Write-Up: Rear Suspension Support Assembly (RSSA) Modification

for anyone who has eliminated or plans to eliminate the OEM auto adjust rear ride height,this mod is for you.Or in other words,if you have done away with the OEM ride height compressor and are running monroe or other manual inflatable shocks.
I still am not sure what the, REAR SUSPENSION SUPPORT ASSEMBLY, does.It does support all the suspension components,sway bar,control arms etc...But I feel its main purpose is to allow the RSSA to move up and down within an inch or two along the RSSA's great big huge and super soft bushings called the "forward mount bushing" in the FSM.

these bushings together weigh 5 lbs. jack car up and place two jack stands directly underneath the RSSA

let the weight of the car settle on the jackes.this will pin the RSSA against the body. This mod will effectively drop the rear of the car more than 3/4' or so,so if you are satisfied with your ride height cut the spacer(more on that later) so that the whole fabbed assembly is the same height as the stock FBM. After you're done,the RSSA has to be pushed up against the underside of the body nice and tight.If you have any clearance issues with the exhaust afterwards,you can use steel plate to shim up the RSSA.the plate will be flush against the body and not the RSSA.I had to move the exhaust over a bit to get it to clear the RSSA exhaust tunnel thats under the fuel tank.I rubbed a little bit.If there is any gap at all between the RSSA and the body,you have to fill up that space with metal shims.

First step is to find a couple extra front cradle (they fit perfect) insulator support cups.I got an extra set at the junk yard for 3 bucks..

thats not what they are called in the manual,I have not found a name at all! they are in the shape of a mushroom and the go on top of the front cradle insulator bushings.For this purpose Ill just call them cup washers. remove the support bracket,

it has the 3 15mm bolts,and remove the FBM,

now you will see the RSSA in all its confused glory.clean area real well with acetone,you will need to weld later on.

cut a 3/4 " spacer out of 1" tubing and place atop the upturned cup washer.

run a bolt through it,you will have to find a grade eight bolt identical to the OEM bolt just about an 1' shorter. now screw bolt with cup washer back into its place through the RSSA and into the body.

when the cup washer is snug and square and in place,run a weld around the outside of the cup washer welding it to the RSSA.

remove the bolt,place bracket ,hit it with a little paint for rust,and bolt the support bracket back in place.


This modification has allowed me to drift ever so nicely around any corner at will.it takes just a little getting used to.the rear end is nice and stiff now.The OEM FBM's allow way too much movement and imo is way dangerous for any spirited driving.Going around a corner with the OEM,the rear never gets down to the business of making the turn.At low speeds its not a problem but at higher speeds(you know who you are) she pushes way too much.this mod will allow YOU to control the car instead of GM doing all the work.

also note,that the beauty of this mod is that you can test it before you weld it.Just secure the cup bracket in place,maybe a tiny tack weld or some duct tape,replace cover and bolt and take her for a test ride.big difference!

I should mention,Once you are satisfied with the ride height of the RSSA,it WILL change your ride height,you should find 3" or 4" dia dom pipe or other,and cut a spacer out of it and then run down your bolt.When the OEM set up is at full sag,the space between the RSSA and the body is a little more or a tad less(depending on the age and particular wear of the OEM shocks air leaks etc.....

Here are a few pics of my modified RSSA. I was able to shave off close to 12 lbs with no loss of strength.The RSSA if you think about it is a real piece of very heavy redundancy added to an allready heavy car.I can guess the reasons why a luxury car woud have weight engineered into her,but I dont buy into that.The car has not suffered at all with my mods.If anything she takes off like a rocket now and corners well enough to scare me without scaring herself.awsome.



as you can see its way over built.



gave her a nice haircut



plate welded onto it





By the way the RSSA is attached to the underside,the piece flexing is near impossible.next order of business is to eliminate alltogether the RSSA and have the control arms individually mounted to the underbody.will not be easy but this will drop another 45 lbs off the back.

I think you're right about the newer cradles being much smaller now that I look at your pics of the cradle out and cut. As soon as I can work out a way to receive it from freight, I'm feeling inspired to order the lucerne cradle from morad. It looks like it's definitely lighter. I can tell there are definitely some differences between the cradles but not that cannot be dealt with within reason.
Did you take a stock weigh of it?

57 lbs

Hey Robo, I have a lot of flopping around in the back of my riv, even with new shocks its all bouncing around. I am suspecting that my RSSA is moving too much(possibly worn out stock mounts) Would it be possible to replace these mounts with hockey pucks? also Did you hard mount the mounts in the back of the RSSA as well where the your rear adjustment links attach?

robotennis61 wrote:

57 lbs

Thinking about it the RSSA probably weighs as much as it does to help with F/R weight distribution for ride quality reasons. Depending on what you call "ride quality" I guess.

@ Greg-I'm not too sure about the OEM style shocks.I had a love /hate thing going on there.I prefer my Bilsteins.As far as the RSSA is concerned,That hunk of steel moves alot! The ultra soft forward mount bushings are really flexible and mushy.This ensures a quiet and isolated ride.Exactly what GM wanted to give the typical Riv buyer.Those, along with the really soft series 1 control arm bushings & the mushy rear mount bushings and you got a cushy ass ride.Not for me.Idealy I would want to be in control.The RSSA makes it difficult to control the ride.Just my opinion.
The hockey pucks wont work in place of the forward mount bushings.The ID of the bushing mount location is larger than a puck.I tried it.Made myself feel right stupid too! Only way I could figure out is to do what I did.I'm sure there are other ways,this was the only thing that made sense to me.

