmission until you've checked out the rear driveshaft. The way you describe the noise being dependant on the drivetrain load practically takes the front end out of the equation (unless the T-case isn't actually disengaging the front drive).

An angle finder is less than $10 at Home Depot. Go measure your driveshaft angles. If the angles in the two U-joints aren't really close, you've found your problem. The longer you run at incorrectly matched angles, the worse the U-joints will get. Checking and changing the driveline angles is just standard procedure with a lift kit. CK5 101 type stuff.



Also, somebody above recommended pointing your rear pinion at the T-case. Essentially the rear U-joint angle is 0. That is only for a C/V driveshaft. For a standard driveshaft, the U-joints should operate at the SAME angle (whatever it may be)

 

[bp71k5]

Are you sure it's not the wheel bearings? Having a tie-rod end that close to the wheel weights seems pretty suspiscious to me and sounds like loose bearings.

 

[cdoggwsu]

The way you describe the noise being dependant on the drivetrain load practically takes the front end out of the equation (unless the T-case isn't actually disengaging the front drive).

At this point I can fairly safely rule out everything from the tranny back. Front axle, wheel bearings, hubs...everything up front looks good. I guess I should update the threat title.

An angle finder is less than $10 at Home Depot. Go measure your driveshaft angles. If the angles in the two U-joints aren't really close, you've found your problem. The longer you run at incorrectly matched angles, the worse the U-joints will get. Checking and changing the driveline angles is just standard procedure with a lift kit. CK5 101 type stuff.

I understand the relationship between suspension lift and driveline angles...the PO did the lift so now I'm trying to find out what the problem is. I'll check the angles.

I have not ruled out the rear driveshaft, I know for a fact it's vibrating a little around 55mph, the only thing that's got me looking elsewhere is that the sound is definitely coming from the front of the tranny...it's way too far forward to be coming (directly) from the t-case. That isn't to say the cause isn't rooted somewhere else, that's just where I'm hearing it.

Aside from the vibration and wear on the ujoints, how could the driveline angle be causing a scraping sound at the front of the tranny?

Also, somebody above recommended pointing your rear pinion at the T-case. Essentially the rear U-joint angle is 0. That is only for a C/V driveshaft. For a standard driveshaft, the U-joints should operate at the SAME angle (whatever it may be)

The same angle, yes, but what is within range of allowable angle? I don't doubt that my rear angle is less than optimal, but I guess I'm just trying to understand why it would be causing the scraping sound that far forward.