dunerida82

As I was commuting home from San Diego to Los Angeles yesterday, I decided to open up the 91 305 RS to see how much "*****" the thing really did have.

No one was in sight for a couple miles, so I decided to floor it. Slowly but surely, the 5th gear RPMs finally got up there, and I hit 105mph. Not only am I not used to driving at that high of speeds, but I felt pretty damned unstable as the thing seemed to be very shaky. The inside of the cabin rattled and overall felt like a highway to hell.

Is there anything can be done to make these things seem a little more solid at higher speeds? I mean, I like to step on it sometimes when I'm cruisin on the freeway, and sometimes I fear changing lanes. The car is pretty light, I feel like the wind might just pick me up and throw me aside. Are there any mods that can make the car feel more stable, or are all 3rd gens this way?

I understand some people use that strut tower brace. I do not know what the significance of that is, but could that be something to help?

For those with the shaky thirdgens, post away.

DartByU

Mine did that too, had the tires rebalanced and it didn't help, then I swapped to a aluminum drive shaft out of a 4th gen. and that fixed the problem, it would run to 125+ and felt rock stable.

Jokerman

My Rs feels quite stable at 100+mph. It shakes at certain speeds and then seems to smooth out so i assume its a combo of the driveshaft and the tires being a bit out of balance. If its really as violent as you say you may have some seriouse problems. Like i said the stock driveshaft causes a bit of vibration but after 85mph or so it smooths out. I have an auto so that may be part of it. Still if its really violent start checking driveline pieces.

305LG4Cutlass

I'm pretty sure I've had my Cutlass up to almost 120 (hard to tell with the 85mph speedo) and it still felt pretty stable. Not much vibration. I made sure I was on a smooth straight road when I did this but I was impressed that it handled it that well.

Air_Adam

i had my Z28 up to 110mph once... it was a little shakey, but didn't seem like anything to worry about. The only noise was coming from my hood, but thats just because it is the flimsy fibreglass type.

EvilCartman

iTrader: (1)

Had mine up to about 125 once before changing rear gears, nice and smooth up there

PantertA

I have a 91 Z and I took it up to 130 on the speedo on a nice smooth road and it felt really solid and smooth with the stock drive shaft and suspention.

Damon

I second the idea of checking tire balance and driveshaft balance. My 94 Formula had a BADLY out of balance driveshaft ahd would rattle your fillings out over 90 MPH. A Lingenfelter 3.5" aluminum shaft solved that problem.

I would also say to have the entire suspension checked out- a worn out ball joint or pounded-out suspension bushing or something like that can make a car VERY unstable at high speeds. I had my 1991 V6 RS up to over 115 on a totaly stock suspension and it was very stable. But I knew the suspenion was in perfect condition and the alignment was good. Did I mention the alignment? Thought so.

Last, if you still have the original shocks on there, give 'em a rest, OK? They're tired from over a decade of hard work. Good PERFORMANCE shocks can make a HUGE difference in high speed handling (low speed, too). There are many excelent choices on the market. Pick one, buy them and put them on.

dunerida82

Someone told me that new shocks will be beneficial, but I am just wondering if they will make the ride smoother. These thirdgens are just too flemsy feeling. I love it, but man, you drive somethin else, and the thirdgen just feels real unsolid.

DartByU

Get some good sub-frame connectors and weld them in, makes a world of difference in how solid the car feels.

Riley's35089rs+

could be a whole lot of things from tires to suspension to mounts....if you want to drive that fast...at the very least...get some z rated tires...Ive had my 3rd gen pegged over 115 and yes things are a little scary...Ive had my 4rth gen to 140...it had a slight vibration wich I'm sure was the driveshaft of u-joints...things happen pretty fast at those speeds...be careful

Justbrilliant5

My 540 sport is solid as a rock at 140. Seems like your going 80.
That why it costs soooo much !! My 305 IROC is just a cruiser in comparison.

chymos

wheels, driveshaft, check the balances...

springs, shocks, get new if they're old

subframe connectors, weld some in

strut tower brace, steering brace, install these

tires, get speed rated ones...

