rearend noise??

[65er]

  I had a droning noise that I had been chasing for a while.  Sounded like the car just started to roar inside pretty suddenly when I hit 58 mph.  Sounded about like driving over those rumble strips designed to wake up up if you drift on the highway, but continuous and only about half as loud.  Seemed to be most unhappy right at 60 and would decrease slightly as speed increased up until about 80 the roar was about half as loud as it was at 60.  It might continue to get quieter at higher speed, but 80 is as fast as I checked it.  In chasing down the noise I replaced my pinion yoke, upper and lower control arms, adjusted driveline angles up and down as well as left and right, and also replaced my driveshaft.  What finally fixed it was putting the old pumpkin and axles back in.  Turned out that was a pretty good call since the old pumpkin is an open diff and I put it in the day before the ice storm hit...

  About the stuff I took out:  True Track diff, 3.89 gears with a Daytona pinion support and Moser 31 spline axles. All the stuff was brand new, assembled and installed by me about 7000 miles ago.  I don't drive on the highway all that much, but it seems like the noise started around the time I did the upgrade.  If not, then it started soon after because it had been making noise for quite some time. 

  Now my question... what the heck can be making that noise?  Maybe a bearing race not installed perfectly true, or a bad bearing somewhere or the true track diff its' self?  But don't bearings only get louder with speed instead of peaking and backing off like a balance problem?   I was careful in the bearing installation and even checked runout with a dial indicator so I'm sure at least when I put it together the bearing races were true within .001".  The axle bearings feel nice and smooth tuning them by hand, and the whole pumpkin unit seems to turn perfectly nice and smooth.  I've even had the pinion support out of the case to change the pinion yoke and it also feels perfect with an appropriate amount of drag torque.  I'm hoping I can tear the pig down and come across something obvious, but if anyone can offer specific stuff to look at, I'll be sure to check those items out extra  close.

   The only other thing I could think of was maybe the wheels moving around on the axles, since the lugs on the 31 spline axles are a bit longer and I have closed-ended lug nuts.  But the wheels always felt secure when I've put them on and I couldn't see any evidence of stuff sliding around between the aluminum wheel and the brake drum.

[machoneman]

Have you tried to 'read' the ring gear's tooth pattern?

 http://www2.dana.com/pdf/5717.pdf

Maybe post a good close-up pic. If all that looks good, a rumbling sound could indicate rough axle bearings. Pinion bearings tend to whine, not rumble while bad gears tend to make noise on acceleration or deceleration or all the time. Check the bearing races closely on the axles, again for an odd wear pattern or pitted races. Sometimes the bearings get damaged on installation (whacking the axle end to get them to seat) or the bearing housing end where the bearing sits gets messed up. Odd though the old parts don't do the same thing, meaning maybe the whole issue is in the third member.   

[My427stang]

First thing I would look at the wear pattern, post a pic here if you can

Second, feel for play in the pinion bearing, check backlash etc.

Last, check to see if the axles are straight, I had one in my truck years back that was bent, a little tougher to get in than the other side, but not bad, but it made an odd grown under load

[65er]

   The drone really sounds like something out of balance shaking the car body but a lot higher frequency than a tire.  I forgot to mention that when it was happening, it didn't matter if I was on the gas or off it, or even out of gear coasting with my foot off the gas.  I was sure it must be an out of balance driveshaft or bad driveline angle until after I changed those things.  Seems like if it was the ring and pinion making the noise the gears would have been toast long ago?

The gears do whine just a little, but not bad.  When I set it up, I set the pinion depth according to the marking on the gear and set the backlash on the ring gear to spec.  I also checked the contact pattern which looked ok but maybe a little marginal.  After I drove it and found that it whined a bit, I pulled the pinion support out and gave it an extra .002" shim to see if it would quiet the gear whine but I don't think it really changed much if at all.   But I'll try to get pics of the gear contact pattern this week in case it may tell something.

