Grinding sound post gear install

[jfz80]

Or you could just shift into low remove the fuse and put it back in high to test. Well documented on here. But slee will have your CDL button.

 

[Jeff Elliott]

thanks @jfz80 - is it as simple as that? And do you mean the 30 am fuse in the panel below the steering wheel?

If so I will give that a try!

 

[jfz80]

Hey Jeff. Sorry bout that. Did not get a notification but im traveling and away from the 80 and fsm. Someone should
Chime in to verify but idea is shift to low, let cdl lock, remove fuse (for cdl operation) and shift back to high range. Id need to look to ID which One.

 

[Jeff Elliott]

UPDATE: dropped the front shaft, shifted to low and pulled fuse, back in high and went for drive. No more bad sound that I can appreciate.

I do have a wooommmpp, woooommmp at a certain speed so I plan to rotate the yoke on the rear by 180 degrees and test again - it's possible both shafts were put back together 180 degrees off. Once I determine the back is all set I will retry the front and report back. I may have to rotate the front yoke 180 as well. More to come.

PSA - don't try to drop the rear yoke immediately after a test drive... I have it on good authority that you can burn the hide right off your knuckles on that hot muffler.

 

[Teebo]

Thanks for the update. Let us know what you find.
I'm rebuilding a set of locker axles to put under my 92' and anticipate similar problems since I can't exactly mark the shaft placement when I'm replacing the axles.

 

[Box Rocket]

UPDATE: dropped the front shaft, shifted to low and pulled fuse, back in high and went for drive. No more bad sound that I can appreciate.

I do have a wooommmpp, woooommmp at a certain speed so I plan to rotate the yoke on the rear by 180 degrees and test again - it's possible both shafts were put back together 180 degrees off. Once I determine the back is all set I will retry the front and report back. I may have to rotate the front yoke 180 as well. More to come.

PSA - don't try to drop the rear yoke immediately after a test drive... I have it on good authority that you can burn the hide right off your knuckles on that hot muffler.

if the driveshaft yokes are out of phase, rotating 180* may not correct it since that rotation could still be out of phase. Lots of info on how to get the driveshaft yokes "in phase" so rather than just doing an arbitrary rotation, just make sure they are in phase and you'll be good.

 

[Box Rocket]

back to the original question. I chased a similar noise after installing my 4.88's. Took a long time and no less that 3x pulling the diffs but finally ruled out the diff setup as an issue. Driveshafts were all checked and ruled out, as was spindle bushings. I still get some noise on decel and I'm relatively certain that it's an output bearing on the tcase. I have a spare case that I'm planning to install new low range gears into and swap that in so I'll address bearings during the tcase rebuild.

You might check the tcase output bearing.

 

[Etxmike]

Im chasing down noise on decel and my tcase is 100% rebuilt. Im currently waiting on rear arms and if that doesnt work im going to get a dc rear shaft

 

[Jeff Elliott]

Update #2. Rotated the yoke 180 and my wooommmp.... wooommmppp is 99% gone. Based on this, I'm going to conclude I had it "180 degrees out of phase" meaning it was technically in phase but out of balance.

Now I need to reinstall the front shaft and see how we do - I'm guessing it's out of balance (meaning 180 degrees out of phase) as the grinding noise went away as soon as I eliminated it.

 

[Jeff Elliott]

Also, one of my studs in the transfer case flange is spinning... do I have to replace it or could I just tack weld it?

 

[Jeff Elliott]

And, while we're talking about shaft angles, etc., here's what I measured on my rig (though I'm not sure I did it correctly - would appreciate any guidance).

Frame angle = .5 degrees
Front output flange of xfer case = 87.6
Front 3rd member flange = 83.5
Angle across bearing cap on top of knuckle = 3.5

Any thoughts?

 

[Box Rocket]

Driveshaft flange angles should be parallel if you have single ujoints at each end. Vibes will increase (and possible have joint binding) the farther from parallel the flanges are. IF you have a double cardon joint in either driveshaft, the DC joint should be at the Tcase end and the diff flange should be pointed directly at the tcase. In other words the pinion shaft should be directly in line with the driveshaft.

Based on your numbers you probably have some vibration in the front driveshaft because of the difference in angle although it's probably minimal. It could get worse on decel when there's no load on the shaft.

 

[Jeff Elliott]

Based on your numbers you probably have some vibration in the front driveshaft because of the difference in angle although it's probably minimal. It could get worse on decel when there's no load on the shaft.

