Just some clarifications for the posts regarding Power Steering in the
At the time of the 928's development the recommended fluid type was Dexron II. Dexron “ II” was replaced by Dexron “III”. You can use either. You
can mix either. However, you should remove and flush out the old fluid every few years for optimum system life. If any moisture enters the system it will settle in the rack and cause the rack shaft to rust, hence the rack shaft seal will be damaged. There is no exact time frame for fluid replacement so it is best to check your fluid level when ever you check your engine oil level. Since the system is a closed loop system the fluid level in the reservoir tank should always be the same .. FULL.
If the level drops then you have leak somewhere and you need to repair it otherwise the pump will be damaged. You can examine the fluid for color
consistency and odor. Typically Dexron is a clear red color. Some brands tend to be less red than others. The fluid should smell like a fresh bottle of fluid. If it smells pungently burnt then flush the system and inspect your pump.
You can use any major brand of fluid. One is not better than the other.
You don’t need synthetics (the temps never get that high to warrant their use) and in our opinion there is no observable or measurable gain in using synthetics (there can be a controversy on the benefit of synthetics, however we have yet to see any noticeable benefits upon inspecting components nor realized cost-benefits). Be cautious of using any fluid that contains significant “ester” based oils, or fluids that claim to “restore” or “revitalize” seal life. Some of these non traditional fluids will degrade seals and hoses. And, no fluid will fix a leaky system.
OTHER SYSTEMS vs. the 928:
The 928 power system (rack, pump and hoses) are respectable, and if maintained properly will give you years of use. From 1978 through approximately 1990, the pump pressure was set at 75 bars max ( 1 bar = 14.5 nominal psi.) or 1087.5 psi. Subsequently the pressure was raised to 100 bars or 1450 psi. In comparison to the old Audi 5000 and 100 systems, their nominal pressure was 150 bars and used a different type seal design and fluid. Sorry Audi owners.
Means checking yearly for: (a) cracked, gummy or worn rack boots and replacing them as needed, (b) correctly inspecting and replacing the tie rod assemblies, the inner tie rods must be inspected when they are “not under load”, (c) fluid inspection, (d) leak inspection, (e) rack mount bushing inspection, and (e) rack shaft greasing.
Rack Year Differences: there were basically 3 different rack part numbers, the B, C and D suffixes. After remanufacturing over two thousand (2000)
928 racks we tell you only what we have observed, and that is basically all three versions are the same with respect to performance. The physical differences are as follows: 1978-81 used the dash “22" or “B” version.
1982-1990 used the dash “24" or “C” and 1991 onward used the -27 and -27 or “D” versions. All versions have the same ratio and piston area (if
you want to quicker ration get a smaller diameter steering wheel), and have no noticeable difference with regard to spool valve (torque bar) opening curves. With respect to replacing an early version with a later or visa-versa, you have nothing to gain expect the mid year B versions are approximately 3-4 pound lighter than later C & D versions (for you weight conscious racers it would be less expensive to go on a diet).
If someone told you one version responded better than another with regard to “feel”, we can point to 3 possible component items in “any” rack to inspect which could cause subtle differences.
REBUILD OR BUY:
If you have the time and money then you can do just about anything.
However, unless you have been down this road before and know all of its bumps and turns, I can think of a dozen other things I’d rather be doing than learning how to rebuild a rack “consistently”, and they are playing with my kids, driving my car, golfing, fishing, watching the NASDAQ or doing the list of chores around the house (I won’t tell you my preferences). If on the other hand you are retired and filthy rich from playing the NASDAQ short and long, well by all means get out your tools and take out that rack, been there done that. Then go on the web or ebay and get that seal kit. Then take that puppy (the rack) apart and fix it.
If by chance the spool valve body housing does not have ring grooves, the spool valve springs are not broken, the shaft surface is not rusted (you know the correct micro finish for optimum seal life), you know how to improvise seal insertion and removal tools, you know how to recondition the cylinder bore diameter, set the best back lash, remove and replace the mounting bushings, put it all back together, test that puppy and make it work as good if not better than OEM, and do it 2000 times.... well please send us your resume and advise us of any Par 6 courses in your area.
Rack Length Differences:
I should never write anything without having two cups of coffee and having my wife check my spelling and content..
YES, there are 2 differences starting with basically the "C" versions.
1) The shaft length went from 795 mm to 810 mm nominal, or about 1/2".
This does not affect the function of the steering from what we have seen, and you would adjust for the difference when setting the toe adjustment when you have your alignment done (a difference of 1/4" nominal per side).
2) There where 3 different designs of steering stops. The first two early versions are for the -22 or "B" early racks, and the last version is for the -24,26 & 27 or "C" and "D" models.
You need the correct steering stops. If you have an early
-22 or "B" version rack, check the integrity of the steering stops, the rubber
tends to degrade. On the later "C" versions they changed the stop to an aluminum
version. For you wide tire people we have heard of a "racer guy" out there who
doubled his stops to keep the tires from rubbing. You can use either version
rack in any year car, though be sure that your supplier is willing to allow and
exchange for different models (most don't).
And remember that the tie rod assemblies changed around 1987, (mid year 1986er's be aware).
Now, where did that cup of java go?