[Guest]

I've been pondering this one for a while. Here's the scenario:

Every time I hit a bump while cornering at highway speeds, the rear end "hops" out a little. It is really noticable when you hit an expansion joint while whipping around a tight turn on an elevated ramp. It's a little unnerving to suddenly feel the @ss end shift about 6 inches towards the outside of the turn. Doesn't matter if I have a full or partial tank of gas back there.

The front end feels nice and tight, and doesn't move at all. It's only the rear that's having trouble.

Here's the current set up for my car's suspension: Bilstein 1516/1517 shocks, Moog Problem Solver idler arm, everything else stock. I am unfortunately still running the BFG Comp T/As - patiently waiting for them to finally wear out.

I'm curious as to what mods will help keep the rear end planted better in turns. I am hoping to have Bridgestone Potenzas by next spring. Perhaps this would help? Other future upgrades (as soon as the money tree in my back yard begins to bloom) include:

-body bushings;
-LCAs;
-aftermarket swaybars...leaning towards the Hotchkis setup;
-maybe stiffer springs...I'll see when I get that far.

I suppose an independent rear suspension would do the trick, but I'm sure there's a better way to address this problem.

As always, any insight is much appreciated! Thanks!

 

[Guest]

Paul,

As you are probably already aware, the stock rear 4 link really isn't the best setup, however it can be improved. The design of our rear suspension utilizes four links with two lower arms running paralell to the frame rails and two upper arms running diagonal from the pumkin out. The idea is to have full range of motions with limited side to side thanks to the diagonal upper arms. However, the weak factory parts just aren't up to the task.

For starters the rubber bushed rear control arms offer way too much rear axle movement side to side and diagonally. Not to mention, the lower control arms are a weak design and should be replaced with any sway bar upgrade.

One fix is to employ aftermarket rear control arms, which are much stronger and include a higer durometer (harder) rubber, polyurethane, or del-a-lum bushing at both ends. This increased stiffness helps to guide the rear axle up and down in it's propper path with less side to side movement. Combined with a larger rear bar, the Impala will feel much more nimble and is the route that most of us have taken thanks to the aftermarket availability.

Unfortunately, the four link design still allows some side to side movement even with the upgraded control arms. Ideally, the Impala should have a fifth link or a panhard bar similar to our F-body Camaro/Firebird friends. This fifth link runs parallel from the passenger side frame rail over to the driver's side edge of the rear axle positively locationg the axle side to side. This creates a very solid feeling ride and almost makes you forget that there is a live axle under the rear.

I have been investigating panhard options for our car for about a year now and haven't yet figured out how to fit one within the limited available space (thanks to the exaust). If the exaust pipes are dumped in front of the rear wheels like Bill Harper's setup then one would have plenty of room.

John-
Stamford, CT.

 

[Guest]

Thanks for the info, John. It is much appreciated! Your explanation makes a lot of sense. My thinking has always been that aftermarket rear control arms needed to be upgraded strickly for the safe use of a bigger bar, but now I see that there is more to it than that. The stricter positioning of the axle is a benefit all its own. Good deal! 10 more months until the car is paid off, and then I can start getting into the fun stuff!

--Paul
Avon, CT

 

[Guest]

The rear end in my '92 was pretty sloppy. I just finished replacing the weak rear springs (195,000 miles) with decent (120,000 mile)springs from my other '92 whose transmission is no longer with us. This cheap (free) replacement made a world of difference--the car's much more maneuverable, I don't fishtail the rear anymore, even though the front springs, and all 4 shocks are pretty shot. See what you can do as an interim fix for the springs--if you have a late model junk yard, the attendants usually let the customer into the yard to select the parts (supervised, of course). Bounce some of the old cop cars there, and maybe you'll get some decent springs...should be $10-20 each (don't pay more, for a little more, you could get new ones from gmpartsdirect.com).
Joe.

 

[Guest]

i know exactly what your talkin about, its very weird feeling your rear end shift but the front stays planted..

 

[Guest]

Woops! I just noticed that there was a little more discussion on this thread. Thanks for the additional input, guys. Joe, I can see how 195,000 mile springs could be significantly weaker than new! I'm at 79,500 miles right now, so I don't think my springs are in trouble yet. However, I will definitely keep your advice in mind as I slowly get into suspension mods.

So far, it sounds like my wish-list mods listed above will help with this annoying little problem. Cool!

 

[Guest]

I too experience the exact same problem. John, I too would like to thank you for your killer response!

I am going to start my mods on my new SS (new to me that is) with Eibach Springs and the bilstein 1104/929 combo. When money permits I will move on to the other mods listed by John to help eliminate this.

Paul, thanks for posting this, I have been wanting to ask this vary question and I dont think i could have so clearly stated the situation. I too travel a piece of highway here daily in which the exact same thing happens and it has been driving me nuts.

Thanks,

Low

 

[Guest]

<BLOCKQUOTE>quote:</font><HR>Originally posted by LowGun:
Paul, thanks for posting this, I have been wanting to ask this vary question and I dont think i could have so clearly stated the situation. I too travel a piece of highway here daily in which the exact same thing happens and it has been driving me nuts.

Thanks,

Low<HR></BLOCKQUOTE>


Glad I could help someone other than just myself with this question! It's funny that you mention stating the situation clearly, because it took me about three attempts! For the first two versions, I wrote it, read it back to myself and thought, "No one is going to understand what the hell I'm talking about!". So I deleted it and tried again.