Here's a "S4 GT" I found on a broker lot one day. < There is no such designation from Porsche >

In 1989, Porsche ups the ante again, this time delivering a 'serious sporting machine for the solvent'. The GT is a special version featuring a revised 5.0 liter 330HP V8, sport suspension and all new seven-spoke Club Sport rims (note 1), the rears the widest yet from Porsche measuring 16 x 9" wide. As such, the GT comes only with a manual trans. Visually imperceptible but an improvement functionally, the shiftrod is shortened 1" from the manual S4. Driver and passenger-side airbags introduced and Porsche becomes the first to make them standard across the model line. New low-pressure tire warning system is standard.   

From 959 technology, the 928 GT is fitted with an electronically controlled liminted slip differential. The LSD has a progressively lockable multiplate clutch installed with the rear differential (note 2). A computer monitors wheelspin and clutches the affected wheel. Also new is a tire pressure warning system utilizing a pair of sensors integrated into each wheel. The wheels themselves made a change from the original Club Sport wheel in model year 1989 to the forged Design 90 style beginning in 1990.  Price: $76,500 (note 3) 

Exact 928 GT production figures are unknown to the author but have been guesstimated as follows:
1989/90 - 50 US cars; 1990 - 100 US cars; 1991- ? 1992 - no official 928's produced, see the 1993 928 GTS. 

(In response to market, Porsche introduces the hotter engined GT mid model year in 1989.  Thus there are both manual and automatic 1989 928 S4's.  For model years 1990-1991, the 928 S4 continues on as before but comes only with 316hp and the 4-speed automatic) 

(note 1.) Club Sport see 928 S4 info  (note 2.) Motor, August 1988  (note 3.) Car and Driver, July 1990 

 Year  Type  HP@rpm  Engine Serial Number  Chassis Serial Number
 1990  928 GT  326@6000  * need factory clarification  WPOJBO920LS860001-0518
 1991  928 GT  326@6000  * need factory clarification  WPOAA292xMS810001-0448
table source: The Porsche Family Tree, published by the Porsche Club of America

* the engine s/n from the PCA tables have been omitted so that we may verify them with Porsche.  If your need is immediate please purchase the tech spec booklet.  other note:  peak hp has been recorded at slightly higher rpm value of 6200 rpm.  This page will be corrected...note: chassis numbers given above shared with 928 S4 cars

note: 928 GTs were available beginning with model year 1989. (Updated numbers will be posted) 

To: 928 porschefans <> 
Subject: 928 GT identification 


Barring any original car documentation which denotes serial numbers, the 
only way to authenticate a GT will have to come from the Certificate of 
Authencity ie. the cardex info. (This will rule out any creative engine/trans/dash swaps). 

Code 639 or 637, denoting GT, may not always appear on the build sticker in the trunk for 
some reason (it doesn't on my GT and a few others have responded same 
here on porschefans).  The presence or lack of code 474, sport 
suspension, is no indicator as well (my black Boge equipped car lacks 
this also !?!). 

So, what the cardex will tell you (from my experience with the 1990 
model) is: 
Engine serial number   (ex. 85L00855 - all GT engines begin with 85) 
Trans serial number  (ex. 3L00788) 
Paint code (ex. Baltic blue metallic C7C7) 
Interior code   (ex. Silk Grey Leather, Blue Leather, Leatherette QQ) 
Optional equipment 
and curiously enough... the 928 GT is identified by Porsche only as "928 S4" 

This same anomaly may apply to Club Sport / SE editions as well. 

If anyone has info on shortcuts to getting the cardex info please let us 
all know as one won't always have the luxury of time for snail mail when 
shark hunting! 

For those in the field shopping right now, verifying engine code M28.47 
and trans code G28/55 (note these are 'type' not serial numbers) is a fairly 
safe bet that you are indeed looking at a real GT, but again, only the factory 
cardex will provide the serial numbers. 

Phil Tong 
PCA - Golden Gate Region 


Phil and Paul, 

Phil, I know you prompted me for a response on this topic earlier in the month 
and I didn't respond due to my travel schedule.  Here's my .02 on this topic. 
Besides the identification numbers on the engine and option codes there are 
some esthetic differences.  The most obvious on an 89 GT are the wheels.  They 
are the forged "Club Sport" alloys that were the same basic style as those on 
the 944 Turbo S's and appeared only on the 89 GT(club sport - ROW) models 
only.  The only other exterior visual is the twin exhaust outlets, 1989 S4 5 
speeds (like mine)have a single outlet and the GT's have dual outlets.  On the 
inside the only difference would be the length of the shifter.  In a GT it is 
the shorter shift lever while S4's have the longer shift lever found in early 
928's.  Of course we all know that Porsche has been known to throw curves from 
time to time and use whatever parts happen to be handy so this is a rule of 

I have attached a scan of an 89 GT that I recently considered trading my S4 
for.  Notice the wheels and the option sticker codes.  The sticker has the 
GT(639) option and the sport supension(474) option. 


Chuck Zachman 
Vice President - Carolinas Region PCA 
1989 928 S4 ( 5 speed )

  note engine code M2847-85K  and trans code G2855!!!
The codes follow GT identification and most definitely the 85K an 1989 928 GT engine...  Now all that's left is to eyeball the numbers on the physical components and pay the man!