🔧 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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The alternator crapped out on me and must have been on the decline for a while because the car picked up serious MPG after replacing. I'd typically get 100 miles or so out of a half tank during highway cruising, and on a recent trip I just got 165 miles on a half tank, which I backed up on the flip side of the trip. I can't tell if it's in my head, but part-throttle cruising feels smoother and I swear coolant temps are running cooler than normally in these temps; maybe the fans weren't drawing enough power? Pretty crazy replacing the alternator made that big of a difference. I thought it could also have been because I had the battery disconnected but the battery has been disconnected recently and didn't make this kind of difference. I wonder if the new alternator could have impacted power at all. Roads have been wet so didn't get a chance to crack it open. Car is running spectacular now for 120,000 miles.
 

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After sitting four months with the battery connected and no tender, the car fired right up. :rofl: Didn't expect that. Climate controlled garage probably helped.

Plans this year are to have the catted Y and Magnaflow cat-back matched. Surprisingly, the Y outlet is only 2 3/4 and not 3 - so stupid - so there's a leak. And then I'd like to have the Magnaflow cannons replaced with the corsa clones i bought last year.

I dread finding an exhaust shop in my area. It's so hard to find someone who does respectable exhaust work.
 

Bru

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One of these popped up on eBay so I bought it. They're not hard to find but some people want stupid prices because they were discontinued a while back and this wasn't bad. I figure once it's built the model will be a nice reminder if I ever sell the car.

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Bru

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Exhaust work is done. The Kooks Y hugs the floorboard better now and doesn't hit, and I can clear my garage entrance. The tips and fixing the Kooks to Magnaflow leak has cleaned up the sound. Those Magnaflow cannons projected the sound like, well, a damn cannon. The quad tip corsa clones have a punchier sound with less blasting and have completely changed the tone of the exhaust. They need to be raised a little. It's also nice they make the rear look wider.

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Also, I wanted some new floormats so ordered these, which seem decent enough and were more affordable than the others but feel of high quality.

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Bru

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Literally have done nothing to the car other than put gas in it. And now chasing an oil leak. It’s always sweated a little horsepower from the pan, but after driving for a half hour I’m getting a burnt oil smell from under the hood. Hoping something simple like valve covers. They’ve been on and off a bunch of times. Also thinking about a cut-out. Cats, magnaflow and baby cam don’t make much noise.
 

Bru

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My Dad sent me a listing for one the other day and I thought of your car..... It does't seem that long ago that you were making all the drive ability upgrades. Time really does fly


I’ve had the car 10 years now. Love the current setup. A manual transmission would be cool, but if I had the knowledge and drive I think it would be sweet to investigate that DCT swap for Supras (BMW Trans) and see if it would work in an F-Body. 10-or-8-speed auto would also be nice.
 

Gone_2022

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I’ve had the car 10 years now. Love the current setup. A manual transmission would be cool, but if I had the knowledge and drive I think it would be sweet to investigate that DCT swap for Supras (BMW Trans) and see if it would work in an F-Body. 10-or-8-speed auto would also be nice.



Honestly wondered why this was never a thing. Swapping the new better speed transmission into older f bodies.

Basically you have 3 trans choices right now.....

4l60 built if you want to totally waste your money

4l80 swap if you want to keep OD and lockup

Turbo 400- if you want the cheapest way to handle 1500 hp
 

Bru

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Two interactions this weekend reminded me why I keep hanging onto this car.

While driving through downtown Naperville, some kid, like 12 years old, waves for my attention until I turn and look, then chucks the deuce at me and nods up. :rofl: Made me laugh, and my wife got a kick out of it too. That kid doesn’t know what this car is, other than something that looks like knock-off Batmobile.

I also picked up the groceries (Mariano’s clicklist, life-saver) and the kid who brought the cart out asked if I was sure that everything would fit. I opened the hatch and he went, “Whoa, I didn’t know these do that. There’s so much more room than a Mustang”. Got a kick out of that. Then I proceeded to blast onto 75th street and this happened to the groceries.

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On the downside, the oil pan leak (maybe rear seal leak too) has gotten bad enough that oil is seeping back on the trans pan and y-pipe, so once it gets hot I smell oil. And there’s a moaning reciprocating sound in reverse that correlating with speed. Car’s been maintenance-free for too many years, anyway.
 

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