smyth1

trying to determine the difference between the two.did they just change the badging?

Marine Blue

Definitely do a search on here, there is tons of info. IMHO the cars "feel" very different inside, the GT feels much more modern. Engine also feels different, where the S4 has more torque down low and the GT really picks up after 4000 RPM. On the outside they look the same with exception to the wheels and exhaust.

AO

Roof mounted antenna is also an exterior difference.

The GT's also changes a bit from year to year.

Wikipedia has a good breakdown of the changes from year-to-year.

http://en.wikipedia.org/wiki/Porsche_928

auzivision

GT has hotter cams, higher compression, different piston, different tune, shorter gears, different exhaust, and is somewhat lighter. No significant differenced between S4 and GT interiors when comparing same years. Interior for both models received digi-dashes in 89 and airbags in 90. 87 & 88 were all S4's, 89, 90, 91 were either S4 or GT... then only GTS after that.

Following are some interesting details copied from Wiki:

The 928 S4 variant debuted in the second half of 1986 as a 1987 model, an updated version of the 5.0 L V8 for all markets producing 320 PS (235 kW/316 hp), sporting a new single-disc clutch in manual gearbox cars, larger torque converter in automatics and fairly significant styling updates which gave the car a cleaner, sleeker look. S4 was much closer to being a truly world car than previous models as only major differences between ROW and US models were instrumentation in either kilometers or miles, lighting, front and rear bumper shocks and the availability of catalytic converters in many ROW markets. The Australian market version was only one with different horsepower rating at 300 PS (221 kW/296 hp) due to preparation for possible low grade fuel. Even this was achieved without engine changes.

A Club Sport variant which was up to 100 kg (220 lb) lighter became available to continental Europe and U.S. in 1988. This model was watered down version of 1987 factory prototype which had lightened body and 10.9:1 compression ratio engine. Also in 1987 the factory made four white lightened manual gearbox S4 models for racecar drivers who were on their payroll at the time. These were close to same as later actual Club Sport models and can also be considered prototypes for it. An SE (sometimes called the S4 Sport due to model designation on rear bumper), a sort of halfway point between a normally equipped S4 and the more race-oriented Club Sport, became available to the UK. It's generally believed these Porsche Motorsport engined cars have more hp than the S4. They utilize parts which later became known as GT pistons, cams, engine ECU programs and a stronger, short geared manual gearbox. The automatic gearbox was not available.

For 1989 model year visible change inside was digital trip computer in dashboard. At the same time Australian models received the same 320 PS (235 kW/316 hp) engine management setup as other markets. Porsche debuted the 928 GT in the late winter 1988/89 after dropping the slowly selling CS and SE. In terms of equipment, the GT was like the 928 SE, having more equipment than a Club Sport model but less than a 928 S4 to keep the weight down somewhat. It had the ZF 40% limited-slip differential as standard like the Club Sport and SE before it. Also like the CS and SE, the GT was only available with a manual gearbox. ROW 1989 CS and GT wheels had an RDK tire pressure monitoring system as standard. This was also optional for the same year ROW S4. For 1990 model year Porsche made RDK and a 0-100% variable ratio limited-slip called PSD (Porsche SperrDifferential) standard in both GT and S4 models for all markets. This system is much like the one from the 959 and gives the vehicle even more grip. In 1990 the S4 was no longer available with a manual gearbox.

The S4 and GT variants were both cut at the end of 1991 model year, making way for the final version of the 928. The 928 GTS came for sale in late 1991 as a 1992 model in Europe and in spring of 1992 as an early 1993 model in North America. Changed bodywork, larger front brakes and a new, more powerful 5.4 L, 350 PS (257 kW/345 hp) engine were the big advertised changes; what Porsche wasn't advertising was the price. Loaded GTS models could eclipse $100,000 USD in 1995, making them among the most expensive cars on the road at the time. This severely hampered sales despite the model's high competency and long standard equipment list. Porsche discontinued the GTS model that year after shipping only 77 of them to the United States. Total worldwide production for all years was a little over 61,000 cars.

(Edit... too funny I was typing when AO slipped that in. I think S4 also had roof mounted atennas.)

Hilton

Yep, my '89 manual S4 is indistinguishable from an '89 GT except for these externally visible differences:

1. Single-pipe S4 rear muffler (GT had twin-pipe "Sports exhaust")
2. Stock S4 shifter is longer than the GT one, although the usual 928intl short-shifter is shorter
3. Badging (duh - but I had to put it before someone else added it)

Otherwise, physically the cars are very similar. The differences are mechanical and hidden beneath the skin:

Hotter cams on GT
Port-matched intake on GT
G28/55 gearbox on GT with 2.73 final drive (G28/12 on manual S4 with 2.64 final drive)

That's pretty much it as far a I can recall. GT got "higher compression" than 87/88 S4's, however my experience with my '89 5-spd S4 is that compression is also higher than '87 S4's (based on compression tests and throttle response).

VehiGAZ

More MY difference info here too.

The '89 GT got rolled fender lips, so that's another "exterior" difference as well, although it is not exactly "visible" - you have to feel for it.

The GT got the sport suspension and 40% mechanical LSD baked into the package.

S4ordie

S4 = Mylie Cyrus

GT = Lindsay Lohan

Both very capable of good performance - one's a bit more high strung and likely to land you in jail.

Stromius

But for $1800 dollars Mylie can go to Dr Colin cam shoppe and get 'cams' bigger than Lindsay's and look hotter too

cams (w/o in$tall) $1800
short shifter $75
lighter muffler $250

Price premium for a true GT > $2200

AO

Forgot about the port matched intake.

I like hotter cams... I knew there was a reason I like Lilo over Mycy. Dirty girls are the best!

Marine Blue

I also didn't bring up the PSD. It works incredibly well and really does an amazing job keeping the rear planted in corners. You can feel it working and the feedback allows you to keep pushing the car to its limits very comfortably. There is some added maintenance that comes with the system.

Tom. M

Nah....more like
S4 = Jennifer Aniston

GT = Angelina Jolie..

Both are super hot in their own way....but Jolie ..has that extra "unpredictable" edge

cali4sun

Just got the new PCA Panorama last night. Did anyone see the listing for a 1990 928 GT for $11,500 under 100K miles for sale in the classifieds I think it was in New Jersey. I thought that my be worth checking out........I'm not at home,otherwise I would have listed it's details.....

'89 S4 GP White/Black
'76 912e Silver/Black

pcar928fan

S4's from the same year as GT's also have roof mounted antenna. Those started in '89...all '89 and up 928's have roof mounted antenna.

If you are going to track the car, don't buy a GT...S4 5spd is ok, but there is something about the GT's and taking them to the track that ends up costing you a motor... I know, I know, 10 of you are going to pipe up and say you have never had a problem w/ your GT at the track... Great for you! Now tell the 3 GT owners that I actually KNOW who have each burned up AT LEAST ONE MOTOR on the track your story... they won't care! You would certainly think the GT would be THE TRACK car, but I don't know any S4 5spds that have lost a motor on track (I am sure there are more than a few that have though...I just don't know them) but I have never known a GT that didn't blow up on track. YMMV!

An S4 with sport suspension should feel almost identical to a GT...*should* being the operative word here. GT's generally had manual sport seats so that probably saves a few lbs, also I think the final section of muffler is lighter too...again saving a few lbs. Power is close to the same (the hotter cams in the GT get you an extra 10hp, but no extra Tq).

cali4sun

Did the GT actually have badging from the factory on its rear?

'89 S4 GP White/Black
'76 912e Silver/Black

AO

Yes, but there was an option to delete it. Mine came deleted.