Energy Suspension bushing kit, get it

steering, alignment, get it checked, if parts/work are needed, get 'em

83ZMan

Both of my '92 rs' were bone stock and feel pretty good at any speed. Really nice and tight. Never had the RS V-8 past about 80 (haven't had it that long) But one day when I had the v-6 rs I had just replaced the tires and had it aligned and was on a country road. Figured I'd stretch it out a little. Got it up to 105 and it felt really good. I know I got it to 105, because that's what the Highway Partrol's radar said .............

Sonar_un

I will second you suggestion. I have had bad vibration in my car for 3 years now. I just replaced my shocks and struts, and the vibration is nearly gone. The real cause of teh vibration however was the worn out upper strut mounts. Anyway, if you seem to have a vibration that you have no idea where its coming from, do yourself a favor and look at the upper strut mounts at least. Shocks and Struts are too cheap to not justify getting some new ones either.

MikeH

iTrader: (10)

There is something realy wrong with your Drivetrain/suspension. Ive had my IROC close to 150 and it was rock solid. It would have went faster but I ran out of road. These cars are really stable at high speed. My suspension is in good shape though. And I have a hard top. I can hang with all but the best of them on the highway.

dunerida82

That is insane man. 150mph that is nuts. NASCAR runs at 180, so you aint that far behind. :rockon:

But thanks for all the tips. I think it might be time for some new shocks n struts as mentioned. After 12 years of stock shocks, it's just that time.

305sbc

iTrader: (3)

Exactly.... good point. The cheapo rubber upper strut mounts don't last forever.

Morley

Naaa, 150 is fine. I've had mine to 140+ (pegged 140 speedo) and it was rock solid. If your car is that unstable you need the entire suspension checked, as in a 4 wheel alignment and have them do a safety inspection of the suspension components.

A 3rd gen light? Not hardly. Weighing in at 3600-3800 lbs makes them one of the heavier cars on the road today.

89' RS/blue

Yeah i've had my 89' RS Camaro w/ a 2.8 up to 115, it was a little shakey. Thats when it was completely stock too. Awhile ago i put some KYB GR2 struts and shocks on there. Then i added Eibach prokit springs and a Energy Suspension Bushing kit. That made a BIG difference. The car was much more stable. But come on, you are going 110+, you've got to expect it to be a little shakey. You have to take into account that our cars 11+ years old, they aren't perfect. I think maybe lowering the car would help a bit, make you more aerodynamic. Also adding sub frame connectors would help as well. Plus you have to consider that the freeway isn't the best place to go fast. Most of them are old and abused. They are generally not smooth at all. Find a long, smooth backcountry road and you're set. When i'm on my bike on the freeway going 120 its kinda unstable, but on any other road its fine, the freeway sucks.

86TpiTransAm

I had my TA at 120mph back when it had 120,000 all all original suspension parts and it was a smooth ride.

What you have to realize is that at those speeds, even the slightest imperfection in the road seems huge with worn out suspension parts and will make the car seem shakey at high speeds.

Replace the shocks and struts as mentioned earlier. Make sure all your tires are balanced as well. An alignment would be beneficial as well. Don't worry about getting a place that does 4 wheel alignments as our thirdgens rear wheels aren't adjustable. I think most high dollar places do 4 wheel alignments but I would just take it to a mom and pop shop that does a good computer alignment.

Morley

the 4 wheel alignment is to ensure that the front and rear wheels are still in line with each other, so while the rears aren't adjustable they can be misaligned in relation to the fronts.

dunerida82

Compared to my buddies 87 Mercedes 560SEC, my Maro is a feather.

Perhaps it just seems lighter because of how it feels at high speeds.

SLP IROC-Z

iTrader: (1)

my roc with me in it weighs 3350

try usin 4th gear for top end, 5th gear is wayyy to tall to pull for top speed

MikeH

iTrader: (10)

Morley...I think your getting a Thrust angle alignment confused with a 4 wheel alignment.

