My wagon came with the 605 steering box from the factory. I very much like the 605 steering. It’s super smooth and light to the touch. It’s definitely not a “sporty” steering gear box.
My 605 started to leak around the top retainer ring only a few miles after the build. I found later than the newer GM steering pumps (2003) have a higher working pressure than the late 70’s pumps. This is very possibly the cause of my leaking. However, I didn’t know that I could simply swap the PS pump valves to lower the pressure.
I removed my fine but leaky 605 and tried to disassemble to replace the o-ring gaskets. I didn’t know what I was doing and messed up the disassembly by stripping the hexagonal adjustment screw on the sector shaft. Stripped and stuck half-disassembled, I decided to go with a new or rebuilt unit. I chose to upgrade the 605 to a 800 series quick ratio box.
I chose a rebuilt Saginaw 800 2 1/2 turn lock-to-lock gear box (Cardone 27-6550). All of the Saginaw 605 and 800 boxes were interchangeable, but different models of the 800 have different ratio gearing. This Cardone 27-6550 box is the same as the one found on Buick GN and Monte SS, and other sporty models (some Camaros and Jeeps also). This model 800 box requires a different pitman arm than the 605 as the output shaft is larger diameter than the 605 (and some 800s).
In switching out the steering box, I found that the previous 605 box used an inverted flare fitting while the newer box required an o-ring type connection. I previously switched out the fitting on my newer o-ring pump to the older style inverted flare so I could used the 1979 OEM high pressure hose to the 605. Now, I needed to switch it back to the original pump o-ring fitting to accept the newer (mid-80s) Gbody OEM o-ring high pressure hose.
Since I went through all of this to switch to a quicker ration gear box, I then decided to do the ol’ trick of swapping the steering shaft. This is desired by many to take the rag-joint play out of the steering. I chose the adjustable shaft of a 1990 Jeep Cherokee to replace the original Gbody rag-joint type steering. The rag-joint was still in excellent condition, but it was an easy, cheap swap/upgrade, so I did it. This swap is covered in detail in many places on the www, so I will only generally cover my install. VenomGT87 has a good video on the swap plus replacing the column bearing on his channel.
The shaft from the 1990 Jeep Cherokee is an adjustable shaft of sorts, in as much as it is two piece. While it is held together in a fixed position with plastic sleeves and some type of glue, it can be easily heated and pulled apart into two sections. If you wish, I suppose you could weld the shaft back together in the correct length for your Gbody, but I did not feel it necessary to do so.
The gear box end is a direct fit while the column end requires a slight modification. It requires that a slot or groove be filed or cut into the column shaft so the slip-on collar will accept the attachment bolt. It’s a pretty simple thing to do. Once you test fit it onto the upper and lower shafts, you simply mark the shaft where it needs filing. Remove the shaft, file your slot appropriately and reassemble using lock-tite on the fastening bolts.
Some who do this “LS swap” find that there may be some interference with the steering box and the power steering pulley. This can be resolved by changing the pulley. There are a couple options, but the most popular one seems to be using the Dorman 300-201 (plastic) or 300-202 (metal) pulley.
Compare the smaller pulley to larger truck pulley (installed) next to the 605 box. Clearance is similar to 800 Steering box. Shown is the OEM GM small pulley 10166335 (salvage yard pull) which is the same size are the Dorman.