As for axle bearings, Bob, do you mean the carrier bearings maybe instead?  The axle bearings are permanently sealed, so there's no way I can look at the races.  They both feel maybe a little tight, but I can't feel any roughness in them at all.

Ross, there's no play in the pinion bearing for sure.  I've had the pinion/support assembly out a couple times and the preload is right and it also feels smooth.  I do plan to have a look at those bearings though when I tear it all down.  Before teardown though, I'll be sure to check the backlash again while I get the contact pattern pics.   I can check the axle straightness easily at my workplace, I'll do that this week for sure. 

Another thing I was wondering about is the differential its' self.  Is it possible that the true track unit could be making that noise?  May rapidly locking and unlocking or something?

[e philpott]

since it doesn't change pitch on or off the gas , I would look at the carrier and axle bearings real close ....... I would have listened to the rear axle on a lift with a driver and stethascope , get it up to 50 60 mph and move the probe by the axle bearing to see if its louder near the axle bearings or up by the carrier

[machoneman]

As for axle bearings, Bob, do you mean the carrier bearings maybe instead?  The axle bearings are permanently sealed, so there's no way I can look at the races.  They both feel maybe a little tight, but I can't feel any roughness in them at all.

Both. Agree with E.Philpott that getting the car in the air and running it would be very helpful. The carrier bearings/races are relatively easy to check of course (given the pain of taking the pumpkin  out again!).  Checking the axles for straightness is a tad harder but one could get a lathe setup or a pair of v-blocks and a dial indicator. On the axle bearings, I should have been clearer. It's the i.d. of the 9" rear end housing's axle bearing ends where the o.d. of the sealed bearings ride. Sometimes a burr will prevent the bearing from seating correctly.....although again if the replacement old axles pretty much slid in and with the old pumpkin the noise went away it's likely not the burred-up or misaligned housing ends. 

[Cyclone03]

When you changed the chunk did you also change the ratio?
My Mustang has a 3.70 gear and over drive transmission. I drove it for over a year around town and to Houston and Austin. I had some noise in the rear end at around 70MPH but was no real problem. I then drove the car to California and found it was noisey at 75-80mph but at 85 it was unbearable. Just WAH WAH WAH...
I figured bearing,set up pinion angle. Nothing helped.
This year I rebuilt it all,again, and changed to a Daytona Support, the yoke I used was a 1330 size so I had to have the end on the drive shaft changed.
I mentioned the noise to my drive shaft guy and he went  ahead and spun the shaft for me before he swapped the end. The balance was ok at a shaft speed of 3000rpm but was too far out for 4000rpm.
New balance factor and Im good to a tested 90 now.   

[65er]

I really wanted to run the car with the wheels off the ground but the only way I could do it at my place would be to put it on jackstands.  I didn't feel too good about that idea though and had visions of my car smashed into the $300,000 5 axis milling machine that would be in the path of the car if it got loose.  Not to mention climbing under there to listen.  Yeah, I'm a big chicken, lol

Since I do work in a machine shop though, checking the axles will be easy for me.  One thing that stands out to me since you mention it, Bob, is that the bearings on the new axles are wider than the old ones.  They fit snugly in the housing just like the old ones, but they stick out of the brake backing plates by about 3/16" to 1/4".  It didn't happen before, but this last time when I pulled the axles out the passenger side backing plate came loose from the housing.   I could now see that when I tightened down the axle retainers, the backing plate still had some room to float around on the bolts.  The holes are a close fit on the bolts so it doesn't have much room to rotate with the wheel, but it may have been moving in and out a little.  Doesn't seem like there would be anything trying to force the backing plate in our out, but if it were to flutter for some reason then that could sure do it. 

On the axle bearings, could they be bad and still feel smooth?  Also I had always thought that a bearing noise would only get louder as speed increased, not go away like a balance issue can do.  If it seems likely that an axle bearing could really be the problem then I may get some stock replacement axle bearings and install those in place of the wider more heavy duty looking bearings that are on my 31 spline axles.  If I put the axles back in with the wide bearings they have now, I'll definitely fab some spacers first to take up the difference in the bearing width so everything clamps up properly.


