Rear suspension thuds & rear end swaying on new DD Mark

[Scallywag]

I welcome you! I need some help diagnosing some noise and traction control behavior I've been experiencing.

So, the daily driver BA went down for the count in Feb. after a frontal impact and I had to drive the K4 for a little bit until I bought a Whte Pearl(WF) to act as the new daily driver.

All is well save for the fact that all of a sudden just recently the suspension for the WF started acting too bouncy in the rear end when going over road imperfections, as if though it were on springs. I remember thinking to myself that it might be on some bogus coils instead of air because the rear would bounce for a pretty good while after driving over a bump. After about 2-3 weeks of this it stopped bouncing but has now developed a hard thud when driving over bumps, train track etc. If I were to guess I'd say it's almost as if the air strut is rebounding back up and hitting the under carriage hard, kind of thud. What would cause this? Strut mounts?

Incidently almost at the same time the bouncing-hard thud started did I also notice that the rear end would sway when going over the same pavement. If I'm driving straight and go over, lets say a sewer cap, not only will it thud hard but the rear end will sway for a split second to the direction of whatever tire went over the cap. Even less confident does it feel when the road is curved(like by O'Hare) and there's a lil hump that I drive over when going through the curve that immediately I'll feel the rear end wanting to go on its own way. Where could this stem from?

More than likely I'm wrong but I assume the 2 symptons are related since both surfaced at the same time and occur in tandem with each other.

Any ideas would be appreciated!

Spanks!

 

[soduka]

Your shock mount(s) in the trunk are probably disintegrated, letting the whole thing flop around back there. It's an integral design so you either need to cough up about $200 a shock for the specific Motorcraft shock unit if you can still find them or buy some Thunderbird/Cougar shocks for $20 each and then buy a retrofit mount kit from 98lincmk7lsc for about $60.

 

[Scallywag]

Thanks for the suggestion! A couple of weeks ago I read a topic on here about this issue when I investigated this after it first started happening that was eluding to the same point you're making. I just can't remember the search string I used that brought up that thread.....

In any event, do you know if they're difficult to remove and reinstall? I still have the BA at the garage with the K4 and can use the parts from the BA as I please.

This is new to me as all the work I've ever had to do on all my Marks so far has been on the front.

 

[PenGun]

You want to check the location plates for the IRS. They are basically where you jack up the rear end. When they rust out it gets wiggy back there.

 

[chris2523]

take a look at the rear "toe link compensators"



they help hold the toe of the rear control arms.
if yours look like the ones on the left, you might need new ones.

 

[Scallywag]

Your shock mount(s) in the trunk are probably disintegrated, letting the whole thing flop around back there. It's an integral design so you either need to cough up about $200 a shock for the specific Motorcraft shock unit if you can still find them or buy some Thunderbird/Cougar shocks for $20 each and then buy a retrofit mount kit from 98lincmk7lsc for about $60.

Well, I found a vendor on Amazon that's selling 3 Rear Shock Absorber Mounting Kits: F8LZ-18197-AA for $50 a piece. Do you think that the thumping can be remedied just by replacing the mounting hardware alone or might as well replace the shock while down there?

If I'm replacing everything, then RockAuto supposedly has 1 Motocraft "strut" available for $212.79. I find it odd that it is in the strut section instead of the shock absorber section that does list an Arnott alternate that is out of stock. I guess it doesn't matter.

Otherwise there is the Thunderbird shock absorber for $29.79 plus the mounting hardware from whoever I get it from. There are other companies offering their brand of rear gas(?) shocks and mounting hardware as well but I prefer original or from within the community if I can.

Maybe now would be a good time to sensor lower it as well....

 

[soduka]

That's because the airbag isn't "really" a shock like everyone thinks of traditional shocks. When you say shock to someone who would know what a car shock is, they think of the pressurized long tubes. The rear suspension of the Mark VIII has both a traditional shock and an inflatable air bag.

I don't know what the mounting kit is but I can assure you the only person in the world you can get the right thing from is 98lincmk7lsc, it's a custom job. Like I said the original design is integral, the original mount on top of the original shock was not designed to be replaceable separately from the shock itself. A few people have gotten creative in the past using a torch to melt the old bushings out and then hammer in new ones but honestly if they're the original shocks it's time for new ones anyway.

 

[Scallywag]

Just to share, this is how they look

Passenger




Driver




Obviously they look far worse on the outside.

Here's another mounting kit from ebay. But more than liekly I'll get the T-Bird strut/shock and Jays retrofit kit.