@ AJ -I dont know? I must have shaved off in total at least 25 pounds.I can now swing the Rivs ass around anytime I want.I like that.

Interesting, I'll have to look into my options, so what did you do to stiffen up the rear mount bushings for the RSSA? Your car must handle like a fricken race car with all of your suspension mods! I'm still waiting on my rear sway bar.

robotennis61 wrote:

@ Greg-I'm not too sure about the OEM style shocks.I had a love /hate thing going on there.I prefer my Bilsteins.As far as the RSSA is concerned,That hunk of steel moves alot! The ultra soft forward mount bushings are really flexible and mushy.This ensures a quiet and isolated ride.Exactly what GM wanted to give the typical Riv buyer.Those, along with the really soft series 1 control arm bushings & the mushy rear mount bushings and you got a cushy ass ride.Not for me.Idealy I would want to be in control.The RSSA makes it difficult to control the ride.Just my opinion.
The hockey pucks wont work in place of the forward mount bushings.The ID of the bushing mount location is larger than a puck.I tried it.Made myself feel right stupid too! Only way I could figure out is to do what I did.I'm sure there are other ways,this was the only thing that made sense to me.

@ AJ -I dont know? I must have shaved off in total at least 25 pounds.I can now swing the Rivs ass around anytime I want.I like that.

@ Robo: For a car to swing around... you would have liked the old Dodge Shadow/Plymouth Sundance (Duster), which had something like a 70/30 F/R weight distribution when you put a 3.0L engine in - it was a very large lump for that car.

Has anyone other than Robo done this? Is anyone here crazier than Robo?

charlieRobinson wrote:

Has anyone other than Robo done this? Is anyone here crazier than Robo?

I dont know? Turtle went so far as to order the adjustable links but I dont know if he hard mounted them yet or modified the RSSA.
Anybody nuttier than me?Nope.I am the mercury in the vein that makes the Hatter mad.

Robo, if I'm understanding you correctly you just replaced the two rubber bushings (what the red arrows are pointing to in the picture below) with the cup washers used on the engine cradle? Can you make a little diagram of how you placed everything? Bottom of the body > cup washer > bracket is how I think you did it but I may be completely wrong.



If you look closely in the exact middle of the picture you'll see a tiny baby frog (toad?) on the driveway 

Wow,it's complicated.Been Did it a long time ago.
If you can get 2 threaded steel plates,threaded to match the 2 long OEM bolts of the RSSA in the pic,and weld them directly to the chassis and just ditch the OEM rubber bushing thingies and mount the RSSA directly to the chassis,you will have your super modded RSSA.Makes all the difference in the world.
All you'll be doing is hard mounting the RSSA to the chassis.Figure out how to mount the RSSA without the bushings and you got it.Just take the rubber bushings out of the equation
After figuring all this out,go for the alu threaded tie rods that I came up with and the improved handling of the Riv will blow you away.

robotennis61 wrote:

After figuring all this out,go for the alu threaded tie rods that I came up with and the improved handling of the Riv will blow you away.

I was thinking about doing that but I'm just not sure of how you mounted them to the RSSA. I saw turtle used custom spacers which seems to be the ideal way but if you could elaborate on that it would help a lot.

Ya know,I bet I can't remember half of the stuff I did to make it work.Just order the Alu rods and all the accompanying hardware,crawl under there,take shit apart and figure it out.that's what I did.Really,I wouldn't know how to put it in words any differently than I did in my above posts

Alright I took the rear tire off and I think I'm going to go about it a different way. Instead of welding things and getting different sized bolts I'm just going to get a couple nice thick washers the same thickness as the bushing and simply swap them in. That way there's no air gap at all like there is with the cup washers.

Ok but,when you take it apart you will wind up with 2 big holes where the RSSA bushings were.You have to use thick 1/4" steel plate or the mushroom washers to fill it in.
When it's all apart,remove the bushings and place a jack under the RSSA and jack it up.You will then notice that the RSSA frame touches the chassis before the RSSA mounting points do,you will then realize that the mounting points have to fit against the chassis FirsT!At this point you will see the wisdom of filling in the RSSA holes left by removing the bushings.The fat washers are a great idea tho.
Start the project and everything will then become very clear to you.You will see the gap.You will see the need for the steel plate or hunt around for the mushroom washers,those are the best and really fit the project.And be prepared to cut the OEM bolt by at least an inch or two,if not they will try to punch thru into the underside of the car and into the area under the back seat.Not a disaster but ugly and close to the Rivs sensitive electronics and wire loom.
The hardest part is getting around your brains natural desire to protect itself and discourage you from starting the mod in the first place.Once there you will see how plain simple stupid the mod actually is.
Keep me posted

For the sake of clarity, this mod changes the ride from soft to stiff, right?

robotennis61, are you still around?