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1977 Fleetwood Rear Suspension

Started by Dan LeBlanc, May 09, 2019, 09:28:05 PM

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Dan LeBlanc

After seeing other tri-7s over the weekend, it appears to be sitting normally. Should be fine.

Dan LeBlanc
1977 Lincoln Continental Town Car

Series75

Air shocks are inexpensive, deliver a proper ride height and drive out right.  So why not go old school, bypass the leveling system, route the 2 Lines to a tee and install the fill valve behind the rear license plate.  These factory leveling systems blow.  Hate them.  I reworked the 66 and the 99 Fleetwoods with delco aftermarket systems.  The 66 is a vacuum system the 99 has an electric pump now in the trunk with a glove box remote control.  Think delco "jac pak".   Tom CLC 6866

The Tassie Devil(le)

The biggest problem with the single-fill air shocks, or any single-fill air suspension is that unless one installs a stop valve in the fill line, and activate it after filling, then as one goes around corners, the pressurised air from the outside shock will transfer to the inside shock, thus increasing the lean of the body.

Would be nice if there was a way of transferring the air to the outside shock to assist in leveling out the vehicle as it traverses the corner.

Bruce. >:D
'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

Glen

#23
Quote from: The Tassie Devil(le) on May 23, 2019, 10:12:01 PM
The biggest problem with the single-fill air shocks, or any single-fill air suspension is that unless one installs a stop valve in the fill line, and activate it after filling, then as one goes around corners, the pressurised air from the outside shock will transfer to the inside shock, thus increasing the lean of the body.
Bruce. >:D

Is that really a problem?  The hose that feed the shocks is 1/8th  OD.  The ID is a lot smaller.  I would think that you would have to be in a hard turn for a long time for this to be a problem. 
Glen Houlton CLC #727 
CLCMRC benefactor #104

The Tassie Devil(le)

It is a problem down here where I live, the place of mountainous winding roads, a bit like Hawaii.

But, you would be surprised just how much air would travel from side to side to create an imbalance.

Some people slow down when rounding corners, but not me.   I love to "drive" around corners.

Bruce. >:D
'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

Eric DeVirgilis CLC# 8621

Quote from: The Tassie Devil(le) on May 23, 2019, 10:12:01 PM


Would be nice if there was a way of transferring the air to the outside shock to assist in leveling out the vehicle as it traverses the corner.



You exactly hit on what Cadillac addressed many years ago. On OEM air shocks (when equipped with Level Ride), the air line feeds only one shock; from there, another line runs from that shock to the other thus maintaining equal pressure between the two rear shocks at all times.
A Cadillac Motorcar is a Possession for which there is no Acceptable Substitute

The Tassie Devil(le)

I agree, but when the centrifugal force of a vehicle going around a corner causes the outside of the vehicle to "drop" down, and the opposite side of the car rises, raising the length of the Shocker, this creates a lesser pressure within, and the air from the compressed shocker equalises to the other side, encouraging the increase of the roll of the vehicle as it traverses the corner.

In the case of a Roundabout, where the vehicle is cornering for an extended period of time, the air transfer is greater.

Bruce. >:D

PS.  Yes, we have roundabouts in Australia.
'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

Series75

Really important points when Dan is headed thru the S curves at Limerock park at 82mph, getting around town, maybe not.   Tom CLC 6866

Dan LeBlanc

anybody who's seen me drive an old Cadillac knows I'm not giving it all she's got in the turns (and on the straightaways too).
Dan LeBlanc
1977 Lincoln Continental Town Car

maximln

Quote from: Dan LeBlanc on May 21, 2019, 09:18:07 AM
Just to shed a little more light on the situation - sorry, I haven't been around much lately.

When the car was gone through before I got it, a rebuild level control valve was installed in the rear with a new set of AC Delco air shocks.  Upon removing the air shocks, I found them to be completely deflated.  Since AC Delco recommends a minimum 25psi for the shock to operate, that could have been an issue.  I noticed the car sits slightly higher than before.  I haven't driven it yet because I was busy preparing for the trip we just got back from.  Road test will be later this week to see how it rides with the current springs.  I rarely have back seat passengers, never jam pack the trunk, nor do I tow a trailer, so it may be fine for the interim.

