🔧 BUILD Quest for improved 4th gen Fbody drivability

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I wanted to update this thread (June 2023) with a more detailed summary of the 14-year journey with my 1998 Trans Am. In my day job, I'm an automotive journalist, so I drive a lot of performance cars, and every winter when the TA is under the cover I’m tempted to buy something new after driving the latest and greatest all year, but then every spring I get back behind the wheel and regain enthusiasm to keep at it. My goal over the last couple of years was to give it as much updating as possible to build a well-rounded late-model muscle car that blurs the line between muscle car and sports car, just how the new Camaro and Mustang have evolved over the years. And to get there, I had to correct a lot of self-inflicted mistakes that ruined the car’s drivability without much gain. This is quite the write-up for an only mildly interesting car, but verboseness comes with the territory, so here we go:

I bought the car from my cousin’s husband in 2009 for $4,000 with 100,000 miles. Their priorities shifted and the car was in need a lot of maintenance; it ran poorly, had dry-rotted tires and was in barn storage so it came with a family of mice for no extra charge.

What I bought was a stock 98 Trans Am with 16-inch wheels, sleek beak hood and SLP loudmouth exhaust. I immediately added drag radials, addressed the maintenance items and went to the drag strip, hoping for high 12s, low 13s because that was my expectation after being on LS1Tech for 5 minutes. HA. Well, the fastest F-Bodies run those times in later build years with 3.23/3.42 gears, LS6 intakes and factory production tweaks to the cam/heads. In stock configuration with loudmouth exhaust, my 98 with 2.73 gears, LS1 intake and 853 heads ran anywhere between 13.6 and 14.0 seconds, which was slower than my (at-the-time) daily driver mildly modded Grand Prix GTP.

From there, I added a Yank SS3600 torque converter and rear tubular lower control arms, which knocked 8/10ths of a second off the quarter-mile time to run consistent 12.8s; sub-frame connectors also went on at this time and really helped clean up the rattles and looseness of how the car flexed over bumps.

And then I ruined the car for a few years with poor choices.

I put a lot of trust into a performance shop that picked an inappropriate cam and didn’t put the effort into tuning. The car wouldn’t start when hot, it inconsistently idled and the torque converter tuning would make the car lug and vibrate. It was really a couple of miserable years with a loud, annoying and slow car. The cam was 231/235 .617/.621 113+3 with stock heads and a really mismatched powerband for an auto car with 2.73 gears. The car also had an LS6 intake, 42-pound injectors, 1 3/4 headers, off-road Y-pipe and Magnaflow exhaust. From there, I found a new tuner who fixed all the drivability issues so it drove much nicer, and then added 3.73 gears.

I had it dyno’d a few times in this configuration. The initial shop’s dyno spit out 401 rwhp. On a Dynojet at Dean's Performance with the revised tune, numbers were 370/345 in third gear with the converter unlocked. And then I had it dyno tuned from Speed Inc where it made 380 rwhp and 355 rwtq on their Dynojet. But it I was still disappointed at the track, running a best 12.0 at 113 mph. Looking back, that initial shop’s first dyno was laughable considering the trap speed and how poorly the car drove.

During this time, I also played a lot with the exhaust, finally settling on a Kooks catted Y with true merge, versus the ugly T-merges from previous designs that created that awful hammering sound at part-throttle.

And then I decided to take a big swing at the car. Up to this point, I had been running QA1 shocks at the back with drag radials, while up front was stock shocks/springs and summer tires. I hated how the car drove with a clear imbalance between the front end’s tightness and rear end’s looseness. I also had a drag-oriented short torque arm. So off all that went and in come the final suspension setup: Koni shocks, Strano springs, Strano sway bars, UMI long torque arm, double-adjustable lower control arms, adjustable panhard bar and a few other things. Holy smokes. Besides the converter, it was probably one of the biggest changes to how the car drives. Tight, controlled, responsive. It was like driving a car 20 years newer, instead of a bucket of bolts like how it drove with the old suspension.

