🔧 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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DEEZUZ

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After further testing, I think it's likely that the diff is worn, but not broken, which makes sense for an Auburn unit that has those cone clutches that wear. It seems big shock can overwhelm the LSD, but laying into it, versus a brake torque, seems to lay down twin stripes pretty well.



Assuming this a gopro? Are you using the Skelton back door or water proof one?
 

Thirdgen89GTA

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After further testing, I think it's likely that the diff is worn, but not broken, which makes sense for an Auburn unit that has those cone clutches that wear. It seems big shock can overwhelm the LSD, but laying into it, versus a brake torque, seems to lay down twin stripes pretty well.


Hmmmmm


Corona virus, shelter in place = Get Job as Auto Journalist!

Joe: Why sir, I am considered essential to Gear Head Moral, I have to write articles about new cars.

Offer: Why are you out on the roads today?

Joe: I'm writing and article about Awesome Cars.
 

Bru

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Hmmmmm


Corona virus, shelter in place = Get Job as Auto Journalist!

Joe: Why sir, I am considered essential to Gear Head Moral, I have to write articles about new cars.

Offer: Why are you out on the roads today?

Joe: I'm writing and article about Awesome Cars.

No work involved. Took a mental health day to blow off some steam.
 

Bru

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Dusted off the orbital polisher and went to town yesterday and today. Car hasn’t been polished since 2015.

This is what I started with:

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I used a finish polish first and it definitely needed more. So went to the Adam’s two-stage polish I had and worked with the paint correction polish and Lake County orange pad. Here’s where I ended:

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Tomorrow, I think I’ll wrap with the light polish and pads (is that necessary?) and then wax.

I also want to polish the wheels though that might have to wait for another weekend. Hopefully not another 5 years.
 

Bru

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Man these cars look so good still. I want one every time I see one. Great job!

It’s an attainable aspiration. I bought mine for $4k ten years ago with 100k miles, dumped many monies into it, and now with 128k miles it’s worth $7k! :rofl:
 

Bru

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I still need to download the pics from the big camera, but I did a before and after of me sitting in the driver's seat to see how much it drops with me in it. The forums seem to think the F-body lean (driver's side higher than pass side) is to compensate for a driver's weight, so I set up the camera on a tripod and took some pics with me in it and unladen. The uneven ride height has always pissed me off.
 

Bru

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Difference in ride height with me in it was negligible. Perhaps with stock springs it would be more noticeable, but with the Stranos I didn't see the front move much at all, it was mostly the rear that did. And looking at pics, I can't really notice that much of a difference. One of those things that I notice but no one else likely does.

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