One of two things I am thinking of...
1. Differential is out of oil/dirty oil... I've had one on a car I was
towing that was empty and it made a loud noise like what you are describing and
started locking up. Filled with oil and it quieted down nicely... just don't
think I'll be using that particular diff in a running car though.. You might
want to check that fluid and change it anyway...
2. Wheel bearing is going out. That makes the same loud rumbly noise. You
can test them by jacking the car up and trying to move the wheel... if you can
see the axle move in relation to the diff housing, you have a bad bearing.
You may see some oil leakage from a bad wheel bearing because it elongates the
seal I think it's about $140 for the bearings and seals, plus the work to
press off the old collar and put all new stuff on.
Good luck!!
Eric
>
> From: "Matthew Smith" <matthews517@earthlink.net>
> Date: 2005/11/01 Tue PM 06:59:57 EST
> To: <datsun-roadsters@autox.team.net>
> Subject: The first of a several questions
>
> Hi All,
>
> I have now had my drivers license back for a week, and am finding MANY new
> things I need to ask. The first of which is a VERY scary noise coming from
> the rear of my car.
>
> Loreli has developed a (potentially) horrible noise from the rear end. This
> usually happens in 3rd, 4th, and 5th gear. At first, I thought it was just
> back-rap from the header/exhaust. It seems that when moving in gear, under a
> reduced power, as in slowing down or going downhill with my foot off of or
> lighter on the gas, I hear a rumbley noise from the back of the car. I
> noticed this first when driving from Chattanooga to Nashville this weekend.
> I did have the car well over the speed limit a couple of times on this 2 =
> hour run. (110 at one point). My first thought was the normal back-rap from
> a semi free running exhaust on a standard transmission. This doesnt seem to
> be it. When I backed out of my parking spot at Starbucks, I heard a TERRIBLE
> grinding noise from the rear end. Bad enough that I had to stop and jump out
> to see what was wrong. (at the same time I got into a great conversation
> with a Gentleman from Nashville who once had a 66 1600 that he bought from a
> friend who was a Datsun dealer in Nashville. They flew the dealers private
> plane to New Orleans to pick the car up directly from the ship from Japan).
>
> Tomorrow I plan to take Loreli to the lube shop to check the oil in the rear
> end, but I wondered if anyone else has heard this very expensive sounding
> noise. I grabbed the drive shaft (not an easy feat for a guy over 275
> pounds) and wiggled it. Doesnt seem to be u-joints, but there is a fair
> amount of play in the driveshaft. (probably more than an 1/8th of an inch in
> each direction. Any ideas?
>
>
>
> Matthew A. Smith
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