Under the hood, I had Pat G from LS1Tech spec out a combo that would give stock-like drivability but with 11-second potential. It consisted of a pair of 799 heads (Z06-equivalent) pulled from a junkyard, which I had cleaned up and checked out, and an EPS cam with the following specs: 222/226 .626”/.626” 115 LSA +3, as well as a refresh of the valve train with trunion upgrade on stock rockers instead of something fancy the other shop installed. With this milder cam and upgraded heads with more compression, the car saw a giant torque increase under the curve, and power was much more usable and better matched to the auto trans. Now, I was making 390/375 to the wheels on Speed Inc’s dyno, but with a lot more power and torque under the curve and stock-like drivability.

That resulted in 11.82 @ 115 mph, and it has trapped as high as 117 mph. I consider this very impressive because it drives like it did when stock and power is accessible all over the place. Since then, I’ve installed a chrs1313 A/C ram air and have a dedicated set of C5 17-inch wheels with Hoosier drag radials to try and hit 11.50s, but my last time to the track with the setup was a bust because (as I discovered afterward) the throttle blade wasn’t going WOT thanks to the throttle cable adjustment being unclipped.

I still enjoy driving the car. I debate what to do with it (sell or keep) because I also feel a sense of stewardship to keep this car on the road looking and driving as good as I can make it. All the kids in the neighborhood turn around and give it a thumbs up when I drive past, and my kids (2 and 5 years old) call it “Dad’s Trans Am.” They pretend work on their cozy coupe (like dad’s car). I know it’s superficial, but I don’t think I’d get that kind of engagement in a CTS-V or newer car. Or maybe I would, because they could actually ride in a car that properly fit child safety seats … the debate continues.

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Bru

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I just spent 1,200 miles on the new setup during TCG Tour and wanted to share my thoughts. My goal for this car is to drive as much like a modern muscle car as possible, which is impossible given the chassis rigidity of newer cars but I wanted to see how close I could take this thing. As a reminder, here's what I added:

-Koni Yellow Sport adjustable shocks (replacing Bilstein HD)
-Strano 35 mm/ 22 bar set (replacing stock)
-UMI LCA with rod end to reduce binding (replacing poly ended)
-UMI long torque arm with relocation bracket (replacing short TQ arm)
-Hawk slotted rotors and 5.0 pads (replacing stock)
-Matching tires front and rear, Conti Extreme DW stock sized (replacing drag radials)
Already installed: Strano springs

Those concerned about a balanced handling experience need to ditch drag radials in the back. Handling was absolute garbage even with a mild drag radial like the Nitto 555Rs, and I didn't realize it until installing the matching tires on all four corners. The soft-sidewall drag radial out back and a stiff-sidewall summer tire up front created an ill-handling car where the front and rear were disconnected from each other. The front turned in sharp and crisp while the back responded slower than the front and created a very odd sensation that was totally the tires, which I installed before any other mods.

The Continental tires are good, but either the 17-inch size (274/40/17) doesn't have the steering feel I was hoping for with a too-tall sidewall, or the tires just don't communicate turn-in very well. I wish there was more steering feedback that I felt more of even with the Sumitomo summer tires. The Continentals seem to make a lot of noise near their grip limits, which I didn't mind so much still learning the car. If I did anything more to maximize this setup, it would be an 18-inch package front and rear with wider, more aggressive tires.

On to the suspension. The Konis completely transformed this car. I wasn't sure they would be a huge difference over the Bilstein HDs but let me tell you this is a completely different car. Like going from a base Camaro to 1LE, which may not seem like that big of a difference but the base Camaro SS drove horribly compared with the 1LE. With Konis, the car rides better in the general sense of ride quality. There are fewer body noises and hatch rattles, and the car is more controlled over rough roads.

After dialing up the suspension firmness, the car is considerably more responsive and quicker to turn. Even a little twitch of the steering wheel results in the nose changing directions. It's hyper-sensitive and almost too high strung for my tastes. Luckily it's also adjustable. Handling is massively improved. I didn't think a fourth-gen could drive like this. I feel the setup is now limited by the tire choice considering even when the tires are squealing the car is flat and composed.

The brakes are holy-shit levels of goodness. Again, I didn't think an F-Body could stop this well and the new pads/rotors really whoa this thing down. No squealing or noise, and the coated rotors will keep the hats looking good for a long time I hope (no rust). It stops so aggressively that the left turn signal illuminated during a few intentional panic stops - not really sure what that's about.

