1997 Suburban Steering Issues

[tommywass]

I'll check out the binding by taking off the tie rod ends. The wheels turn freely when I jack up the front and turn them by hand.
After some more research I'm really starting to think it's an issue with the EVO steering system. If any of you really know that system and how to diagnose issues with it please let me know! My theory is that I have full steering pressure all the time, which is why the wheel is so easy to turn and the caster is not always enough to center the steering after a turn. I've heard it referred to as "easy steer" in my research. It sounds like most people opt to remove the system and still end up with overly "easy" steering. I'd really prefer to try to fix my system and deal with the EVO issues as they come (probably having to use sensors out of the junkyard because they're not produced anymore).
So far I've replaced the solenoid valve on the back of the PSP with a junk yard part with no change. I don't know how to test the valve though.

 

[Joseph Garcia]

Years ago, I had a steering issue suddenly pop up on my 1997 Yukon SLE. When driving at speed, if I nudged the steering wheel to the left, nothing would happen, and my Yukon would continue going straight. When I nudged the steering wheel a bit more to the left, the Yukon would suddenly lurch to the left, really to the left, and veer into the next lane. Definitely not safe.

I blindly ended up changing the steering box, the power steering pump, the pitman arm, and the idler arm in succession, and my issue did not resolve.

I finally found an EVO system bypass assembly, sold by GM (clearly, GM knew that this particular rendition of this feature was a failure), and I installed it, and my steering issue was resolved. As I recall, it was a simple steel tube with the correct fittings on each end to bypass an electric solenoid connected to the power steering pump and one of the power steering fluid lines. It cost me about $80 from GM, but I could have fabricated it myself for about $10.

I don't know if this has relevance to your issue, but I thought that I'd throw it out there.

 

[tommywass]

Thanks Joseph! That is very relevant to my issue. That's the fix I know most people would suggest. I'm a bit worried because I've read mixed reviews on the bypass. Some say the steering feels loose or "easy." What was your take on how it felt after you bypassed it? I know that everyone has their own opinion on how steering should feel but I'm curious what you thought.

 

[exp500]

I was going to suggest EVO- but the way you described the issue it doesnt fit. My EVO fix was to Replace Power steering pump and pressure line. I used a 96 as components, left the EVO valve plugged in behind the pump,then tywrapped to the bundle out of the way. That prevents EVO codes. I also re-shimmed the pump relief valve to drop the pressure 200 lbs as I'm really picky as how my stuff drives. (I want road feel). I've done this for 3 trucks so far, no codes,complaints, call backs. I do suggest buying a new pump pulley- it seems to me to be about 50/50 chance of destroying it on removal, and I like the one with holes in it so ya don't have to remove pulley to remove pump. I also like Lares rebuilt. (never a problem-Yet). Then you can focus on alignment. There is a 4x4 shop nearby that has been recommended for alignment that I haven't tried.( the 5 that I have tried all suggested repairs that were unnecessary and did alignments by changing toe and ride height, worst one was 2" different L/R.) Been doing my own for last 3/4 years- it works well but takes alot of time to get perfect.

 

[Joseph Garcia]

Thanks Joseph! That is very relevant to my issue. That's the fix I know most people would suggest. I'm a bit worried because I've read mixed reviews on the bypass. Some say the steering feels loose or "easy." What was your take on how it felt after you bypassed it? I know that everyone has their own opinion on how steering should feel but I'm curious what you thought.

The steering was a tad bit less responsive for very small movements in the steering wheel, which was the original intent by GM to improve, with the EVO feature. But, for any larger turns of the steering wheel, I did not notice any difference at all.

For me, it did not make the truck any less driveable, and it made it a whole Hell of a lot safer to drive.

 

[tommywass]

Thanks guys.
I've done some research on both of those options. exp500, what's the reason you used a pump and pressure line off a '96? I thought the '96 components didn't have EVO, but you mentioned still plugging into the EVO valve behind the pump. (maybe you meant a '96 steeeing gear??) Would you mind clarifying a little? Because I'm suspecting my EVO valve isn't working anymore, could I just shim my existing valve in the '97 pump? I do like the idea of being able to adjust the assist by using shims until I get the feel that I like.

 

[exp500]

The EVO valve is a solenoid valve- on is full pump flow/pressure.(thats why steering gets jerky)EVO Valve is on back of p/s pump pressure port. EVO sensor on steering column under hood. The GM bypass kit is a p/s pump fitting on a tube that threads into pump in place of EVO Valve. ($60.00) The 96 power steering hose does the same thing. Any reman pump you get usually comes with a bypass BTW. Just cannot buy them seperately except thru GM. Shim kit Bill's Hotrod P/N 1001.Shim kit adjusts pump relief valve. Maybe Jegs Has it too. Don't go too low on pressure or parking is a squealing pump and hard steering. Sometimes 850# is enough. Tires/wheels change the numbers. Remember everything goes thru computer? Computer controls EVO valve? Leave valve Connected doing nothing.( remove pump, remove valve from pump). If you want to keep your pump you need a relief valve assy.(junkyard) any GM style 80's-90's threads in.

 

[tommywass]

Update: I got a shim kit and a '96 high pressure line. Before I install them, I had a thought which I haven't mentioned on this thread (I thought they were unrelated until now). My cruise control went out about the same time that I noticed the steering over-pressurization. What if they're both getting a bad speed signal from the VCM/ECM (I think they're all one computer). The speed sensor on the transfer case seems to be fine because the speedometer works and the tranny shifts. But what if the speed output, when it comes out of the computer to the EVO steering and the cruise is not good? Then I think I may get all the symptoms I'm experiencing. When I test the speed input prong on the plug that goes into the cruise control module, I'm not getting the results I think I should be getting (according to a YouTube video). All that being said, does anyone know how to test the speed output of the the ECM to make sure the steering (and cruise) is getting the signal it needs? I'd like to confirm that before I start trying to shim the pressure valve in the pump.

 

[wjburken]

Update: I got a shim kit and a '96 high pressure line. Before I install them, I had a thought which I haven't mentioned on this thread (I thought they were unrelated until now). My cruise control went out about the same time that I noticed the steering over-pressurization. What if they're both getting a bad speed signal from the VCM/ECM (I think they're all one computer). The speed sensor on the transfer case seems to be fine because the speedometer works and the tranny shifts. But what if the speed output, when it comes out of the computer to the EVO steering and the cruise is not good? Then I think I may get all the symptoms I'm experiencing. When I test the speed input prong on the plug that goes into the cruise control module, I'm not getting the results I think I should be getting (according to a YouTube video). All that being said, does anyone know how to test the speed output of the the ECM to make sure the steering (and cruise) is getting the signal it needs? I'd like to confirm that before I start trying to shim the pressure valve in the pump.

There are a few reasons that your cruise could have gone out and the timing maybe a mere coincidence. Check to make sure all your brake lights work. GM has a habit of disabling cruise if the vehicle senses a burnt out taillight/brake light as a way to let you know. Also check you brake light switch. Not sure about your generation of vehicle, but on the GMT900’s that switch has been the cause of many a cruise controls to not work.

I’m not saying you don’t have a problem with the modules as you mention, but I’d check some of the more simpler, more common causes of cruise not working before you go down the path of testing/replacing a module.

 

[exp500]

EVO not part of cruise system. Cruise boxes fail alot! As long as you are not having trouble with the combination switch- turn, 4ways, horn ect. then probably cruise box. 40-50$ junkyard. Cruise testing box is dealer only. Swap in your buddies known good box for a day. Trere are a few threads on cruise box they are all interchangeable I think.