Subject: Re: [Spits] Rear End Noise.... dumb question

From: Doug Braun <[email-masked]>
Date: Mon, 14 Jul 2014 12:44:59 -0400

Is this a single or erratic knock, or a continuous knock-knock-knock-knock?

Here is one way to test those U-joints:

Put the car in neutral and cost at about 25 MPG.  Do some reasonably quick
S-turns,
zig-zagging back and forth.  If the knock-knock-knock appears as you turn,
but not as you are going
straight, it could be the U-jonts.

Once I had an erratic knock back there, and it turned out to be that the
eye had broken off of one end of a rear
shock, and the end of the shock was smashing against the mounting stud
every time I went over a bump.
This was a bummer, since the car still had the original DeCarbon shocks,
which had been in perfect working order.
I tried a couple of different types of replacements, but the originals were
better than any of them.

Doug

On Mon, Jul 14, 2014 at 12:30 PM, Jim Cullen <[email-masked]> wrote:

> Hi listers.....
>
> I wonder if I could get some insight/advice on a knocking noise that seems
> to
> be coming from the RH side of my rear end. I notice it more @ once I get
> up to
> about 50 km/hr, especially over bumps (to the point I thought it was the
> shock
> absorber and replaced that to see if it disappears as it seemed to sound
> like
> the shock absorber was b bottoming outb b  unfortunately, no joy there),
> and when making left turns.
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From: "Bill Gingerich" <[email-masked]>
Date: Mon, 14 Jul 2014 11:55:28 -0500

Jim,

I've noticed the same type of "one wheel turns" situation on several cars.
To my understanding, it is normal.  It has to do with the ability of the
diff to allow the axles to turn at slightly different speeds as you turn a
corner.  I don't recall the specific mechanics that go on, but I wouldn't
worry about it.  My "unlimited slip" '99 F150 does the same thing.

Sorry, can't help you with the u joint question.

BillG
'74 Spit

-----Original Message-----
From: Spitfires [mailto:[email-masked]] On Behalf Of Jim
Cullen
Sent: Monday, July 14, 2014 11:30 AM
To: [email-masked]
Subject: [Spits] Rear End Noise.... dumb question

Hi listers.....

I wonder if I could get some insight/advice on a knocking noise that seems
to be coming from the RH side of my rear end. I notice it more @ once I get
up to about 50 km/hr, especially over bumps (to the point I thought it was
the shock absorber and replaced that to see if it disappears as it seemed to
sound like the shock absorber was bbottoming outbb unfortunately, no joy
there), and when making left turns. After doing some research (see link b
http://www.britishcarforum.com/bcf/archive/index.php/t-28039.html) I thought
it might be the uv joint for the RH driveshaft (note that these were
replaced relatively recently, but from reading the experiences of others the
relative bnewnessb of the driveshaft may not preclude the uv joints of the
driveshaft from being the culprit).

I have the car now jacked up and have done an inspection of the uv joints. I
donbt see any evidence of play in the uv joint and the circlips on the
joint appear tight. Is there a better way to diagnosis the uv joints a
possible issue? I thought I should check the propshaft uv joint too, but
this seems okay too.

Here is my dumb  question, with the car jacked up and in neutral when I hand
turn the prop shaft I note the LH side drive turns in unison with the
propshaft, but the RH side doesnbt (it lags or doesnbt turn). I know I
should know if this is an issue, but despite having this car for close to 20
years and doing most of the work on it myself (as well as being an eager,
but novice mechanic) I essentially know very little about the differential
(other than what I learned from the Haynes manual and from when I replaced
the driveshafts a year and a half ago). So, my dumb question is two
part..... is what I bdescribedb normal? if no.... could it be the source
of my rear end noise (differential needs to be replaced)? I hesitate to name
the differential as the culprit, because most of my research seems to
suggest differentialbs donbt knock like mine is (they bwhine), but given
my novice intelligence about differentialbs Ibm not really sure. Anyhow, I
would appreciate some insight

Thanks for the help,

Jim Cullen
1974 Spitfire

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From: [email-masked]
Date: Mon, 14 Jul 2014 13:35:23 -0400

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From: "Quirk" <[email-masked]>
Date: Mon, 14 Jul 2014 12:04:36 -0600

Hi Jim,

Google "spider gears" view associated pictures and you will see why one
wheel turns and the other doesn't.  It is that cluster of four gears that
allows for a difference in speed between the rear wheels as you turn corners
or loose traction and spin one of the rear tires.

