Porsche 928 S4 Differential Gasket and Fluid Replacement / Change

Changing Porsche 928 S4 Differential Gasket and Fluid

I recently took on the task of replacing my 1989 Porsche 928 S4 differential gasket and fluid. When you look at videos online the Porsche 928 S4 has a different size Allen Key than the non S4.  Here are the general steps I used, this is to aid with the manual:

  1. Buy AMSOIL Severe Gear 75W 90 4 Quarts (you will have some left over)
  2. Buy the pump (its only a couple dollars)
  3. Buy new crush rings, its the cheapest Porsche part I have ever bought. Less than $1.25 at the dealer.
  4. Evenly raise car in the air and put on stands. Never get under the car without stands.
  5. Clean the differential for several hours. You don’t want any grime inside your differential.
  6. Place oil pan under car.
  7. Open the fill plug and take off. If you cannot remove this do no proceed without an experts help.
  8. Open the drain plug and lets all the oil fluid drain.
  9. If you only want to change the fluid simply put the drain plug back in and torque to the manual specs. Then fill up using the pump. I don’t think its possible to not use a pump because of the location of the fill hole. Make sure you pump some gear oil on the threads of the drain and fill plugs to they don’t get corroded. Also torque to the specs in the manual.
  10. If you want to take off the cover to replace the gasket you need to drain the fluid.
  11. Loosen the exhaust clamps so you can move the exhaust piped out of the way.
  12. Remove heat shield off of the differential using the special tool, I took a picture of it.
  13. Remove the differential cover
  14. Replace gasket, put back on drain plug, fill up, and put back on fill plug.
open box containing amsoil pump
This is what the AMSOIL pump looks like
porsche 928 s4 differential gears
Inside view of Porsche 928 S4 differential gears
inside view of porsche 928 differntial cover and old gasket
Porsche 928 s4 inside view of differential cover
porsche 928 s4 differential cover
close up of Porsche 928 S4differential cover

placing porsche differential gasket on gover
Porsche differential gasket
AMSOIl Oil Pump
Very useful AMSOIL pump, it fits on Quarts and Gallons


i cleaned the end of the porsche 928 s4 differential drain plug
Porsche 928 magnet in the differential drain plug.
old gear fluid draining into drip pan
Image of old gear fluid draining
Image of Porsche 928 differential drain plug


oil on differential drain plug threads
i put oil on the drain plug so it does not corrode

loosing the differential drain plug on porsche 928 s4
I am removing the Porsche 928 s4 differential drain plug


wrong tool
i tried using a socket that was too big. it turns out the s4 drain plug is different than the non-s4


special tool in use for removing 928 heat shield
i had to buy this special tool to remove the Porsche 928 s4 differential heat shield

porsche 928 differential tool
here is the special tools i had to buy for the differential heat shield, they are not normal Allen keys
here is the porsche 928 differential crush rings
Porsche 928 differential crush rings


image of porsche 928 drain plug hole
image of drain plug hole