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My Rear-End is Knocking

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arbs_53

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How's that for a lead-in! Before I get a bunch of comments on my 53 year old posterior, let me explain. I had the differential unit rebuilt a couple of months ago on my TR250 because my original one had what was called "excessive lash". The replacement unit, from a TR6, I was told, only needed new shims and a couple of bearing carriers to get it back to tolerance. It came back and was installed at the same time that I had a garage press in four new u-joints in the half shafts, installed Richard Good's adjustable trailing arm brackets, urethane bushings in the trailing arms and new s.s. nuts, bolts and lock washers. While everything was out I carefully checked to see if the differential mount was cracked in any way and I could neither see, or feel, anything amiss. Everything gets installed without problems. But I still have a knocking sound coming from the rear whenever I let out the clutch. Sometimes it's just solid knock; at others, it almost sounds like rocks being crushed.
I took it into Sears one afternoon after having a conversation with a couple of their mechanics, one can never be too careful these days. Anyways these guys did do their level best (and at no charge!) to find the knock. One guy sat in the car while it was on a lift and kept letting the clutch out while another poked around underneath trying to isolate the noise. Their conclusion was that the sound seemed to come from the differential, still. The differential unit itself was rock steady, so I'm confident it's not the dreaded broken pins. The other night I thought I heard what sounded like a u-joint going bad, it had that familiar squeak for a few seconds. Maybe the mechanic crushed a few roller bearings while replacing the u-joints. I know I'm missing a rubber packing piece from under one of the rear coils. That might cause some noise. I'm wondering if the adjustable mounting brackets could be a source of this knocking-I know one side of these brackets are designed to free float. Has anyone who has installed these noticed anything similar? Any other suggestions are greatly appreciated. I'm planning on spending another weekend under the car within the next few weeks and I'd like to have a game plan together.
 
Did the fellows at Sears check the differential with a mechanics stethoscope? One of these will help find the noise quickly, unless of course it is a u-joint.
I can't imagine the adjustable brackets being the problem unless they are loose.
Go through the entire rear end and check for loose fasteners.
While the rear end is in the air, check your half shafts for excessive play.
 
Also check ALL the flange bolts,& retorque them to specs.I'd replace ALL the bolts with SS. /ubbthreads/images/graemlins/thumbsup.gif /ubbthreads/images/graemlins/iagree.gif
 
Don't even think of using Stainless Steel in those fasteners. Suspension parts are stressed joints and SS bolts are only equivalent to grade 2, unhardened bolts. If you replace the bolts go with grade 8, and make sure that the unthreaded shank length is the same as on the original ones. If there are threads through the shear plane you are asking for a failure if the bolts are loaded in shear.
 
[ QUOTE ]
Don't even think of using Stainless Steel in those fasteners.

[/ QUOTE ]

/ubbthreads/images/graemlins/iagree.gif

[ QUOTE ]
....SS bolts are only equivalent to grade 2, unhardened bolts.

[/ QUOTE ]

Unless you get them at Home Depot, in which case they are grade 0 or worse.

/ubbthreads/images/graemlins/thirsty.gif
 
Thanks guys. The bolts themselves were supplied by a vendor for this specific application; only the nuts and washers were s.s. And the mechanics did not use a stethoscope while checking for the source. A previous post mentioned the possibility that the shocks could come loose over time. I'll check for that. Is it possible for the splines on the axle shafts to be worn to the point where they can cause a knocking sensation? They still appear crisp in detail, not rounded over at all. How about the hubs themselves? Do they make a knocking sound when they wear out? How would I check their condition? And the wierd thing is, sometimes there's no knock at all, although those times are few and far between. My current plan is to check the shocks for looseness, re-torque all fittings, remove the half-shafts and inspect u-joints (again), and replace rubber insulator under the one coil spring that is missing. I guess after all that, if it's still present, I need to contact the shop that re-built the diff.
 
I had aknock in my rear end on my TR3 that turned out to be a slightly loose shock that was banging up and down over bumps. It doesn't sound quite like your problem though.

How about the drive shaft U joints? Could you have something hanging up in the rear brakes? It doesn't sound like a center section to me. Rear end noises are always tough. Check the backlash in the diff., it might be set up too tight.
 
Sometimes it is so simple that you might overlook, how is your exhaust system setup. Can get some weird noises depending on what those hangers are doing.


Bill
 
The PO of my TR was so cheap he had the exhaust pipes,
muffler, etc welded to the frame instead of replacing
the worn out hangers.

I found out when I was trying to track down all the noises
coming from the cars tail end. Cost me $85 to have the
welds ground out and then $14 for real hangers to be
installed.

That cured ONE of the many noises from the tail end.

D
 
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