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Naks

Groaning noise on Ashcroft ATB

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Hi chaps,

I'm hoping someone here can help me with an issue I'm having on my Puma :)

I fitted an ATB in the rear of my Puma in October 2017, and recently started noticing a groaning noise that's becoming quite bad. 

My indie and I eventually traced it to the rear diff: at specific rpm/speed, there is a loud, low-frequency groaning noise + vibration emanating from the rear of the car. It almost feels as if the seats have built-in massage function, especially when I hit 80-100kmh. 

Has anyone else experienced this after fitting an Ashcroft, and if so, how did you fix this? 

thanks

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Not specifically the ATB, but the 'Puma' rear diffs are known to fail in fairly short order, I believe it is bearing related.

So... If they weren't changed when you fitted the ATB, then this is where I'd start, and fairly soon, and bits of collapsed bearing will probably not do the ATB much good...

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Thanks Bowie, bearings were replaced when the ATB was installed.

My indie used Timkem ones, IIRC.

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Just a thought, if it happens when driving straight the diff itself isn't involved. Could this be a wheel/tyre issue, or propshaft - something out of balance?

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I have the same ATB (though mine is in a Series)  and haven't noticed any noise from it. But the first thing I would do in your case is drain the diff oil and have a look, it might be very costly to keep on driving with it. If there is any any metallic parts in the oil you should stop using it immediately IMO

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Thanks,

Car was serviced on Monday, diff oil was changed after 1000km on the ATB - no noticeable particles.

I removed the rear prop and had it tested, no issues. All tyres were balanced today as well, to rule out tyre wear.

Ashcroft say it's probably the backlash on the crownwheel & pinion.

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Hi, 

not so much backlash, it’s the crown wheel runout that may need checking

Dave

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Thanks Dave, will get him to check that asap!

 

Sorry, my mechanical knowledge is zilch, so I thought the runout & backlash were the same thing.

Edited by Naks

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Runout is the weeble-wobble side to side of the crown wheel, measured with a dial gauge on the back face of the crown wheel.

Backlash is the movement present between the pinion and crown wheel, measured against a tooth of the crown wheel, while rocking it back and forward with the pinion held firm.

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Just spoke to my indie and he says all the adjustments were done during the fitment... so he's going to take it out and inspect it.

I kept the original diff, so we have the parts if the diff carrier needs to be replaced.

Edited by Naks

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I had a 2009 90 with a recurring rear diff issue - the rolled pin that secures the diff cross pin kept shearing.  I suspect the cross pin or the hoses in the carrier were slightly worn and pin movement was shearing the roll pin, but it all looked and felt good on disassembly.  Anyway, the cross pin would slide out and be held against the inner edge of the ring gear, where it would contact the pinion head.  It left a pattern on the pinion and chipped the edge of the pin.  That repetitive hammering might have an effect on the pinion bearings.  If you had anything similar with the original diff, then the pinion might have been upset but not noticed, as it wouldn't normally be adjusted for fitting an ATB.

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Just got an update from the workshop: they fitted a new crownwheel + pinion and the problem is gone, plus one of the bearings was not sitting properly (not too sure about the exact terms).

the original diff was replaced by LR after about a year of ownership, so not sure if that was not done properly, and after 9 years it finally went over when the ATB was installed?

my indie says now that the droning noise from the diff is gone, there's a 'squeaky' noise that's appeared, and he thinks there's a bearing in the gearbox that needs inspecting  :rolleyes:

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You said the noise started after the ATB installation, not before, and that a bearing was not seated correctly when they took the ATB out to find the problem.  A mis-set bearing would cause such a noise and could also cause damage to the gears.  They didn't find any problem with the gears on the first installation of the ATB, and you had no symptoms at that point either.  My suspicion is that they caused the damage by not fitting the bearings to the diff correctly and are passing the bill for their error and the new gears on to you.

It's quite possible that the damage has spread to other components, but before stripping the transfer or gear box, I'd check the prop shaft UJs- they are prime sources for squeaks if dry or the needles have skewed.  Transmission damage is less likely.; squeaks from there are unlikely as the bearings are seldom dry!  I have a feeling they're either incompetent or are taking you for a ride as you haven't grilled them over their diff errors.

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1 hour ago, Snagger said:

You said the noise started after the ATB installation, not before, and that a bearing was not seated correctly when they took the ATB out to find the problem.  A mis-set bearing would cause such a noise and could also cause damage to the gears.  They didn't find any problem with the gears on the first installation of the ATB, and you had no symptoms at that point either.  My suspicion is that they caused the damage by not fitting the bearings to the diff correctly and are passing the bill for their error and the new gears on to you.

It's quite possible that the damage has spread to other components, but before stripping the transfer or gear box, I'd check the prop shaft UJs- they are prime sources for squeaks if dry or the needles have skewed.  Transmission damage is less likely.; squeaks from there are unlikely as the bearings are seldom dry!  I have a feeling they're either incompetent or are taking you for a ride as you haven't grilled them over their diff errors.

That’s what I had thought - thus this post earlier ....

On 01/02/2018 at 6:30 PM, Anderzander said:

Has your dealer built the diff properly?

 

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Yup, your indie naffed up the bearing preload/fitment...

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Yeah, it is likely, as this was the first ATB they had ever worked with...

if this was their fault, that's the first time in 10 years/4 vehicles that they might have messed up... :wacko:

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It won't matter whether its an ATB or a standard diff when building... the approach will be the same?! Locker is slightly different with the air bits to sort but the main bits are still the same.

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17 minutes ago, Naks said:

Yeah, it is likely, as this was the first ATB they had ever worked with...

if this was their fault, that's the first time in 10 years/4 vehicles that they might have messed up... :wacko:

Sounds like it may be one to take on the chin then...

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As Ross said, there is absolutely no difference between fitting an ATB and a standard diff.  Any bearing seating fault is the installer's fault.  Anyone can mess up, but they are making you pay for it and lying about the nature and source of the error.  They should have paid for the costs in the second visit, including the new gears.  That they are trying to get you to pay for a full gear box removal and strip down for an unidentified squeak is reprehensible.

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OK

If the pinion was left alone, then its not height or preload that is wrong.

IF the head or tail bearings were changed them you need to height block to check / and reshim head height to what is WAS not 0.0 and then preload would also need setting. If none of this was distrubed then read on.

 

A centre is a centre, Locker ATB LSD 4 pin the process the basically the same with differences ...

The 2 x carrier bearings are adjusted via adjuster rings to set the back lash.

 

The back lash MUST be measured with a dial gauage and set correctly, the back lash is what gap there is fron rocking the cwp back and forth in a click - clock sort of noise, typically set to 4-6 thou backlash.

Now, the dial gauage we use we check 6 quadrants, ie 12 o clock 2 4 6 8 10 o Clock

Each will give its own reading 

good to brilliant would be say 5 5 5 5 5 5 = 0 backlash

but unlilley you get 0, so its the highest vs the lowest 

ie

5 8 5 4 5 4 = 8 high 4 low = 4 thou Run out + too high.

 

Running with bug run out / tight spots will quickly kill crown wheel and bearings too :(

My guess is he didn't do the above properly, and you will find massive backlash AND run out variances.

 

In which case he needs kicking ion the crown jewels for being a Knob :D

 

Nige

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