Drone at Hwy speeds, long.

[XJJack]

Check your brake pad slop.
You can check this quickly by just pushing your brakes a bit while doing 80-90 and see what happens to the sound.

 

[JEEPTUBE]

Mine does the same thing, i have a 97. After puting all the stuff i had off my 92 onto my 97 it still freakin vibrated. Basically i replaced everything underneath the 97 including the whole axles and t-case. I swear the newer XJ's are posessed!!!!!
ITS PROB THE TRANSMISSION!!!!!!! AHHHHHHHHHHHHH! im gonna kill mine!!!

 

[jeepnuts311]

does the sound get worse when you let off the gas and coast? moms 95 xj has the 8.25 and it sounds nasty

-tim

 

[Rawbrown]

ok, couple more questions. Just let me walk through a few things. yes I might ask question or two thats the same but sometimes things are for clarafication.

is the drone sub audible or really bassy'? is there any vibration associated with it? does the tone change with road speed? does the drone change when coasting? or is it right at that point between drive and coast?

 

[Angus]

The tone changes very little between coast and power. It starts as a low tone osilation at 65. As speed increases the volume increases, but the pulse decreases. At 80 (had to test it right) the pulsing is almost nil and the tone is a near constant low drone or hum. It is low enough to almost hurt the ear, similar to opening a window at highway speeds. I have been on duty or celebrating a 3year old b-day so I haven't had time to play again. I am leaning hard on the rear TC/SYE bearing since it has been constant in all tests and I want to reseal the TC anyway.

Thanks

 

[XJJack]

When you are done playing with that, fix the brakes and git rid of the noise.

 

[XJeremy23]

These kind of things are hard to troublshoot when going off a description of the sound. A guy would almost have to hear it for himself to get a good idea. I hope you do figure out what is wrong. Don't mean to steal the thread but I had a question for Rawbrown regarding the descriprion of the sound. What would you say was wrong if the sound was between drive and coast?

 

[MaXJohnson]

Vehicle: 6cyl, Auto, 4:11 gears, BFG 31 AT's
Problem: Slight vibration @ 50mph, loud drone @ 70mph. The drone is low frequency that oscillates every 2-3 seconds. The original LP D30 and 3:55 gears had same condition, just at different speeds of course. Drone is in the rear.

Swapped 2 then 4 degree rear shims along with longer shackles. No real effect other than tone.

"drone @ 70MPH that oscillates every 2-3 seconds"

The fact that the sound oscillates every 2-3 seconds would make me think it's u-joint related. Bearings, seals, gears, brakes, etc would not have an obvious oscillating mode.

Some new car dealerships have test gear that can measure the frequency and magnitude of vibrations. If you can find the frequency of the drone you described, you can compare it to the following calculated values:

13.3Hz - tire balance or out-of-round
26.7Hz - 2nd order tire vibration
40.0Hz - 3rd order tire vibration
41.1Hz - driveshaft balance
82.3Hz - u-joint wear or out-of-phase (angle)
92.5Hz - 6 cylinder power stroke

These values are based on the rev's per mile of your 31" BFG's (actual diameter of 30.7" minus .2" wear estimate) at 70MPH with 4.11 gears and .75 overdrive ratio. The 13.3Hz tire balance frequency is too low to be audible(drone per your description), so I would eliminate it.

I'm betting the drone is around 82.3Hz

 

[Angus]

OK some more info since I started this. Once the drone has started it does not matter whether its under power or coast. I can also apply the e brake with no effect. I also can tow my boat with no change in the tone or volume. I think this is significant since the boat changes the u-joint angle by the load on the springs. If anything the angle becomes negative, but Ive never measured it when the boat is hitched.

Thanks, Angus

 

[Terrific]

What kind of brush guard is this? It looks good. How sturdy is it?
I'm looking for a brush guard that will mount to the unibody and allow me to keep the stock front bumper.

Did you check the ring gear for "run-out" when you did the install? I set up rear ends and I'm thinking something in the diff. Also, Woods builds different shafts for different uses, If you got one, say for crawling, it would be smaller diameter and thicker tubing and harder to balance. The one I installed on my 96' was built more for street and light trail use, thus having larger diameter and thiner tubing, easier to balance.

I'm not being critical just trying to find a solution.

You have a very similer set up to my 96'. Except the front is open and Tru-Trac in the rear(4.10 and 30"), and I'm running mixed bag OME/ACOS/TeraFlex 4.5" lift.

 

[anderld47]

OK some more info since I started this. Once the drone has started it does not matter whether its under power or coast. I can also apply the e brake with no effect. I also can tow my boat with no change in the tone or volume. I think this is significant since the boat changes the u-joint angle by the load on the springs. If anything the angle becomes negative, but Ive never measured it when the boat is hitched.

Thanks, Angus

Did you ever put a dial indicator on the yolk shaft of your sye?

Or think about keeping all your post OEM stuff and putting it on a different xj? Kidding!

Sure it wasn't happening stock, but you just weren't listening for it?

 

[Ivan]

I haven't read through all the post, but have you removed the rear diff cover to inspect the pinion and ring gears?

After a regearing, my diff developed a similar droan at varying (but sinusoidal) speeds. Ultimately, it turned out to be the adjustors on my 8.25 had worked loose and booger up the R&P.....

 

[Angus]

OK, I'm baaack.

Got bored and decided to check the TC rear bearing more thoroughly. I grabbed the output and shook it all over. The yoke had minor movement both radial and thrust. I do not know the exact tolerances by feel, but I needed to reseal my TC case half so apart it came. The case internals looked great, no slop in the chain and everything checked out. I have rebuilt many of these so I have no question. The rear bearing spins fine, but there is a minor amount of thrust play and a small "catch" that I do not like. Anyway I'm cleaning everything and installing a new rear bearing and seals tomorrow. I only give this work a 50/50 chance of fixing the osilation, so the yoke is next in line. I hate the diagnoses by replacement, but no smoking gun has shown up yet. Please review all the post because I have done everything short of puting the output shaft and yoke in a lathe to check runout. (I had little luck trying that on the truck) I hope 32 spline 1310 CV yokes are not to expensive or hard to find locally?

Angus

 

[Angus]

OK, 90% of the drone is gone! After inspecting everything in the TC I was very sceptical that anything would be solved. I guess the very minor "catch" in the rear bearing was enough. After cleaning the bearing I couldn't tell if the "catch" was real since it only did it half the time. Anyway, I ran the truck up to 80mph and there is now only a slight vibration. I am going to fine tune my axle shims today. My rear u-joint is at 0 degrees angle while sitting so I am going to give it 2 degrees for running torque. That may be the reason for the vibe only starting at high speed/torque. I'll let you know.

Angus

 

[anderld47]

Sounds like being part pitbull is working out for you... Keep it under 80 and enjoy it!