IML: Differential Failure/Long Read

[randalpark@xxxxxxx]

Now just a second...these never wear out??? We are talking about cars 
that are over 40 years old, mostly with a questionable past. If nothing 
else, sitting around too much damages things almost as badly as driving 
them into the ground. Obviously, the best mix for long life is 
occasional and careful use with lots of ongoing maintenance and repairs.

Differential trouble is not uncommon. Having one rebuilt is no 
guarantee that it won't give trouble again, and it will give trouble 
again quickly if the person/shop doing the work doesn't do it right. 
Also, a lot depends on the type of use and maintenance the car had when 
it was driven the first 100,000 miles. Jack rabbit starts, overloading, 
and sudden grabs between the rear wheels and pavement, such as those 
experienced when accelerating over a wet crosswalk, are hard on the 
entire drive train, but particularly so on the rear axles and often the 
differential. Of course, failing pinion seals, and slow leaks without 
fluid replenishment is another common problem.

I drove used various Imperial's as everyday cars from 1968 through 
1985. I was usually at least conscientious about the way that I drove 
and maintained them. I experienced pinion bearing failure in four out 
of six cars. Plus, since then in a Ford and a Buick as well. The Buick 
only had 80,000 miles on it and never pulled anything. In the 
Imperials, it happened at high mileage and mostly to cars that had been 
used to pull vacation trailers in their past life. The differential in 
the '65 Crown failed at around 180,000 miles to the best of my 
knowledge. In this car, the symptoms were always there, a slight 
whirring on coast, and a noticeable delay, or slop, in the drive train 
between coast and acceleration, a sensation like the rear had to catch 
up to the front, while things felt totally normal from a stop. That car 
acted like this for many years and about 90,000 miles before the 
differential failed. Failure was quite sudden, first a loud clunk from 
the rear and then continuous grinding. It was tough finding a decent 
repair man at the time, but lucked out and found a guy who specialized 
in differential rebuilding in his own garage. He was expensive, very 
good, and had lots of spare parts.

Other failures were less dramatic, mainly just pinion bearings growing 
louder over time, until suddenly noticing that "gee this car used to be 
a lot quieter than that!" Again, I was driving these cars nearly 
everyday, with the radio blasting. The '56 suddenly "blew" at slow 
speed during an automatic shift from second the third gear. A sudden 
bang and the car coasted to a stop. That one had to be replaced and was 
not rebuild able as the case was cracked.

The car I drive everyday is a '80 FMC with nearly 400,000 miles on it. 
The only thing that had not been rebuilt to date is the differential. I 
had decided about 15 years ago that it was whirring on acceleration and 
planned to have it replaced as a preventive measure. The Lincoln dealer 
suggested leaving it alone until it got worse, and it never did. One 
day I am sure it will, as I have gone through this several times in the 
past. In the Seattle area, Dean Transmission has been a reliable place 
to have the work done correctly.

Paul W.


-----Original Message-----
From: DickB@xxxxxxxxx
To: mailing-list@xxxxxxxxxxxxxxxx
Sent: Tue, 23 Jan 2007 8:22 PM
Subject: Re: IML: rear end noise

I doubt the oil will have any effect on the noise. If you were having 
trouble with the limitted slip feature, I'd say to try changing the 
fluid, but the pinion bearing relies only on the proper adjustment and 
adequate lubrication - so I don't think that is the answer for you. Of 
course it couldn't hurt anything if you want to try.

I don't know where to obtain the right lubricant, but I suspect any 
auto parts store will have it. If you want to be sure to get the right 
stuff, order it by MOPAR part number - the number should be in your 
shop manual under lubricants - look in the rear axle chapter.

The fact that this is a repeat problem with the unit suggests that you 
would be wiser to simply replace the center section of the axle - 
contact one of the used parts vendors on the IML list for a quote. 
These just about NEVER wear out, I would not be at all afraid to buy a 
used unit, so long as it is full of grease and never rusted. You may 
not find another limitted slip unit, but I doubt that is important to 
you - it makes no difference unless you are into drag racing, or drive 
in slippery conditions a lot.

Dick Benjamin

----- Original Message ----- From: "Chris Strohmeyer" 
<chrisstroh@xxxxxxxxxxx>
To: <mailing-list@xxxxxxxxxxxxxxxx>
Sent: Tuesday, January 23, 2007 7:11 PM
Subject: Re: IML: rear end noise

> Thx all,
>
> Dick, this only has 10k miles on itbefore it was rebuilt with a noise 
> complaint by the previous owner. I've only had the car running for 
about > 300 miles. I wonder if I should drain the rear end and fill it 
with this > special fluid? My manual says to do this and drive at least 
100 miles to > see if the noise goes away. I wonder if this would make 
a difference and > whether the "mechanic" might of filled the rear end 
with 90 w gear lube?
> Where can I get this special fluid?
>
> Thx,
>
> Chris
> 67 Imperial
> ----- Original Message ----- > From: "Dick Benjamin" 
<DickB@xxxxxxxxx>
> To: <mailing-list@xxxxxxxxxxxxxxxx>
> Sent: Tuesday, January 23, 2007 9:47 AM
> Subject: Re: IML: rear end noise
>
>
> > This symptom is indicative of a worn pinion bearing .
> >
> > Sure grip rear axles do require special lubricant, it is not normal 
rear >> axle lubricant. However, I doubt the small amount you added 
would >> contribute to a pinion bearing problem. If the grease level 
was really >> low, however, you could have starved the bearing for oil. 
If the "top up" >> took less than a pint or so, I don't think that 
would have caused the >> problem.
> > You need to take the car to a differential expert and have it 
evaluated.
> > Dick Benjamin
> >
> >
> > ----- Original Message ----- >> From: "Chris Strohmeyer" 
<chrisstroh@xxxxxxxxxxx>
> > To: <mailing-list@xxxxxxxxxxxxxxxx>
> > Sent: Tuesday, January 23, 2007 9:23 AM
> > Subject: IML: rear end noise
> >
> >
> > > Hi all,
> > > My sure grip rear end is moaning/whirring at above 30mph. If I lift 
my >>> foot slightly off the pedal it goes away completely. After 
looking over >>> 40 years of receipts I discovered 10 years ago and 10k 
miles ago the >>> rear end was completely rebuilt. I read that there's 
a "special oil for >>> sure grips". Isn't this just 90w gear oil? It 
was a little low so I >>> topped it up but no change.
> > > Any ideas as to what this may be. I'm going to contact the former 
owner >>> to see if rebuilding it actually made the noise go away.
> > > Thx,
> > > Chris
> > > 67 Imperial Convertible
> > >
> > >
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