PSC Steering: Poor return to center

mikalcarbine

mikalcarbine

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Joined
Dec 29, 2018
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82
Location
Arizona
I installed a PSC Extreme kit on my TJ a little over a year ago. I installed the box and test drove it prior to installing the ram and I noticed that the steering was very tight and wouldn't return to center, I could go into a parking lot and turn my wheel and do circles over and over or after a turn I'd have to "help" it return to center. This resulted in a highway drive where I'm constantly correcting the wheel back and forth.

I'm on 3" of lift with 35 MTRs @ 25psi, my toe in is about 3/16” and my caster is 4.5*-5*. Running OTK steering with a WJ knuckle swap. I even pulled from my front drive shaft and adjusted my caster all the way up to 7* and it didn't help.

PSC ended up sending me another gear, same thing happened so they sent me a third gear, same thing. At this point they recommended I back off the preload adjustment for the gear by 1/4 of a turn. I did this and it helped a little but my wheel would still not return to center like it used to. At this point I decided to give up and drive it for a while to see if breaking the gear in would help at all. Over a year later, being tired of how it drives on the highway I decided to retackle this once and for all.

I started backing off the preload of the gear by 1/8 turns and test driving it. This definitely helped but the return to center is still not 100%. In total I'm about 3/4 of a full turn "loosened" from how the gear was sent to me. Highway driving is markedly improved.

I gave PSC a call yesterday and their tech said the preload has nothing to do with return to center and he blamed my "extremely high" lift and caster as the problems and said that the weight of the jeep isn’t enough to drive the tires back to their center point. I told him my alignment specs are good and gave him the background on everything. He also sent me their procedure on properly setting the preload with the gear on a bench, something I'll probably try next.

They are willing to look at the box if I ship it in but I fear after 3 tries that it will come back the same way. I’ve seen a few other threads like this online, are PSC boxes just tight? Should I not expect 100% return to center? I’m tempted to buy a reman box locally to see if it exhibits the same problems.

Any thoughts?
 
The preload does have something to do with the return to center if it is to tight, that is why it got better when you loosened it. It might not be the overall problem but if the preload is to tight it will have that result.
 
mikalcarbine said:
I installed a PSC Extreme kit on my TJ a little over a year ago. I installed the box and test drove it prior to installing the ram and I noticed that the steering was very tight and wouldn't return to center, I could go into a parking lot and turn my wheel and do circles over and over or after a turn I'd have to "help" it return to center. This resulted in a highway drive where I'm constantly correcting the wheel back and forth.

I'm on 3" of lift with 35 MTRs @ 25psi, my toe in is about 3/16” and my caster is 4.5*-5*. Running OTK steering with a WJ knuckle swap. I even pulled from my front drive shaft and adjusted my caster all the way up to 7* and it didn't help.

PSC ended up sending me another gear, same thing happened so they sent me a third gear, same thing. At this point they recommended I back off the preload adjustment for the gear by 1/4 of a turn. I did this and it helped a little but my wheel would still not return to center like it used to. At this point I decided to give up and drive it for a while to see if breaking the gear in would help at all. Over a year later, being tired of how it drives on the highway I decided to retackle this once and for all.

I started backing off the preload of the gear by 1/8 turns and test driving it. This definitely helped but the return to center is still not 100%. In total I'm about 3/4 of a full turn "loosened" from how the gear was sent to me. Highway driving is markedly improved.

I gave PSC a call yesterday and their tech said the preload has nothing to do with return to center and he blamed my "extremely high" lift and caster as the problems and said that the weight of the jeep isn’t enough to drive the tires back to their center point. I told him my alignment specs are good and gave him the background on everything. He also sent me their procedure on properly setting the preload with the gear on a bench, something I'll probably try next.

They are willing to look at the box if I ship it in but I fear after 3 tries that it will come back the same way. I’ve seen a few other threads like this online, are PSC boxes just tight? Should I not expect 100% return to center? I’m tempted to buy a reman box locally to see if it exhibits the same problems.

Any thoughts?
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Unfortunately you got the new guy. I just checked for you and we still have it right. (do not do this without permission) Adjust the lash screw until you get some slight on center play and then tighten it back up slightly. That should improve the return to center to a tolerable level. You can also call into PSC and speak with Kelvin. He will check and see what the reports tell him about your previous gear box issues and get you squared away. Don't listen to the new guy.
 
