I've searched the archive to no avail, but I could have sworn that not too long ago someone (Bent1 maybe?) mentioned something about synthetic power steering fluids possibly having a greater tendency to leak than traditional fluids?

I rebuilt a spare power steering pump this last week and installed it in on my mom's 99 Tahoe. Her original PS pump had 125,00 miles on it and had an appreciable leak from the front shaft seal area. I had switched this truck over to Redline PS fluid when it was new, and had changed the fluid at regular intervals as part of maintenance. Thinking back, it seems like I've developed leaks from this same spot on my own truck several times as well. I've seen some boxes on other cars going 200,000 miles without leaking, having never had the fluid changed from the factory stuff. Aside from my questioning as to whether or not there is any validity to the whole synthetic fluid contributing to leakage theory, I have to say the insides of a pump which runs the Redline stuff looks REALLY good in terms of wear. I intend to rebuild her old PS pump and put it on my own truck.

As part of this project, I deleted the EVO solenoid, but instead of using GM's adapter to do so, I just put on all new lines from a 96 model. I also installed the GM factory cooler and a Magnefine filter on the return hose. Lastly, the fluid is doped with about 1 teaspoon of MoS2 powder. The steering feel is excellent. Having the twitch gone is a huge improvement and the feel in terms of stiffness in turning the wheel is really no different than with the EVO system intact. I had expected driveway/parking lot maneuvers to require more effort, but I have to say there really is no appreciable difference at all.

Don't know about that, but switching to synthetic MOTOR oil can cause leaks on an engine with 100K plus miles due to its cleaning properties. Over time and heat cycles the gaskets would wear, oil would get in and form its own seal by drying in and varnishing up. Synth poured into the engine would clean these deposits out causing the engine to start leaking. I doubt this will be a problem with the new style seals they have though. I could see something similar happening with a PS pump that was using a regular fluid that was switched to synth.

Is the steering feel any different from a stock 96 system compared to say a 92-93 tbi™ truck? I found my 1992 rcsb TBI350 to be very stiff.

Glad you aren't as twitchy anymore. I find it much more confident to drive.

peace
Hog

Sorry, Hog... haven't been keeping up with posts too well this week. New semester started, so school has me up against a wall right now.

I had a 93 model truck years ago, and the steering on that truck and my 96 model always felt the same to me. So, I don't know if I can really comment fruitfully on that issue between the 96 and older tbi™ trucks.

As far as the feel of the 96 system, I can't really compare. My 96 pickup seems a bit stiff, and I'm guessing it's due to the relatively fat 275/60/R15 Radial TAs I run on it. I actually took the pump off of my 96 truck and put it on this 99 4wd Tahoe... and the steering is really easy on the Tahoe with that pump, with no changes to the flow valve or anything else. Incidentally, I also ran 275/60/R15 Radial TAs on my old 93 model (mentioned above) as well.

Actually, the steering is barely (and I mean BARELY) any stiffer than before with the EVO. Parking lot maneuvers and backing out of the driveway are the only place I noticed just a slight increase in effort, but my mom actually couldn't tell any difference in effort when I brought the truck back to her. The steering is really easy, a little too easy for my taste up on the highway, but she likes it.

I'm actually looking into pulling the flow control valve back out and adding some shims to the adjuster... this is supposed to lower the pressure and give a better road feel... have been doing a ton of reading up on this online. Would like just a bit more resistance, but I'm not going to go crazy with it. Incidentally, one can also adjust the nut tighter on the flow control vale to give more assist if needed. Might be worth looking into if you don't like the stiffness of the post-EVO setup.

As far as I'm concerned though, the retrofit from the EVO setup back to 96-model spec was a huge success. I highly recommend to anyone that they buy the $20 96-model high pressure hose, take the EVO solenoid completely off the existing pump, add the 96 flow fitting, and go. I prefer it, personally, over the idea of the add-on fitting.

I agree I had pumps laying around stole a fitting from one and bought the 96 lines all at the same time as doing a hydroboost swap. I actually think my truck drives and feels alot tighter at highway speeds with it bypassed and at slow speeds I didnt notice anything different.

Just wanted to add this into this old thread so it's here for reference:

Something I just discovereed while messing around with EFILive... deleting the solenoid will not trip an MIL or cause any issues at all, but it does show up as a fault code when you scan the VATS module, as that is what controls the EVO solenoid (EFI Live can scan this module, but I've not been able to do so with HP Tuners). I have a screen shot I have been meaning to post about this, but have not had a chance to do so. I plan to measure the resistance of the old EVO solenoid and wire a resistor in place to get rid of the code on the 99 Tahoe I did this conversion on.

EDIT:

Just looked up my screen shot from EFILive. Here is the info:

DTC = C0503 - Steering Assist Control Solenoid/Motor/Actuator Return Circuit Low (Status HC)

Module: ($C0) Theft Deterrent Control Module (VTD)