One odd thing is, I can completely extend and retract the shocks out of the car.  That leads me to believe that the shock may have been too long.  The system must have been pressurized at one point if the suspension worked properly.

I may send out the vacuum compressor and get it rebuilt if I can find someone knowledgeable.  Jury is still out on that.

The compressor is very easy to rebuild.  There are usually only 2 parts that fail.  The piston & the rubber diaphragm.  The piston gets worn out & the diaphragm will get a tear in the rubber & leak.  I'm sure the biggest problem is being able to find those parts somewhere.

Max
2016 XTS Platinum
2008 STS Platinum
2006 STS
1998 STS
1993 STS
1990 Deville
1984 Cimarron
1975 Deville d'Elegance

Dan LeBlanc

I had the car out on Saturday, finally.  Put more miles on it in one day than it got in the last 5 years.  Rode just fine with conventional shocks.
Dan LeBlanc
1977 Lincoln Continental Town Car

Scot Minesinger

Dan,

That is how I would do it.  Many rave about their 1977, 78 and 79 large RWD Cadillacs (and they should) most of which are equipped without ALC.  Back in the 1960 and 70's it was not uncommon to see the family sedan driving down the highway with too much stuff in the trunk and the rear end sagging, hence ALC cured that.  Collector cars are not driven that way today, so in the RWD cars ALC is not essential.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Eric DeVirgilis CLC# 8621

#32
To this day I've never seen in person a 1977 DeVille equipped with Level Ride (standard on Brougham, Eldorado, Seville & Limousine) which was also the last year for the vacuum system. Seen a few DeVilles so equipped from 1978 & up but I would guess the number was far less than 50%.

Level Ride became standard on DeVilles in 1984.
A Cadillac Motorcar is a Possession for which there is no Acceptable Substitute

TJ Hopland

When I was shopping for and messing around with 77-79's I would say more than half of them I saw had ALC.  Out of maybe 30 cars that had it none of them worked.  If it was the vac system it appeared to be the compressor that wasn't working.  If it was the electric it seemed to be the control module that wasn't working.   I was not looking for higher end cars, if I had been maybe I would have found some that worked.

So how did this magic factory valve thing worked that kept the air from moving side to side?   They had to be passive, no electrical modules or sensors were involved.  They could not have been check valves because there was only single lines involved and the air had to be able to move both directions depending on what the main level control valve was wanting them to do. 

I once worked on a car where the guy had it set up with solenoids and switches to isolate things or combine things as needed which I thought was cool and was planning on doing it to my cars but I could not tell any difference with the sides connected or not connected so I didn't bother. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Eric DeVirgilis CLC# 8621

Quote from: TJ Hopland on May 27, 2019, 12:08:27 PM
When I was shopping for and messing around with 77-79's I would say more than half of them I saw had ALC. 

Level Ride was standard on all models except DeVille (and Cimarron) 77-83.

On 77-79 DeVille I have never found Level Ride to be a common option.

A Cadillac Motorcar is a Possession for which there is no Acceptable Substitute

Dan LeBlanc

#35
I can see the ALC as potentially more trouble than it's worth.  The only part of the equation on my car that had not been touched was the compressor.  Of course, that's what failed.

As I mentioned, the springs that were on the car when I got it (could be factory) with conventional gas charged shocks gave an acceptable Cadillac ride and upon filling the fuel tank, there wasn't much of an appreciable drop in the rear end.

Boy the car ran great though.  I understand why there was a Super Snooper K-band radar detector installed on this car when new - they do creep away on you.  Our local highway speed limit is 70 and looked down a couple times and saw that I crossed the 80 mark.  People were definitely looking - must be the triple black!

One more thing to do before summer - that's isolate a wind leak around the rear door.  I think it's the seal between the operable and fixed window.  The plastic trim seems loose and sounds like it's acting like a wind scoop and admitting air between the window frame and glass.
Dan LeBlanc
1977 Lincoln Continental Town Car

Scot Minesinger

More trouble than it is worth is exactly right IMO.

Glad you are enjoying your Cadillac now!
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty