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1970 DeVille rear differential oil

Started by stushug, August 13, 2022, 07:02:17 PM

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stushug

I just replaced the leaky pinion seal on my DeVille. While the old one was out, a good deal of the fluid drained out. I've decided to drain the remainder and replace with new oil. I'm not sure what weight and if I'll need any additives. Any help is appreciated! Thanks.

Dave Shepherd


stushug

I'm not sure. What's the simplest, surest way to confirm whether mine  is posi  or not? I haven't messed with a diff in a long time.

Dave Shepherd

To be sure you would jack up the rear axle, both wheels off the ground, front wheels safely blocked,, car in neutral, if you rotate one wheel, the other would turn in the same direction, if it doesn't,  it is a std open diffferential.

Cape Cod Fleetwood

If your car has posi-trac Michael used Valvoline full synthetic 75w-90
Use a cork gasket.
There are 2 kinds of cars in the world, Cadillac and everything else....

The Present -1970 Fleetwood Brougham

The Past -
1996 Deville Concours
1987 Sedan De Ville "Commonwealth Edition"
1981 Coupe De Ville (8-6-4)
1976 Sedan De Ville
1975 Sedan De Ville

The Daily Driver and work slave -
2008 GMC Acadia SLT *options/all

stushug

Thanks for the info, I'll be checking it very soon.

stushug

When I spin one of the rear wheels, the other wheel spins in the opposite direction. This happens from either side. Is this open or posi?

The Tassie Devil(le)

'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

35-709

Over the pinion flange you will see a single number stamped into the housing which is the code number for the axle ratio --- IF that number is preceded by the letter "G", you have a controlled differential (posi-traction in Chevrolet speak).  It is all in the, easy-to-find-on-eBay, Cadillac Shop Manual.   As Bruce said, you have an open differential.
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

stushug

#9
I finally finished sandblasting, painting and re-installing the differential. I drained the old diff fluid and replaced the gasket on the rear cover. I replaced the steel line brake line that runs from the engine bay to the rear brake hose. Replaced the old brake hose. The new one is about 1 1/4" shorter so I lengthened the bracket that holds it by 1 1/2" so it could reach the mounting bolt on the diff. I also installed new steel brake lines that run along the diff to each wheel cylinder. Installed the new gear oil, replaced the old wheel cylinders, brake shoes, hardware, star-wheel adjusters and out of round brake drums. Also installed new coil springs and shocks. What a difference visually, and mechanically. I'm attaching some pics for reference. 20220816_153143.jpg20220904_185919.jpg20220811_111200.jpg20220924_131240.jpg20220924_145606.jpg20220918_110636.jpg20220918_161936.jpg         


stushug


klinebau

The correct length rear brake hose is available.  On rockauto, you can find it for the 1970 Buick Electra.  I have purchased and compared it to the original hose and it is a perfect match.  I don't know why it isn't listed for the 1970 Cadillac Deville, but I guess there is a mistake in the parts catalog that will never get corrected.
1970 Cadillac Deville Convertible
Detroit, MI