Poor return to center with PSC steering

[mrblaine]

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*

View attachment 72863

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



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

We take a piece of 1/8" thick flat stock that is 2" wide and about 6" long. Set it on the machined flat spot just inside the lower ball joint on the bottom of the inner C. Put the angle finder on the flat bar, feel for it to get flat against the flat spot, read the angle making sure that the angle finder is pointed nicely front to back. That will get you very close every time. There is a difference in angle side to side for cross caster to combat road crown.

 

[mikalcarbine]

We take a piece of 1/8" thick flat stock that is 2" wide and about 6" long. Set it on the machined flat spot just inside the lower ball joint on the bottom of the inner C. Put the angle finder on the flat bar, feel for it to get flat against the flat spot, read the angle making sure that the angle finder is pointed nicely front to back. That will get you very close every time. There is a difference in angle side to side for cross caster to combat road crown.

Thanks for sharing, that's basically what I did. For the upper I rotated a piece of cold rolled 1/4"x1" stock and put it against the machined shoulder of the joint. I might buy a piece of tube with an ID that matches the ball joint that rests on the shoulder. That would give a nice flat and stable base to rest the angle finder on, making the measurement a little easier and consistent.

 

[mrblaine]

Thanks for sharing, that's basically what I did. For the upper I rotated a piece of cold rolled 1/4"x1" stock and put it against the machined shoulder of the joint. I might buy a piece of tube with an ID that matches the ball joint that rests on the shoulder. That would give a nice flat and stable base to rest the angle finder on, making the measurement a little easier and consistent.

You can't measure any angle by using any part of the ball joint itself unless you have a very accurate method to ensure the front to back alignment of the angle finder is perfectly parallel to the centerline of the rig.

The ball joints lean. If you use them to measure caster the angle reading will change as you move the finder and point it different directions. The only place I've been able to find near the ball joints where that can't happen is against the cut in the lower part of the inner C where the nut is.

 

[mikalcarbine]

You're talking about this circled spot right? (JK Dana 30 inner c shown, I think the TJ Dana 30 is similar just not as sharp)



Would this would be parallel with the center line of the vehicle assuming that the axle has been squared properly and the tubes aren't bent? I can't find any good photos to reference right now but isn't that also near the machined "lip" of the lower BJ? I wonder if a jig or properly sized piece of steel could be selected to give you ball joint angle for caster from while maintaining a forward position parallel with the center line of the vehicle from the cut edge of the inner c

 

[mrblaine]

You're talking about this circled spot right? (JK Dana 30 inner c shown, I think the TJ Dana 30 is similar just not as sharp)

View attachment 73614

Would this would be parallel with the center line of the vehicle assuming that the axle has been squared properly and the tubes aren't bent? I can't find any good photos to reference right now but isn't that also near the machined "lip" of the lower BJ? I wonder if a jig or properly sized piece of steel could be selected to give you ball joint angle for caster from while maintaining a forward position parallel with the center line of the vehicle from the cut edge of the inner c

Yes, shove the spacer over against the flat and that will be parallel to centerline of vehicle. It is a very sharp clean corner to work with.

 

[mikalcarbine]

PSC rebuilt my box and said everything looked good. I received it and just installed it yesterday, same steering issues exist. I haven't played with the preload on this box yet.

When everything was apart I double checked that the knuckles move freely and paid special attention to how they felt near center and everything was very smooth.

I'm really at my wits end now, is there anything else I should be looking at?

 

[superduty]

If psc rebuilt it and checked it why would you need to mess with the preload?

Are all your tests being done with the ram installed?

Were any other changes or parts swapped out when you installed the psc components? Tie rod, etc?





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[mrblaine]

PSC rebuilt my box and said everything looked good. I received it and just installed it yesterday, same steering issues exist. I haven't played with the preload on this box yet.

When everything was apart I double checked that the knuckles move freely and paid special attention to how they felt near center and everything was very smooth.

