Another spellbinding round of diagnose the noise!

[Brianmitchtay]

Good evening, gentlemen!  (or morning to everyone in the land of Oz)

Welcome to another round of diagnose the noise! If you're keen to humor me feel free to read on

Here's the context :  The outer boot of the original passenger CV axle broke, and was driven on for probably longer than it should have been, plus I currently live in an apartment where I am not allowed to work on my own vehicle, so I had a local Subaru specialty shop put a new axle in for me. I couldn't find an OEM axle so I had an import direct axle from Oreilly put in (and have the old axle in the closet so I can rebuild it for a spare). On the drive home I noticed a new noise and went back to the shop the next time I was in the big city, they said that their best guess is the noise is from my engine "slapping around" due to not being completely mounted and that they would install the two missing motor mount bolts for the low low price of $450 to see if it helped, and that they would not diagnose the noise further until I had the bolts installed. It's true that I only have the front bolt installed on each motor mount bracket, but I've now driven over 25k miles like this without issue so I'm pretty dubious about their diagnosis.

Here's the noise :  (Pretty similar description to this other recent post I found digging through the search today)

A rhythmic/speed related, knocking/ticking, it gets louder and faster as you move from 5-25mph, then continues to get faster and never really goes away, but disappears into the blur of road noise from 35mph and up, the pitch doesn't change ..just the speed. It seems to match tire rotation speed. Once the car is warm it quiets down a bit, and so far has just been a noise, no drivability issues. After about 1200 miles now it's starting to get noticeably louder and worse.

And the conditions:

-It only happens when the engine is under load, if you're coasting down hill, or foot off the gas, or the second you take it out of gear, the noise is completely gone.

-It gets a bit worse making right turns, and almost completely goes away making left turns

I have a pretty good guess that my problem is a crap aftermarket axle that's been noisy from the day I had it put on, and the shop that put it on just doesn't want to deal with my old Subie anymore, (not sure why because I love this old thing) but I figure I should post here and see what you all think - if you're not sick of guessing at my old '87 GL's quirks yet. The only reason I'm not totally confident about it being the inner joint of the CV axle is that it completely goes away if the engine isn't under load and I have a hard time imagining how an axle that sounds that bad under load could somehow be completely quiet just because it's coasting.

Any thoughts are welcome, thanks as always gents.

   

[el_freddo]

Evening (and a late evening from the east coast of Oz - 10pm-ish here!)

The issue you describe does sound like a drive shaft - particularly since the replacement item was an after market unit.

I agree with you, the missing engine mount bits won’t matter, so long as the engine is still held on either side of the engine mount by one nut and washer setup. 

Other things to consider are:

- tail/prop shaft uni joint on the way out. Although that’s not powered when in 2wd, so it’s a long shot

- excessively worn gearbox mounts

After reading that linked thread I think you’ve already got your answer - and it all points at the after market cv shaft.

Bugger about not being able to work on your car at your apartment :/

Cheers 

Bennie

[DaveT]

The description reads like front axle. 

Aftermarket axles are instantly suspect.

I never ran one with missing engine mounting bolts, but the noise matching wheel speed makes no sense if it coming from them.

 

[Len Dawg]

Wheel bearing..  turning right/left is the key. I would hit the local parking lot and jack up the front to do the 12-6 9-3 o'clock check, pretty sure they didn't replace the cone and it's loose... Hell I can almost bet they didn't repack or replace the bearing seals .. without looking at paper work. 

Kinda weird the mount bolts were missing..

[DaveT]

Good idea, check the axel nuts.

[Brianmitchtay]

11 hours ago, el_freddo said:

Other things to consider are:

- excessively worn gearbox mounts

Yeah I had looked at them and they definitely look a little worn, but I hadn't realized how much of a problem that could be. I'm beginning to suspect that it could be very spongy and loose transmission mounts causing the inner DOJ of the new crummy axle half shaft to wear excessively.

I think I'll order one of the A1 Cardone Reman axles from Rockauto, along with new transmission mounts, and then try to do it all in one fell swoop. Good news about the Oreilly CV axle is it has a limited lifetime warranty, so at least I can get my money back!

Maybe if I beg on the local community facebook page someone here in town will lend me their garage for an afternoon so I can get out of the rain. All the auto shops here are booked out for almost the next month completely -  "Tire changeover season" - Welcome to Alaska I suppose.

Thanks for the insight guys.

[Dee2]

 

14 hours ago, Brianmitchtay said:

A rhythmic/speed related, knocking/ticking,

I had a similar problem when I replaced my axles.  The solution I used was to slightly overtorque the retaining nut.  With that I was able to silence the noise. 

Before you do though, you may want to check the bearings.  Grab hold of top of tire and push and pull hard.  If it goes klunk klunk, then you need new bearings.

Otherwise, check your torque on the axle castle nut.  Sometimes you have to slightly overtorque to get things to quiet down.  I torqued mine to 145 ft lbs, then moved to next free slot on the nut to get the pin in, but before I put the pin in, I rotated one more notch, then pinned it.  Seemed to make a big difference.  Not 100% quiet but I  can live with it.

You may also need to check the washers beneath the axle nut.  Some folks say they replace them and lose a lot of noise.

Edited October 25, 2018 by Dee2

[el_freddo]

Torque should be 196 ft lbs from memory.

Worn gearbox mounts won’t make an inner CV wear quicker, it’s designed to work on an angle! The issue is the aftermarket shaft. You might find that this shaft slips in and out of the bearings easy, when they should be a solid fit where you’re using a mallet or the like to get them out. 

Further, if the cone washer has a lip on it you’ll never get the job done properly in terms of torque/clamping.

Cheers 

Bennie

[Dee2]

On 10/25/2018 at 10:41 PM, el_freddo said:

Torque should be 196 ft lbs from memory.

145 ft. lbs. = 196 N.m

Edited October 27, 2018 by Dee2

[el_freddo]

Thanks Dee. I knew it was something like that... I have a 3/4 inch drive breaker bar that I jump on to tension the castle nut, my torque wrench doesn’t go up that high :/

Cheers 

Bennie

[Brianmitchtay]

I haven't had a chance to take it apart and give it a better look yet (It'll be a bit harder now that there's 6 inches of snow on the ground) but tonight I threw on the 4wd to drive home in the snow and that also completely kills the noise. 

 

Weird, eh?

[DaveT]

Not entirely.   4wd puts a different load / shifts the loading on the driveline parts.

 

[Brianmitchtay]

23 hours ago, DaveT said:

Not entirely.   4wd puts a different load / shifts the loading on the driveline parts.

 

Yeah I see, just did a fair bit of reading around the web related to part time 4wd/without a center differential and how that changes/creates stresses like driveline bind and it actually makes pretty good sense. I think I've not been cautious enough about avoiding the use of 4wd in situations with decent traction! I swear every time I learn something new about cars I feel like it's a miracle this GL hasn't exploded yet from me abusing it.

I guess that means the next car will last even longer than this one does! Since I'll have such a better idea of how to care for it ;D

[DaveT]

Only use 4WD when wet, or on snow ice off road.

Most of the time, when raining,  I'll switch it on while stopped, get going,  then switch off.  Unless there are big puddles or water sheeting on the road.

[jono]

I still keep a 'diagnosis' CV shaft for eliminating suspect new CV shafts. Might take 45 min to swapbut has fixed problem each time and suspect axle is out ready for warranty. Good idea to fit those engine mount bolts before they do bite you. $450 ! You need to turn up in cheaper threads maybe?