I really want to get this on an autox course. An open circuit would be fun but the automatic transmission blows for corner exit and would likely grenade trying to hold a gear, plus I'd need an oil and power steering cooler, so autox is easier on the car and probably what I'll do next. It's still a riot of a street car even if neither of those happen.

The items I added to improve drivability worked well, like the long torque arm to reduce road noise, but noisy summer tires and poly-or-rod-ended parts underneath plus leaking t-top seals made the car exhausting to drive 1,200 miles with very poor levels of wind and road noise. I accept that, because it's an 18-year old F-Body with 120,000 miles.
 

Thirdgen89GTA

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Damn, serious suspension there.

Any reason you didn't go with the UMI Roto-joint stuff instead of the Spherical REs?

Also, for tires, I'd look into the Nitto NT05's or the Falcon Azeni's RT615ks. Those are the better choices for a summer performance tire in the 275/40/17 size. I have the NT05's, and though they are getting older, when warm they grip damn good. When cold though entirely different story. The 615k's are better than the NT05s.
 

The Beast

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Damn, serious suspension there.

Any reason you didn't go with the UMI Roto-joint stuff instead of the Spherical REs?e the

Also, for tires, I'd look into the Nitto NT05's or the Falcon Azeni's RT615ks. Those are the better choices for a summer performance tire in the 275/40/17 size. I have the NT05's, and though they are getting older, when warm they grip damn good. When cold though entirely different story. The 615k's are better than the NT05s.



The falcon Azenis rt615 tires are awesome tires I have them all around my fbody and made the mistake of taking the rears off for mickey Thompson DR for a few weeks and went back to the Falcons. Thanks for the info on the 5.0 pads.
 

Bru

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Damn, serious suspension there.

Any reason you didn't go with the UMI Roto-joint stuff instead of the Spherical REs?

Also, for tires, I'd look into the Nitto NT05's or the Falcon Azeni's RT615ks. Those are the better choices for a summer performance tire in the 275/40/17 size. I have the NT05's, and though they are getting older, when warm they grip damn good. When cold though entirely different story. The 615k's are better than the NT05s.


I wanted to retain some NVH qualities.
 

Thirdgen89GTA

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I wanted to retain some NVH qualities.

The Roto-joint uses delrin bushed spherical rod-ends, so they actually transmit slightly less noise to the cabin, but without any impact on articulation. I like the fact that as the del-rin wears its adjustable and eventually replaceable for cheap.

Thats why I'm curious that you went with straight spherical rod-ends.

rotojoint.jpg
 

Gone_2022

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I need those brakes badly as well...... on to another question

Bru,

Prior to all these upgrades did you ever have squeaking rattling over bumps especially from the rear? I have upgraded and replaced my suspension with QA1's all the way around and the squeak is still there. The car has an upgraded rear sway bar with boly bushings on the links as well as upgraded rear lower control arms.

I have a feeling these bushings may be causing my noises rubbing together although I am not sure.

Thoughts if you have had this noise?
 

Bru

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I need those brakes badly as well...... on to another question

Bru,

Prior to all these upgrades did you ever have squeaking rattling over bumps especially from the rear? I have upgraded and replaced my suspension with QA1's all the way around and the squeak is still there. The car has an upgraded rear sway bar with boly bushings on the links as well as upgraded rear lower control arms.

I have a feeling these bushings may be causing my noises rubbing together although I am not sure.

Thoughts if you have had this noise?

I did, but it was the exhaust. I could also hear it at idle with the lumpy cam, but with the smoother idle of this cam I no longer hear the squeaking.
 

Pressure Ratio

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Poly bushings can squeak. They need routine maintenance using the proper grease. Poly does not like to articulate or rotate like rubber does. So it needs to be lubricated to allow them to move freely.

But like Bru said, there could be other things causing it as well. Sometimes those annoying noises, rattles, and thuds can be a pain to diagnose and fix.
 

Intel

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I will look into that, I assume thats what it is. Both the control arms as well as the sway bar and pan hard bar all have the red poly bushings. It is more of an annoyance and embarrassing thing when someone is riding in the car.

Wrap the swaybar in teflon tape where it mounts to the car if you haven't already. I do it now to every sway bar along with grease and it cuts down on the noise.
 

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