Thanks Blaine! Your advice was on point, just spoke to Kelvin and he was very helpful and agreed with your method. For reference for anyone who might find this thread in the future, he recommended setting the preload with the wheels off the ground or preferably with draglink disconnected and engine off. Back the preload off until you can just start to feel the gears in the box “hit” each other when rolling over center and then tighten the box up a bit and give it a test drive. I’ll try this and report back
 
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Back the preload off until you can just start to feel the gears in the box “hit” each other when rolling over center and then tighten the box up a bit and give it a test drive
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Just like in the 70's and 80's....
 
Just for my own curiosity's sake, exactly what is your caster angle? I'm not saying the steering box isn't the main cause of the issue, just curious if a potentially insufficient caster angle could be contributing to the problem.
 
It should be somewhere between 4.5* and 5*, I'd need to pull up my last alignment sheet for an exact number. Measuring off the ball joint flat or lower c never gave me accurate measurements. I'll try to check tonight
 
mikalcarbine said:
It should be somewhere between 4.5* and 5*, I'd need to pull up my last alignment sheet for an exact number. Measuring off the ball joint flat or lower c never gave me accurate measurements. I'll try to check tonight
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Thank you. It's my opinion that the printout from the alignment rack is the only caster angle measurement you can truly trust. 4.5-5 degrees is right on the edge of being enough even for larger tires which generally require less caster angle for good return-to-center. Let's see what the printout says.
 
Jerry Bransford said:
Thank you. It's my opinion that the printout from the alignment rack is the only caster angle measurement you can truly trust. 4.5-5 degrees is right on the edge of being enough even for larger tires which generally require less caster angle for good return-to-center. Let's see what the printout says.
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Swing by some day and I'll measure yours for you and then you can have the alignment shop tell me how far off I am.
 
mrblaine said:
Swing by some day and I'll measure yours for you and then you can have the alignment shop tell me how far off I am.
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A competent individual such as yourself can obtain an accurate caster angle. Somehow the edit I did on that post accidentally removed the part that included that it's not easy to get an accurate caster angle. I wouldn't trust the caster angle I'd get with the knuckles installed/being in the way.
 
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mrblaine said:
Swing by some day and I'll measure yours for you and then you can have the alignment shop tell me how far off I am.
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When Blaine teases us about accurate caster measurements
2neebf.jpg


Seriously though, any tips to get it right?
 
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I’ll be installing the PSC extreme set up this weekend. Hopefully I don’t have the same issues
 
I hope it works out, I'm curious how the box handles for you, be sure to post here afterwards!

So I pulled out my last alignment sheet from about a year ago and my caster was 5.9* on the driver and 6.3* on passenger. This was with my front driveshaft removed when I was troubleshooting my return to center. When I got home I measured the flat spot on the front of my diff at 87* which equates to a caster of 6* based on the information that used to be on this site - http://go.jeep-xj.info/HowtoAlignment.htm (appears to be dead now). It basically stated for a HPD30, the caster angle is 9* offset from the pinion/diff angle when at 0*

1547821111189.png


I used this reference point to then set my caster to about 5.25 (86.25* on the diff) which is how it should be sitting right now. I'd like to verify this with an accurate method.

I searched around for accurate ways to measure caster. I understand that caster is the axis between the upper and lower ball joint in which the knuckle rotates on. I've seen methods that involve dowels inside the ball joint holes in the axle C's but that is not feasible in a situation with everything installed. I stumbled across one of Blaine's posts on another forum

Caster is the inclination of the king pin axis. In other words, draw an imaginary line from the center of your top balljoint extending through the center of you lower balljoint. That the axis or pivot point that the knuckle rotates around.

If you know that, then some simple knowledge about machine processes and deductive reasoning will allow you to pick a few places to use an accurate angle finder. The lower balljoint has a nice flat spot on it. The upper has a nice shoulder where it rides against the top of the inner knuckle. They are both at right angles to the centerline due to the way they are machined and make good places to measure caster from.

What confuses folks about trying to measure it, is that it they also lean inwards making most pendulum style angle finders useless unless held perfectly vertical.

