grease fitting on power steering

[Jim S.]

Re: grease fitting on power steering

I have gotten out all of my Valve & Adapter Assembly drawings and reviewed them. I now believe that I made some incorrect conclusions regarding zerk fittings and ball stud seals.

I have a Valve & Adapter Assembly drawing 7825636 which indicates its first useage as the 1976 Corvette. (Drawing date was 11-20-74 and Engineering Release date of 3-12-75). I believe that it is the latest and last valve & adapter part number for the C3 Corvette. I don't think that Joe Lucia's records indicate any later valve part numbers.

This drawing has revisions as late as 1-25-88 so it was kept up to date through the years. It shows a zerk fitting and a purge slit in the ball stud seal nipple with no revisions throughout its drawing life (1974-1988). This would indicate that the zerk fitting was never eliminated from the valve.

Also, I have an early valve & adapter drawing (5691955 dated 7-11-62) which also shows a Zerk fitting. That same drawing shows a ball stud seal revised and a purge slit added 2-19-75.

So from the above information, I am led to the following conclusions:
1). Zerk fittings were always installed on the adapter, (even if the valve was "greased for life"). Possibly the Zerk was needed to fill the ball stud cavity (either at Saginaw or possibly at St. Louis/Bowling Green?).

2). Valves before 1975 did not have the purge slit in the ball stud seal. I now believe that the purge slit may have been added to act as a pressure relief valve (it allows excess grease to escape and prevents high pressures from damaging the valve seals.) The purge slit may not have had anything to do with "greased for life" edicts from General Motors.

BTW, here are engineering revision dates for some other valve changes. (The revision dates are not necessarily production dates.)

Stamped "C" eliminated from the end cap (Revision A dated 7-20-77).

Two bolts that attached the valve to the adapter changed from 180123 (12 point) part number to 178940 (hex), (Revision C dated 3-20-79).

Jim Shea

[Michael J.]

Re: grease fitting on power steering

The original control valves had a zerk fitting and a ball stud boot with a purge slit to allow excess grease to leak out of the boot. This boot design was very good in that you could not overfill the ball stud cavity. The excess just regurgitated on the floor.

During the 1970s there was a concerted move on the part of GM to have all their cars with "lubed for life" tie rod ends, ball joints, and other chassis fittings. The Corvette control valve was included in the edict. So I assume the control valve was packed with a better grade of grease, the purge slit was eliminated, and the zerk fitting removed.

Now the problem arises with rebuilt control valves. A lot of cores have zerk fittings. I am quite sure that the ball stud boots all come without purge slits. So I am equally sure that a lot of rebuilt control valves are overfilled with grease because they come equipped with a zerk fitting. Worse, the grease has no place to go but back against the hydraulid seals in the valve, or the excess causes the ball stud boot to burst.

Jim

My PS has no grease fitting where this diagram shows, it is on the end of the unit, the "ram". Is that one different in design?

[Jim S.]

Re: grease fitting on power steering

Yes, there is a short Zerk fitting on the end plug part of the assist cylinder (Ram) ball stud that connects to the relay rod.

Jim

[John H.]

Re: grease fitting on power steering

Most, if not all, rebuilt valves have an "off color" grease in them. If they find any other grease in them most vendors will deny warranty.

Every rebuilt control valve I've bought (usually Lone Star) came with a card saying the warranty was void if you greased the zerk; later ones came with a steel plug in the hole and no zerk.

[Joe L.]

Re: grease fitting on power steering

I have a Valve & Adapter Assembly drawing 7825636 which indicates its first useage as the 1976 Corvette. (Drawing date was 11-20-74 and Engineering Release date of 3-12-75). I believe that it is the latest and last valve & adapter part number for the C3 Corvette. I don't think that Joe Lucia's records indicate any later valve part numbers.

Jim Shea

Jim------


Yes, the 7825636 was the last part number for the control valve. In fact, it's still available from GM under that number (for about 650 bucks, GM list).