power steering swap

[hpcgmc]

As I wrap up my suspension/brake project, I'm looking at the power steering project. I thought I could just buy a kit, similar to the disc brake kits, but no luck, so it's off to the junkyard I go.

Is there a certain year that works better then others, or do I just look for any 73-87 truck? I've read that it's important to get all the brackets, pulleys, etc from the same vehicle, so I'll do that. Will I need any parts after the steering box (between steering box and the wheels)?

Once I get all the used parts, should I look into a new steering box and ps pump? It's a bunch of extra cash, but I don't want the used parts failing in a year or two.

[airdale94]

There's a cutoff year on the ps gearboxes, GM went to metric fittings. I believe it's 79 or 80. What I would do is get the pump, hoses, and gearbox new. And get the brackets and pulleys salvage. Unless you find a nice fairly low milage truck, then get everything.

There will be core on the pump and gearbox new anyway so you will recoope some of the salvage price.

[71Dually]

73-79 are SAE flare type fittings, 80-86 C series trucks & 87-91 R series trucks are metric O-ring type fittings.

The research I've done on the PS steering gearboxes is that in their respective years the 10, 20 and 30 series boxes are all the same part numbers per factory master part catalogues so they should interchange. This gives you the opportunity to look at different series trucks and increase the number of potential candidates in the junk yard.

Be careful with the 87-91 models, there were R series and C series trucks. In 1987, with the upcoming 1988 introduction of the new GMT400 truck line, the older C series truck design was changed to the R series and the upcoming GMT400 trucks were then designated as the C series. This designation is actually found in the VIN rather than the body emblems. A simple way to visually identify them is the GMT400 trucks have upper door edges that go flush into the roofline (no drip rail), the bottom edge of the door extends to the lowest part of the body to allow a lower step up entry and the windows are flush with the outer frame and door skin.

A little further information regarding the 87-91 R series trucks. From what I have gathered here on the forums the general consensus for interchange seems to be that the cutoff is 1986. From my research I have found that to not be the case with the steering components you are concerned with. According to Wikipedia, 1987 was the only year for the R series conventional cab, all 88-91 R series trucks are reported by Wiki as being dually crew cabs. The master part catalogues show part #7846958 PS gearbox listings for R10, 20 and 30 series trucks from 87-91 so this kind of conflicts with wiki unless they made a R10 dually crew cab which I doubt. My bet is the info in the master part catalogues may be more accurate than wiki but errors are possible. However, both sources do reveal the R series trucks were built from 87-91 and the part catalogues show all these R series trucks used the same PS gearboxes as all the earlier 80-86 C series models. Just check the 87-91 doors and drip rails and avoid the GMT400 trucks and you should be fine with interchanges to the earlier pre 87 models.

Here are some C & R series GMPartsWiki PS gearbox links showing the match: here, here, here, here, here, here, here, and here.

On a side note for those who would like to know, I have found that in addition to the steering gearboxes the spindles and brake calipers for the C30/R30 JB8 brakes are exactly the same parts on both the 80-86 C series and the 87-91 R series trucks. This points to other interchanges from these later 87-91 R series trucks to earlier models also.

Continuing on topic. Since your doing a whole setup it won't matter if you use either the earlier SAE flare or later metric O-ring fittings, just a matter of personal choice. Something to consider however is that 80-91 parts will probably remain in aftermarket production longer than the 73-79 parts and may remain easier to get "over the counter". Just keep within the same year periods to keep everything simple.

If your junkyard part availability is limited, mismatched metric and SAE fitting pumps and gearboxes can used but you will need to adapt. Some folks run adapters or make custom hoses. These can be expensive and/or create extraneous work and are not necessary. The simplest fixes I've found for these mismatches are to swap out the rear outlet pressure fitting on the PS pump to match the gearbox fittings or get some metric O-ring to SAE flare fitting "inserts" to put in the gearbox. These "inserts" are not the same as the fitting "adapters" and give a much cleaner installation. I'm looking for where I found the inserts but I'm not having any luck at the moment. I'll post up a link when I do re-find them. Thanks and all credits go to TX Firefighter for the PS pump rear fitting swap in the topic here. See post #5.

I don't know what will be necessary to mount the PS gearbox on a non-PS truck frame. I have never done a 67-72 PS retrofit but I've read in this forum for earlier non-PS trucks you need to dimple the frame to achieve clearance for the PS gearboxes sector or input shaft, not sure which shaft. The mounting holes I understand are exactly the same. Perhaps someone who has done this retrofit will provide further knowledge on this. You can search the forums for power steering conversions and should find lots of information.

I have also seen forum posts regarding steering coupler retrofit which could be pertinent to your project. While I read the information I didn't pay to much attention to the details because I'm doing a hydroboost retrofit on my 1971 C30 and already have PS in my truck and the coupler info wasn't pertinent to my project. Again search the forums and perhaps someone may also provide further knowledge regarding the couplers in this topic.

Another area of concern is the steering pitman arm. You may have to swap all the steering linkage (centerlink, tie rods etc...) to use a later 73-91 PS gearbox. This may apply to the 71-72 gearboxes also. I'm not trying to scare or discourage you on your upgrade as it is totally doable. I'm just giving you a heads up about these areas of potential differences. Again, like the coupler, I'm not real sure about all the details of the pitman arm as it didn't pertain to my 71 C30 project either. But, like the coupler, I recall observing this information in forum posts regarding the earlier truck gearbox swaps to the later 73-91 gearboxes. I don't know the parts you have used or how you have done your suspension/brake upgrades but this information is pertinent to a steering upgrade and the PS pitman arm.

If possible please post up what you have done with your suspension/brakes and the parts you've used. The steering knuckles (aka spindles) in particular are pertinent. That will keep everything matched up and assist the forum membership in helping you successfully complete your PS project.

One last heads up, watch out for the PS pumps on hydroboost trucks, they sometimes have two return lines on the reservoir. PS only pumps use only one return line. Sometimes the hydroboost pumps did use only one inlet but those setups ran the return lines from both the steering gear and brake booster into a tee fitting to accommodate the single inlet on the pump reservoir. Just something to look out for in your junkyard part search.

Originally Posted by airdale94

What I would do is get the pump, hoses, and gearbox new. And get the brackets and pulleys salvage. Unless you find a nice fairly low milage truck, then get everything.

There will be core on the pump and gearbox new anyway so you will recoope some of the salvage price.

I agree with airdale94 on this point. Your trucks steering is a very critical component. Compared to used parts, fresh components will provide increased longevity, superior stability and a much more comfortable and safer ride.

Hope all this helps.

Good luck with the project and please keep us posted about how it's going and how it all works out. Please don't forget the pictures.

Cheers