Do not use any welded on brackets to determine caster if it's important to what you are doing. They are not that accurate."
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I have a digital angle finder and I've tried using the lower ball joint flat in the past without luck but will try agian this weekend. In theory the lower ball joint flat should match the upper ball joint shoulder right? This should be a good way to verify my measurement
 
Played with the preload of the steering box tonight. It was hard to feel anything through the steering wheel while loosening the preload so I resorted to loosening a bit and test driving, repeat. I got the steering pretty sloppy and the return to center still wasn't 100%, after taking a corner I still had to help it out the last bit before it'd center and while driving I can "aim" it one way or another and it'll track that way.

I was able to get some good readings from the ball joints for my caster that coincides with my previous measurements. It should be right around 5.25* right now. I also pulled my tires and double checked my alignment using aluminum stock, was right at 1/8" for 28" tire. I pulled it into 1/16" and it didn't make any difference.

I also disconnected my temporary steering stabilizer (I use this when the hydro ram isn't installed) and while my draglink was disconnected the knuckles both rotated freely

One of my last resorts might be picking up a reman box so I can 100% eliminate any other possibilities outside of the PSC box. I'll be giving Kelvin at PSC a call on Monday.
 
Spoke with Kelvin, even though the box is slightly out of the warranty period they'll be covering any work that needs to be done on it, will be shipping it out to them soon. Great customer service, hopefully they can get it right this time. @Rescue6 how did your install go?
 
mikalcarbine said:
Spoke with Kelvin, even though the box is slightly out of the warranty period they'll be covering any work that needs to be done on it, will be shipping it out to them soon. Great customer service, hopefully they can get it right this time. @Rescue6 how did your install go?
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Amazing customer service. I'm pretty sure most places would have told me to pound sand and the problem was on my end after box number two. Not quite sure how you are convincing them that it is their box - kudos to you.

So, this begs the question, assuming the problem is actually PSC, how 3 bad or poorly set up steering gears could leave their shop. Doesn't instill much confidence.

Looking forward to their findings.

Sent from my SAMSUNG-SM-G930A using Tapatalk
 
mikalcarbine said:
Spoke with Kelvin, even though the box is slightly out of the warranty period they'll be covering any work that needs to be done on it, will be shipping it out to them soon. Great customer service, hopefully they can get it right this time. @Rescue6 how did your install go?
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Still sitting in the garage. I’ll let you know when I’m done with it. Threw my back out. When removing all the old steering. I’ve had five back surgeries in the last few years so unfortunately it’s common place nowadays. Sometimes what normally would take a few hours takes me a few days or weeks unless I get a buddy to come help me.
 
superduty said:
Amazing customer service. I'm pretty sure most places would have told me to pound sand and the problem was on my end after box number two. Not quite sure how you are convincing them that it is their box - kudos to you.

So, this begs the question, assuming the problem is actually PSC, how 3 bad or poorly set up steering gears could leave their shop. Doesn't instill much confidence.
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He asked me a few questions, mostly about caster and if the knuckles moved freely when disconnected from the box. He said with the ram installed they like to see closer to 6*-7* of caster but I explained I had removed the ram for troubleshooting. Not sure how any lifted TJ's could hit 6*-7* without vibrations without having the C's cut off and spun

Rescue6 said:
Still sitting in the garage. I’ll let you know when I’m done with it. Threw my back out. When removing all the old steering. I’ve had five back surgeries in the last few years so unfortunately it’s common place nowadays. Sometimes what normally would take a few hours takes me a few days or weeks unless I get a buddy to come help me.
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Sad to hear that, wishing you a quick recovery!
 
Thanks. Just something I live with at this point. I’ll wind up with a few more surgeries before it’s all over but. Some good days some weeks I spend more days laying down than upright. I can stand up all they way strait again and sit for more than a few minutes at a time not to mention walk without a walker. So it’s all perspective. I’m a hundred times better than I was two years ago but no where near as good as I was seven years ago. I’m not going to let it stop me from enjoying life every chance I get. I may not be able to be a Firefighter anymore or ride and race dirt bikes anymore but I love the freedom the old Jeep allows me to have and get out away from everything and everyone to explore
 
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