UPDATE #3: Box rocket called it... I reinstalled the front DS, flipped the yoke 180* and the vibration is still there. Certainly on decal.

So, it would appear I need more rotation of the axle housing downward to better match the angle of the transfer case flange. Since I already have drop brackets, how can this be achieved?

Also, if I did go DC shaft, wouldn't I have to cut the ends of the axles and rotate only the third member to achieve the straight line between DS and 3rd flange? Otherwise I'd screw up caster?

Thanks all

 

[LandLocked93]

Well folks, I put another 4 hours into her this am and it's still problematic. Things I"ve isolated:

1) Spindle bushings - I pulled the spindles off and lubed 'em - so that's not an issue. I can confirm that they were self-lubricating
2) Grease in u-joints and slips - greased 'em all - no bueno

So, guess I need to order a CDL switch and remove the front shaft - where would a fella get one of those?

Many thanks!

Not able to suss right now that you've addressed, but looking at the pics, your front shaft is not in proper phase. It should be 90 out (unless a '97 is significantly diff from a '93?).

 

[Box Rocket]

UPDATE #3: Box rocket called it... I reinstalled the front DS, flipped the yoke 180* and the vibration is still there. Certainly on decal.

So, it would appear I need more rotation of the axle housing downward to better match the angle of the transfer case flange. Since I already have drop brackets, how can this be achieved?

Also, if I did go DC shaft, wouldn't I have to cut the ends of the axles and rotate only the third member to achieve the straight line between DS and 3rd flange? Otherwise I'd screw up caster?

Thanks all

A 'cut and turn' is certainly one way to address it, but shouldn't be necessary. There are many, many people here with a similar setup to yours that have not required a cut and turn of the axle.

If you currently have drop brackets to correct caster, it's possible you still don't have enough caster. You might look at caster plates instead. Either one will rotate the pinion downward if that's what you need to get the flanges parallel. Landtank plates from Wits End are available in a couple different setups for different lift heights.

I have a DC shaft on my own truck and the pinion isn't perfectly in line but it still works fine. The closer you can get it the better. I would just be sure that the ujoints are all in good shape and the driveshafts are properly in phase.

 

[Box Rocket]

These might be of some help in understanding phasing and proper joint angles.

Good video on how the ujoints work and setting proper angles.

 

[Jeff Elliott]

Thanks @Box Rocket , that video made it all make sense!

Now, is there any precedent for needing both drop brackets and caster correction plates? Based on my measurements, my pinion flange still needs to rotate down 4.2* to be perfectly parallel with the output of the t-case.

I don't think my lift is all that extreme but I didn't install it and don't know a ton about lifts. The PO said it has 50mm TJM progressive springs and MAF 30mm spacers. Wouldn't that work out to be just over a 3" lift? If so, the drop brackets should have been enough?

Thanks all

 

[bryson]

Thanks @Box Rocket , that video made it all make sense!

Now, is there any precedent for needing both drop brackets and caster correction plates? Based on my measurements, my pinion flange still needs to rotate down 4.2* to be perfectly parallel with the output of the t-case.

I don't think my lift is all that extreme but I didn't install it and don't know a ton about lifts. The PO said it has 50mm TJM progressive springs and MAF 30mm spacers. Wouldn't that work out to be just over a 3" lift? If so, the drop brackets should have been enough?

Thanks all

80 front driveshaft angles are tough... The OEM front configuration is a "broken back" style meaning that the angles are equal but opposite. This is a perfectly acceptable alternative to the parallel flanges (like the OEM rear configuration). However, after lifting an 80, keeping these angles in check is very hard. I'd bet that 90% of lifted 80s have at least some vibes coming from the front driveshaft, because it's all about compromise - when you change your pinion angle, you also change your caster - so most people live with a middle ground of "ok" pinion angle (i.e. still some vibes) while keeping enough caster to still drive straight and steady down the road.

Pic just for reference: the top config. is more standard, and is how the OEM rear driveshaft is set up (parallel flanges). Middle config. is the "broken back" that is used on the OEM 80 front driveshaft. BOTH are acceptable, and can be vibe free when done properly. The bottom image doesn't matter (it is showing parallel flanges like the top pic, only with incorrect joint phasing).

BUT, if you add a constant velocity joint at the t-case end, and you have to play by a whole different set of rules.

This link has a TON of great info, and will teach you enough to answer all of your own questions:

BillaVista.com-Driveshaft Bible Tech Article by BillaVista