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  1. #1
    Join Date
    Jun 2004
    Location
    Northampton
    Posts
    1,798

    Knocking from NS rear.

    Noticed quite a pronounced knock from the near side rear whilst trundling up the drive so parked up until I could investigate further. Seemed random and not related to a wheel revolution. Had it up on ramps with the wheels turning and it could be reproduced particularly in 3rd at tickover revs when it was labouring but with the noise of the side pipes difficult to locate. Took the wheels off and with the hubs spinning no knocking. Prop UJ seems tight and no excessive play on the diff output shafts although the bolts on both flanges were loose. Tightened but no difference. Perhaps the vibration may have loosened them. No play on both rear wheels and hub nuts tight. Sampled diff oil and although black no obvious metal fragments although left to settle with a magnet at the bottom of the bottle. Took it up the road gently but the knocking became continuous so had to make a hasty return. Any ideas? Wheel bearing? Diff? Thanks
    Dek

  2. #2
    Join Date
    Feb 2002
    Location
    Bradninch, Devon, U.K.
    Age
    72
    Posts
    2,346
    Driveshaft UJ
    CHRIS C - Maisie (DB No 46 )

  3. #3
    Join Date
    Jun 2004
    Location
    Northampton
    Posts
    1,798
    Quote Originally Posted by westborne View Post
    Driveshaft UJ
    Can’t feel any play on the driveshaft though. Perhaps I should jack it up under the hubs rather than the chassis so the driveshafts are in their normal orientation.
    Dek

  4. #4
    Join Date
    Aug 2004
    Location
    Christchurch, NZ
    Age
    59
    Posts
    2,445
    Have you tried greasing the UJs? They may be just a bit dry.
    Cheers

    Myles D-W

  5. #5
    Join Date
    Nov 2012
    Location
    Lanarks
    Age
    64
    Posts
    554

  6. #6
    Join Date
    Jun 2004
    Location
    Northampton
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    1,798
    Quote Originally Posted by mylesdw View Post
    Have you tried greasing the UJs? They may be just a bit dry.
    I haven’t Myles but would this cause such a loud knocking? Worth doing nonetheless. Thanks.
    Dek

  7. #7
    Join Date
    Jun 2004
    Location
    Northampton
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    1,798
    Sorry, that link is just an invitation to login to AMOC.
    Dek

  8. #8
    Join Date
    Nov 2012
    Location
    Lanarks
    Age
    64
    Posts
    554
    Seems a common fault Dek with our Astons...
    Sorry.....the photos will not load
    but I hope the following may solve your problem with these Jag back ends.
    -----------------------------


    Who hasn't experienced clunk noise originating from rear of DB7 at one time or another. Some claim noise is from differential, prop-shaft or half-shaft u-joints; others say loose or worn suspension components; a few offer up loose lug nuts or hub nut; and even fewer say handbrake shoes.

    Quagmire is, any one of above could plausibly be cause for "dreaded rear end clunk noise", and should be inspected by competent mechanic/technician with sufficient DB7 experience.

    However, before wasting monies searching for phantom problems, I've discovered majority reason for clunk noise is handbrake-brake shoes, which may or may not require adjustment. If at all mechanically inclined, this is a 11/2 hour exercise, and includes shoe adjustment.

    Raise vehicle to an elevation where you can reach one hand above juncture of propshaft and differential, then safely secure vehicle with jack stands, etc., should lift not be available. Place one finger on forward side of handbrake cable as indicated by red arrow, which is located between left and right Ration Levers, circled red in photo below. Now, press handbrake cable backwards, toward differential, then quickly release finger from cable; if noise emitted is identical to what you've been hearing in cabin when motoring in DB7, it is simply handbrake-brake shoe noise. It does not imply brake shoes are worn or require adjustment.

    Markup040.jpg

    However, if one wants to adjust shoe position, remove rear wheels, rotate rear brake rotor until "Hub Access Hole", circled red, is at 12 o'clock and aligned with "Handbrake Shoe Adjuster", red arrow. Use suitable width flat screwdriver (1/2") to insert into Hub Access Hole to rotate Handbrake Shoe Adjuster. Rotate adjuster "up to tighten", and "down to loosen" shoes. Tighten shoes until brake rotor stops moving freely, then loosen shoes just enough to allow brake rotor to move freely again. If uncertain, refer to DB7 Vantage Workshop Manual, page 5-43, for procedure.

    Rear brake rotor "Hub Access Hole", circled red:



    Concealed Handbrake Shoe Adjuster, and Hub Access Hole, red arrows:



    Perform brake shoe adjustment annually when changing oil and filter. Degree of difficulty: 1/2 wrench.

    Now you can motor around countryside with confidence occasional clunk noise is nothing more than normal handbrake shoe movement within rear brake rotor drum

    Happy motoring,



    Mar 31
    When adjusting the brake shoes, tighten up the adjuster until the disc is "just" too tight to turn by hand then centralise the shoes. Do this by either a series of gentle whacks around the drum or by pulling the handbrake a few times. Chances are you will have to do this a few times each side.
    It's a good idea to remove the drum occasionally to make sure all is OK inside. As the shoes last so long, various parts can sieze up. Get it all right and the handbrake works quite well. Helps when turning the car round too. Yes, you can handbrake turn a DB7 but don't blame me if it goes wrong.




    When adjusting the brake shoes, tighten up the adjuster until the disc is "just" too tight to turn by hand then centralise the shoes. Do this by either a series of gentle whacks around the drum or by pulling the handbrake a few times. Chances are you will have to do this a few times each side.
    It's a good idea to remove the drum occasionally to make sure all is OK inside. As the shoes last so long, various parts can sieze up. Get it all right and the handbrake works quite well. Helps when turning the car round too. Yes, you can handbrake turn a DB7 but don't blame me if it goes wrong.

    John:

    You're correct on both accounts. Whacking rear rotor/drum with mallet will loosen handbrake shoes, and tends to center shoes too. It's good practice to remove rear rotor for disassembling handbrake shoes. It allows one to remove any crud accumulation and cleanup parts. My preference is if reusing parts, wire brush clean and soak parts (except shoes) in WD40, allowing parts to dry thoroughly before reassembling. And as you say, handbrake works like new. As a rule of thumb perform above task when brake discs are showing 30-50% acceptable wear.

    Bill

    Just for the record - there are grease nipples at each end of the prop shaft and IF these have been permitted to get dry, there is often a clunk when taking up the power. Give them a good dose of grease every year

  9. #9
    Join Date
    Jun 2004
    Location
    Northampton
    Posts
    1,798
    Thanks Drammyboy but I think the clonking is far too loud and continuous for it to be brake shoes. But all suggestions help!
    Dek

  10. #10
    Join Date
    Nov 2012
    Location
    Lanarks
    Age
    64
    Posts
    554
    or possibly

    Rear end clunk noises usually come from LOWER trunnions, because the powerlock LSD axle inhibits clonks.
    In there, are TWO back to back Timken taper roller bearings which NOBODY ever services.
    I have seen many in an absolutely dire and disgusting state.

    and then we have.....(again from DB7 folks)

    The 'Rear End Clunk' for me took ages to track down. Turned out one of the 4 lower bolts securing the diff to the subframe had worked loose, and another was sheared off.

    ------------

    I have come across only 1 XJS axle with one of those large countersink bolts broken.


    All the best in finding that clunk.

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