With respect to your knock if it is irregular and happens over bumps etc.,
it could be from anything that moves with or comes in contact with the
suspension.  If it is regular and occurs at the same frequency as wheel
rotation it should be in the driveline between the differential and the
wheel rim.  If it is regular and occurs about 4 times each wheel revolution
then it is in the driveline from the differential forward to the
transmission.

....Spitman....

-----Original Message-----
From: Spitfires [mailto:[email-masked]] On Behalf Of Jim
Cullen
Sent: Monday, July 14, 2014 10:30 AM
To: [email-masked]
Subject: [Spits] Rear End Noise.... dumb question

Hi listers.....

Thanks for the help,

Jim Cullen
1974 Spitfire

[email-masked]
Archive: http://www.team.net/archive
http://autox.team.net/mailman/options/spitfires/[email-masked]

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From: Doug Braun <[email-masked]>
Date: Mon, 14 Jul 2014 15:50:07 -0400

If you have a driveshaft problem, such as a bad U-Joint, it will often show
up as
an obvious nasty vibration round 50 MPH.

[email-masked]

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From: Doug Braun <[email-masked]>
Date: Mon, 14 Jul 2014 15:51:42 -0400

Don't forget to check that all the nuts and bolts that hold the three
U-joint flanges to the differential are tight!

Doug

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From: [email-masked]
Date: Tue, 15 Jul 2014 06:37:45 -0000

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From: [email-masked]
Date: Tue, 15 Jul 2014 06:45:44 -0000

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From: Donald H Locker <[email-masked]>
Date: Tue, 15 Jul 2014 10:56:27 +0000 (UTC)

Besides checking what others have recommended, also check that the trailing link is secure at both ends and that the body where the link attaches is not cracked. (Don't ask how I know.) This can cause a knocking sound whenever you hit a bump or when powering up or down.

The diff behaviour sounds normal. If the prop shaft is prevented from turning, the wheels will turn in opposite directions from each other. (Turn one forward one turn, the other will turn backward one turn.)

Donald.

----- Original Message -----
> From: "Jim Cullen" <[email-masked]>
> Sent: Monday, July 14, 2014 12:30:04 PM
> I wonder if I could get some insight/advice on a knocking noise that seems to
> be coming from the RH side of my rear end. I notice it more @ once I get up
> to
> absorber and replaced that to see if it disappears as it seemed to sound like
> the shock absorber was bbottoming outbb unfortunately, no joy there),
> and when making left turns. After doing some research (see link b
> it might be the uv joint for the RH driveshaft (note that these were replaced
> relatively recently, but from reading the experiences of others the relative
> bnewnessb of the driveshaft may not preclude the uv joints of the
> donbt see any evidence of play in the uv joint and the circlips on the joint
> appear tight. Is there a better way to diagnosis the uv joints a possible
> issue? I thought I should check the propshaft uv joint too, but this seems
> okay too.
> 
> years and doing most of the work on it myself (as well as being an eager, but
> novice mechanic) I essentially know very little about the differential (other
> than what I learned from the Haynes manual and from when I replaced the
> driveshafts a year and a half ago). So, my dumb question is two part..... is
> what I bdescribedb normal? if no.... could it be the source of my rear end
> noise (differential needs to be replaced)? I hesitate to name the
> differential
> as the culprit, because most of my research seems to suggest differentialbs
> donbt knock like mine is (they bwhine), but given my novice intelligence
> about differentialbs Ibm not really sure. Anyhow, I would appreciate some
> insight
> 
> Thanks for the help,
> 
> Jim Cullen
> 1974 Spitfire
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