Morley

the alignment i am talking about is a basic front end and checking the position of the front wheels in relation to the rears...most places call it a 4 wheel alignment, even though they can't adjust the rears.

MikeH

iTrader: (10)

Not to trying to be agruementative, But Thats called a thrust angle alignment....where you align the front wheels using the back as a reference. Hense the name thrust angle.

A 4 wheel is for cars that have 4 wheel adjustabilty. Most independent rear cars will have this.

Morley

Yes, I know. But if you go to a shop and ask for a "thrust angle alignment" they are going to give you the "deer in the headlights" look. So you ask for a 4 wheel and they do what is required for a solid axle suspension.

dunerida82

Anybody know if those strut tower braces could help the ride?

Acidtalons

From my understanding a strut tower brace would help stabilize the car at high speed by more evenly distributing load on the front suspension. However the strut tower brace is more for cornering, sorta acts like a sway bar.

dunerida82

Nice Acid, thanks. :rockon:

Spdfrk1990

My car use to shake bad at top end i was sure it was the drive shaft aslo. Last lime i got to 125 it didnt seem to bad. I need a freakin 6-speed tho i was racing imports on the freeway and was smokin them till i couldnt go over 125,130 it was around there. I dunno if it was the hydralic lifters calapsing or a speed limiter but around 125 it felt like i took my foot off the gas?? It prob was the lifters tho i was around 5 grand lo3's dont redline that high.

EYEROCK89

I have the same exact problem and it;s narrowed down to the driveshaft. From about 80mph -150mph, my car feels like it;s about to shake apart. My mechanic said that the balancing weight had rusted and had fallen off the driveshaft. There are places, machine shops, that can balance your driveshaft for you.

Spdfrk1990

yeh i know i was thinking about gettin a aluminum 1.

Crisis

Mine's stable... do what i did

da bad guy

i have a 87 z28 just bought it two weeks ago on the way home i hit doughty road to get a feel for it and smoke the tires all the way to 40 finally let off the gas at a buck 45 i was impressed compared to the rental cars i beat on everyday at work... my *** the difference between a v6 and v8 is so obvious .... ha and just think i wanted a honda crx boooooring

Cronic3rd

I had my formula up past 115 or so (I don't know what i was going the speedo stopps at 85, all I know is that I left 2 mustangs and a probe in my dust - the vette was the only one whould caught me) and it was pretty solid, I was more afraid of my tires giving way than the suspention.

vette9190

iTrader: (2)

I had my 87 LT Camaro up to 150 when she started to lift( no G-effects on that model and super light compared to RS or Z28s).
I had my 92 Bird up to 110 every day to and from work for 40 miles for 8mos rock solid.
I havehad my current car a 91 RS up to 110 and aside from a rear wheel noise cxaused by an inbalance of the tire it was rock solid.
I love the handle on these F-bodies.

87WS6

iTrader: (1)

I have had my 87 Trans-AM to 120. No problems at all.

Dr G

I've had my GTA up to 130mph and it still felt rock solid.

Chymos and everyone else have covered most of the things to check and do.

Let us know once you get the car checked over and sorted out.

RMK

155mph and it didn't wobble the slightest bit. The only problem I had was a little T-Top noise, but that's sorted now. 160 comming this summer form the little 305.

azvolfan

RMK,

How did you take care of your t-top niose. I have the same problem at highway speeds.

chevyboy07 91

my Z runs 160+ and has ZERO problems up there. Feels like Im running at about 80 or so. Its great spraying the crotch rockets and running side by side w/ some of them...even pulling every now and again

RMK

The holes where the sliding rods go into when you lock the top in place have adjusting screws. Loosen the screws and rotate the small circular thing that the rod goes into so that the top is pulled down firmly when you use the lever to lock them in place.

Sorry I don't have pics. It should only take you 10 minutes to get it right. The most annoying part is taking the tops on and off while adjusting it.

azvolfan

Thanks. I will give it a try.

dunerida82

The advice was perfect. Thanks all.