While down there, I think I spotted something that may contribute to the noise I've been hearing as of late.

Rear Driver


Rear Passenger


I could be mistaken, but I think that doohickey on the driver's side is supposed to go into that rack/bar/bracket thingymajig.....

 

[ervin]

yeah , you need upper shock mounts and sway bar end link bushings

 

[soduka]

Yeah, half the sway bar link missing might have something to do with it.

 

[98lincmk7lsc]

Scallywag, I've got the shock mounts in stock and ready to go. PM me if you'd like to order a set. Those stock ones are definitely shot! I would recommend installing new shocks at the same time. You can use any 89-97 Thunderbird shock, or any 99-04 (IRS-equipped) Cobra shock.

If you're looking for factory ride quality, I'd recommend the Monroe Sensatrac 5965, and for a more performance-oriented shock, I'd recommend the 03-04 Cobra Bilsteins. The Monroe's are also your most economical option and go for about $20 each on RockAuto.com.

The shock mounts are $66 shipped, and are 100% stainless steel construction, including all fasteners and washers, and include Energy Suspension poly bushings.

See pic below:

 

[Scallywag]

I'd more than happy to take a set since I'll be placing the order to RockAuto for the shocks and other stuff either today or tomorrow.

Just let me know to what paypal to make it out to.

Thanks!

 

[98lincmk7lsc]

I'd more than happy to take a set since I'll be placing the order to RockAuto for the shocks and other stuff either today or tomorrow.

Just let me know to what paypal to make it out to.

Thanks!

Sure. Jay.richmond(at)gmx.com

Let me know what shocks you'll be using since some of them need different sized washer/bushing holes.

 

[97 Octane]

Scallywag, if you plan to sensor lower your Mark and wanna use a shock that exhibits factory ride quality, order a set of Monroe Sensa-trac 5950. This shock is a perfect fit to Jay's stainless steel shock mounting kit above.

The 5950's have a 4" shorter compression length but it also extends slightly longer than factory shocks. It's perfect for sensor lowered Marks because, unlike the factory shock, you won't have to worry about bottoming out the shocks when running over a small rock or something.

oh yeah, don't forget to do a wheel alignment after sensor lowering your Mark.

 

[Scallywag]

Sure. Jay.richmond(at)gmx.com

Let me know what shocks you'll be using since some of them need different sized washer/bushing holes.

Yes sir !!! Payment already sent, hopefully to the right paypal.....

Those Cobras look sweet but, YIKES!, damn near $900!! Instinctively I wanted MOTORCRAFT but ended up going for the MONROEs as suggested and am in hopes that the new shocks & rear links will help eliminate that infernal rattling/thudding in the rear end.

Let me know if you got the credits.

 

[98lincmk7lsc]

Got it. I'm heading to the post office in just a minute.

 

[PenGun]

Sure. Jay.richmond(at)gmx.com

Let me know what shocks you'll be using since some of them need different sized washer/bushing holes.

I had to drill em' out to fit my Konis. No problem at all, I actually found a 31/64" bit.

 

[Scallywag]

These came in earlier in the week.



Very solid and sturdy feel !! I'm sure they'll do great once I receive the shocks, which I haven't just yet. I just hope it's as easy as it seems.

It appears all that is required is to unfasten the mounts from the trunk, remove the control arm bolt, compress the shock to remove it, and then reverse procedure to install.

I take it that I'd probably would have to bleed the rear bags to remove the shocks a lot easier. If so, do the rear bags have a release valve like the front bags? I scanned the bags last week when changing the rear sway links but couldn't see anything similiar to the front bags.

 

[98lincmk7lsc]

These came in earlier in the week.

View attachment 828473801

Very solid and sturdy feel !! I'm sure they'll do great once I receive the shocks, which I haven't just yet. I just hope it's as easy as it seems.

It appears all that is required is to unfasten the mounts from the trunk, remove the control arm bolt, compress the shock to remove it, and then reverse procedure to install.

I take it that I'd probably would have to bleed the rear bags to remove the shocks a lot easier. If so, do the rear bags have a release valve like the front bags? I scanned the bags last week when changing the rear sway links but couldn't see anything similiar to the front bags.

It's pretty easy. The last couple times I've replaced shocks on a Mark VIII, I didn't even jack the car up. You can do it with the car on the ground, if necessary. No need to vent off the air bags.

 

[Hoot Gibson]

PM email sent to Jay. Help, I need parts!