 | Home > Technical > Remember the school bus sound , diff or something else? |
 
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| tatra805 Member Since: 16 Aug 2011 Location: Dolany Posts: 436   
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Need your thoughts on this one, all input appreciated.
After our offroad outing 2 weeks ago a sound appeared, very noticeable. I am guessing rear diff but would like to hear your opinions. Best described as the sound the schoolbusses used to make on overrun. but doubtly you were in the same bus as me 
I first suspected the handbrake drum as we hit it a couple of times. I dismantled the rear cardan / parking brake assy and found nothing suspicious. No play on the pinion bearing also. Sound is there when there is no drive power. freewheeling or cruising (so also in gear) the moment the slightest bit of accelerator is pushed the sound is gone. On overrun or freewheeling to a stop it is back immediately. Sounds as teeth matching with some freeplay at low speed and whining at high speed. Rhythm says ring and pinion, not wheel bearing or some other bearing. Lifted back wheel and have about 15 degrees slack, does not come as too excessive to me but i have no way of comparing here. No difference if transfer box is in H-N-L or with and without difflock engaged. As we had the stabi bars ups-side-down after the offroad trip i wonder if this might have pushed /pulled the axle forward and moved the pinion?? (radius arms are still straight, before you ask) Diff Oil fresh and clear, no metal parts. Hope to find confirmation or direction here, thanks!  |
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23rd Apr 2012 7:17pm |
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| tatra805 Member Since: 16 Aug 2011 Location: Dolany Posts: 436
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80 times viewed and nobody??
pleeeeaaaaaase somebody?  |
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24th Apr 2012 3:01pm |
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| tatra805 Member Since: 16 Aug 2011 Location: Dolany Posts: 436
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Thanks MK
Found out the diff has the bolt, not the nut. Tightened it to spec, it was lower than 70Nm. propshaft back on, testdrive and no difference in sound. 
Pulled the diff. Clearly the diff was already taken out before as the sealing is not original Diff itself is the original one stamped 12 2007, so far so good. Went for a 2wd drive, no sound. OK, wheel bearings and transfer case rules out. You were right. No damage to diff, all bearings look ok and absolutely ZERO scrap metal in oil/diffhousing. Observations Pinion has a uniform play of 1mm over the complete crownwheel. Increasing preload does not change this, decreasing reduces it but the pinion is then too loose. The sound is there, even when turning by hand. It disappears when there is almost no preload on the pinion. removed oil ring and 1st bearing, nothing abnormal to see. With the crownwheel horizontal, teeth up. While pulling the pinion to seat the rear bearing the grinding sound dissapears when i hold the pinion (without front bearing) lower. A similar but different sound appears when i go too low. The sound get worse when i pull the pinion up. leads me to think the diff is not set right and i have to go through the complete setup. Without having measured of used the blue stuff i think the crownwheel might be completely too far from the pinion??? 
Any recommendations before i venture into this? Did 2 diffs in my life and don't know how long they were running ok. 
Would have been the perfect time to put in an Ashcroft ATB, but their website says out of stock 
Guess it will be a good general training for when they have them back on stock All help welcome!! |
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25th Apr 2012 10:02pm |
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| MK Member Since: 28 Aug 2008 Location: Santiago Posts: 2395  
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You may try to run it as it is now (100Nm) for a while. Sometimes the whine goes away. At least mine did it.
I reckon mine was not properly thight from factory. If you think to start to do the setup, then I would advice you to have some shims with you. I think these are 49mm ID (not sure). Anyway keep us posted.  Puma 110" SW
............................................................. Earth first. Other planets later |
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25th Apr 2012 10:17pm |
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| tatra805 Member Since: 16 Aug 2011 Location: Dolany Posts: 436
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Thanks for the input
pulled the diff Setting was way off, which explained the 1mm backlash. Teeth were only catching on the top quarter... 
(no color available here so had to resort to grease)  Click image to enlarge After putting that straight (1 notch towards pinion was enough) the sound was still noticeable. Click image to enlarge 2 notches was too much and made the pinion teeth contacting the crownwheel valley. With the backlash gone i still had a grinding noise which was getting worse with increasing the pinion preload. Sprayed the whole diff with brake cleaner and that resulted in a screeching inner pinion bearing. While turning by hand. So shot bearing, no surprise. Putting oil on it made it quiet but the grinding feeling still there. The pinion was put without shims, so not much setting to do there. At set torque the preload seems ok. Put everything back as i need to drive in the coming days. Bearings ordered, hope they will be still here this week. LR was asking 93 euro for the inner bearing while at paddocks it costs 22,... asked the guy at the line if that included installation... he didn't get my point of course. 
Will update after installation. :) Admin note: this post has had its images recovered from a money grabbing photo hosting site and reinstated  |
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30th Apr 2012 11:15am |
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| Peter Td4 Member Since: 23 Oct 2010 Location: Antwerp, Belgium Posts: 227  
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Good luck with the repair
Peter,
Defender 110 StaWa - Td5 Defender 110 HCPU - Puma Defender 90 Soft Top - Td5 |
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30th Apr 2012 2:24pm |
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| Naks Member Since: 27 Jan 2009 Location: Stellenbosch, ZA Posts: 2623  
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Interesting take on the rear diff issue in the Puma:
from http://www.aulro.com/afvb/90-110-130-defen...ost1679163 -- 2010 Defender Puma 90 + BAS remap + Alive IC + Slickshift + Ashcroft ATB rear 2015 Range Rover Sport V8 Supercharged
Defender Puma Workshop Manual: https://bit.ly/2zZ1en9 Discovery 4 Workshop Manual: https://bit.ly/2zXrtKO Range Rover/Sport L320/L322/L494 Workshop Manual: https://bit.ly/2zc58JQ |
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8th May 2012 12:44pm |
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| tatra805 Member Since: 16 Aug 2011 Location: Dolany Posts: 436
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As follow up,
replaced both pinion bearings and while there drive flanges also. Sound is still the same
Means center is shot, i was already afraid when putting everything back, backlash of pinion and gear set and as good as 0, new drive flanges so not a lot of play there anymore also but when turning the diff once mounted i again had a 20° play on the pinion... From the sunny side; half of the job done. Now only wait for Ashcroft's TBA diffs to become available again and upgrade the center.
Mean time going to add a healthy portion of grafite and hope it makes the diff a tune quieter. Refrain from off road abuse for a month, drive carefully and knock wood the center doesnt go BANG in the mean time.
once more TBC, i guess |
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8th May 2012 9:56pm |
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| tatra805 Member Since: 16 Aug 2011 Location: Dolany Posts: 436
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Naks, Just went to the thread you referred to;
on page 1
I have less than 100km on fresh oil and it was.... silver when i drained it today. The old oil previously drained the same just a tad more dark. I do have TC, and it was working A LOT lately He might be right thanks for the link
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8th May 2012 10:04pm |
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| Naks Member Since: 27 Jan 2009 Location: Stellenbosch, ZA Posts: 2623
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Maybe, but not in my case: My Puma is now 2yrs old with barely 31,000km on the clock. Of that, we have done 3 mild off-road trails (2 sand, one rocky), with TC barely kicking in. In fact, I can count the number of times TC has kicked in when we are off-road on one hand - CDL is always locked and tyres deflated. The rear diff was replaced a couple of months ago and so was the gearbox. So no, it can't be the TC causing all these diff failures (at least in my case) -- 2010 Defender Puma 90 + BAS remap + Alive IC + Slickshift + Ashcroft ATB rear 2015 Range Rover Sport V8 Supercharged
Defender Puma Workshop Manual: https://bit.ly/2zZ1en9 Discovery 4 Workshop Manual: https://bit.ly/2zXrtKO Range Rover/Sport L320/L322/L494 Workshop Manual: https://bit.ly/2zc58JQ |
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9th May 2012 8:47am |
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| tatra805 Member Since: 16 Aug 2011 Location: Dolany Posts: 436
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Naks,
i can still agree with you, as there will be other reasons also causing diffs to fail. I don't know what happened to yours and what was damaged. As for landrover service; they wont open up a diff and start working on the internals, even wonder if they have anybody schooled on this. Replacing a diff is simply bolting in a complete new diff i was told when talking with the service over here. The guy also said that under warranty they would immediately replace the whole diff even if it is only an inner bearing being defect; less work to do and they send back the defect one to their supplier. When i saw how my diff was set i wondered how it could have survived that long. And it did not as this is also the second diff within 70 000km which is going. Somewhere on a forum or even on their website ashcroft is mentioning a batch of new diffs they bought from LR (as donor carriers for their lockers) where they found the majority badly set with premature failure being very very likely.(ring and pinion) As far as i am now i see - quality of materials - setting by supplier/LR - TC effects on the above saga continues |
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9th May 2012 10:12am |
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