I'm really at my wits end now, is there anything else I should be looking at?

I'm not entirely sure what it going on but after 4 steering gears from PSC including this rebuild, I'm going to suggest it isn't the steering gear. I do know that some folks are very sensitive about RTC and fully expect more than they will ever get. Just went through this exact thing with a bone stock TJ Unlimited Rubicon. His complaint other than DW for the last 75,000 miles was a poor return to center doing a U turn. We drove it and the RTC was well within any expected amount for normal driving. If you are expecting it to turn back to straight on a normal 90 degree turn, that ain't ever gonna happen without you helping it.

 

[mikalcarbine]

If psc rebuilt it and checked it why would you need to mess with the preload?

Are all your tests being done with the ram installed?

Were any other changes or parts swapped out when you installed the psc components? Tie rod, etc?
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Their preload from their shop seems to be tighter than what I need, I don't know if this is because the kit is for 37"+ tires and I'm running 35's? All my recent testing (this entire thread) has been without the ram installed.

I'm not entirely sure what it going on but after 4 steering gears from PSC including this rebuild, I'm going to suggest it isn't the steering gear. I do know that some folks are very sensitive about RTC and fully expect more than they will ever get. Just went through this exact thing with a bone stock TJ Unlimited Rubicon. His complaint other than DW for the last 75,000 miles was a poor return to center doing a U turn. We drove it and the RTC was well within any expected amount for normal driving. If you are expecting it to turn back to straight on a normal 90 degree turn, that ain't ever gonna happen without you helping it.

That's been in the back of my head for a bit, this isn't my DD so I'm constantly trying to remind myself that it won't likely behave like my stock truck in many ways. Honestly the RTC after a 90* turn doesn't both me, its more the lack of correction on the street and highway, I can aim the wheel left or right and it'll continue to track that way. Most other vehicles will snap or pull the wheel back to straight after a correction. Is this normal? Maybe I need to get in a few of my buddy's TJs for comparison.

 

[mrblaine]

Their preload from their shop seems to be tighter than what I need, I don't know if this is because the kit is for 37"+ tires and I'm running 35's? All my recent testing (this entire thread) has been without the ram installed.

No, that is YOU trying to make something do something it isn't supposed to do. It isn't tighter or looser than what you do or don't need, it is usually as tight as the steering gear is supposed to be to get the gear lash correct. Had you never known of or adjusted the damn thing, you would never think that.

That's been in the back of my head for a bit, this isn't my DD so I'm constantly trying to remind myself that it won't likely behave like my stock truck in many ways. Honestly the RTC after a 90* turn doesn't both me, its more the lack of correction on the street and highway, I can aim the wheel left or right and it'll continue to track that way. Most other vehicles will snap or pull the wheel back to straight after a correction. Is this normal? Maybe I need to get in a few of my buddy's TJs for comparison.

I don't know of any TJ that I have ever driven that snaps back to center after a correction. That is the entire point of the steering wheel, it gives you some way to have the vehicle go where want it to using your hands. It isn't supposed to steer itself.

Every vehicle I have ever driven generally won't go perfectly straight or correct itself back to straight. Being one of those that spent many years pouring myself cups of coffee into a cup set on the center console, I'm very familiar with how straight something does or doesn't go when I don't have my hands on the steering wheel.

 

[superduty]

What kind of tires are you running?

What condition are they in?

How old are they?

How old are ball joints? The highway stuff sounds like balljoints.

The highway stuff I refer to is from your wallet message where you say you are constantly correcting. Which is different from what you are describing now...snap back.

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[Mr. Bills]

. . . this isn't my DD so I'm constantly trying to remind myself that it won't likely behave like my stock truck in many ways. . . . Is this normal? Maybe I need to get in a few of my buddy's TJs for comparison.

Instead, you might want to have someone drive your jeep who doesn't know anything about your return-to-center concerns or your history of chasing a steering issue in order to get an unbiased reaction from them.