My heavy duty setup has a 3.89 ring and pinion setup while the old one I put back in has a 3.64 so yeah, I did change ratios a bit.  If it were a driveshaft related problem, I figure my noise should have moved up by about 4 mph.  I tested it up to about 75 and whatever it was is definitely out of there.  The driveshaft by the way has 1330 u-joints at both ends and since I was chasing a problem and wanted to be SURE it wasn't the driveshaft, I went plenty overboard.  It's a 4" x .125 wall aluminum unit with high speed balancing from Driveshaft Specialist in San Antonio.  Probably good for 200 mph, lol.  Didn't make a bit of difference but now I do have one hell of a nice driveshaft!

[machoneman]

Find a friendly shop with a frame lift and run it up.....I'd hesitate doing so in my garage too yet one could do so outside with a pal inside and the car pointed to a safe place.....just in case. Don't like to hear about those wide bearings either as that is a strange deal.

Story time! My uncle Bill runs a small water pump, gas engine and hi-tension power utility supply co. locally and they had a few of those really long bodied Dodge cargo vans for deliveries. Normally, the vans run on city streets but sometimes on the highway.  Bill drove one of the vehicles on the highway a few years ago and noticed a really odd vibration at speed. Took it to the local dealer and said fix it. Well, after numerous visits w/o any luck since the mechanics could find nothing wrong, the delaer called and said the factory rep. would be in town the next day. Back to the dealer and after a test drive and his inspection, voila!

Seems that the vibration occurred only after the van had been to the local lube oil change place. When they lifted the van, one of the two-post side lift (you know, the kind where the side arms must be adjusted in/out and fore/back) 'fingers' did hit the OEM aluminum driveshaft and put in the tiniest of dents! Previously, the dealer's mechanics missed the dent but did have a local balancing shop run up the driveshaft.  They did not though have the shaft spun up to anywhere near the speed it needed to be to equal highway speeds.  One new d-shaft and that was that!     

[65er]

Here's a pic of the bearings side by side.  I like the O-ring seal on the new, wider one but have no way to know if it's any heavier duty inside or not.




If it has noise again next time I swap out my stuff, I'll try to get it to someone with a lift so I can listen to different places along whole rearend.  If it does turn out to be an axle bearing, at least I can change that without pulling out the pumpkin.   Also I'm thinking about going back in with a locker instead of the true track.  The t.t. drives smooth and quiet (unless that's the source of my highway noise, which I kinda doubt) but in addition to its worm gear mechanism it also has friction like a track-lock or posi to keep both wheels turning even with no load.  I was hoping for a unit that would act like an open carrier until it had some torque applied but that's not how this one works.  Come to find out most of the true tracks can act open, but the Ford 9 and a couple others are set to around 100 ft/lb minimum breakaway torque.  It's actually stiff enough that I can feel the difference in the steering the car.   It will turn without chirping the tires, but it really wants to go straight all the time.  I'm thinking I might actually like a locker better for driving around town.

[jayb]

+1 on the Detroit Locker!  I love the ones I have, and wouldn't have anything else in the back of my cars, save for a spool in a more radical vehicle.

[Cyclone03]

Are you in/near San Antonio?
I'm in Cibolo,Bill at DriveShaft Specialist set mine up.

As for bearing sticking out,Im useing Strang Axles and the bearings do not sit flush with the housing.I have Mustang Steve disc brake backing plates and they are counter bored to clear the bearings.

[65er]

No sir, I'm not really close to San Antonio, I'm just North of Dallas and Ft Worth in Denton.   I still have the original drum brake setup on my car for now but I hope to eventually upgrade the entire brake system with more high end stuff all around.  I have the Scarebird setup on the front right now and it works fine, but I'd like to run larger rotors in front and upgrade to something a bit better than "fine".