Then go drive other people's jeeps - one with stock steering or nothing more than a Currie Correctlync setup and another jeep with ram assist steering, preferably one with a PSC ram and steering box.

Those two road tests from two different perspectives should minimize or at least counterbalance any inherent bias in your butt dyno.

 

[afusco1222]

Their preload from their shop seems to be tighter than what I need, I don't know if this is because the kit is for 37"+ tires and I'm running 35's? All my recent testing (this entire thread) has been without the ram installed.



That's been in the back of my head for a bit, this isn't my DD so I'm constantly trying to remind myself that it won't likely behave like my stock truck in many ways. Honestly the RTC after a 90* turn doesn't both me, its more the lack of correction on the street and highway, I can aim the wheel left or right and it'll continue to track that way. Most other vehicles will snap or pull the wheel back to straight after a correction. Is this normal? Maybe I need to get in a few of my buddy's TJs for comparison.

I'm going to revive this old thread because I am experiencing something very similar. I have just recently swapped from the Mercedes Box to the PSC hoping to not have a dead spot in my steering wheel. The Jeep drove great before and I was experiencing no steering issues prior. After the box swap, and just like @mikalcarbine, after I turn the steering wheel left or right the Jeep holds its line and I have to use a lot of effort to get the Jeep pointing straight. My TJ has a 4" of lift up front, and I'm running a HP30 with 0 degree difference between the pinion angle and the driveshaft, so caster was an issue. I lowered the pinion 1.5 degrees and the steering got better, but if I turn the steering wheel to the 2 o'clock position, the Jeep will hold that line and would put me into a curb. Has anyone solved this problem with PSC or is this normal for the PSC boxes?

 

[mudmaster]

I've had the same PSC box for 3ish years. It works without any of these issues on the HP 30 it had and the current HP 60.

 

[afusco1222]

I did a little more digging into my setup. First I contacted PSC and this is the response I got.

Fair enough. I contacted my 4x4 shop that did my alignment a couple of weeks ago and I got my Caster numbers. 7.3 degrees and 6.8 degrees. I am running 34" tires and am well within their specified spec. Since that alignment, I have lowered my pinion angle putting it now at 8.8 and 8.3 degrees with a 1.5 degree of separation between the pinion angle and driveshaft. I have no vibes at this time. I sent a response to their support and am waiting back on a response.

I am well over their recommended amount of caster. I ordered extra fluid so I can pull the box and bench test it.

@mudmaster - I'm glad you have a PSC box and have not had any of these issues. That gives me hope that maybe I can get my steering back to where it was a week ago.

 

[afusco1222]

Update: After speaking with support at PSC, they sent me a new box. I received it the next day being that I live in Austin and PSC is outside of Fort Worth. When I opened the box today, i found that the red lines didn't line up like the old box did when I received it. Does anyone think this will be a problem or should I line up both lines and run with it?

BTW, orange tag says the lines should line up when you install it. It says nothing about moving the splined shaft to match the housing.

 

[mudmaster]

Update: After speaking with support at PSC, they sent me a new box. I received it the next day being that I live in Austin and PSC is outside of Fort Worth. When I opened the box today, i found that the red lines didn't line up like the old box did when I received it. Does anyone think this will be a problem or should I line up both lines and run with it?
View attachment 578588

BTW, orange tag says the lines should line up when you install it. It says nothing about moving the splined shaft to match the housing.

Line them up and install. When lined up the shaft should be in the center of travel

 

[afusco1222]

I got the second box installed and now I have a new problem. The dead spot in the middle of the steering wheel is huge. It makes it very difficult to change lanes and S turns can get a little dicey. I have verified that everything is tight under the Jeep, even the steering shaft. I've attached a video, and I realize that it wasn't the smartest way to take the video but it was the best way to show that the Jeep tracks straight even with the wheel turned from 11 - 2 position. Is this normal for PSC to have his amount of play in it?

 

[NashvilleTJ]

I got the second box installed and now I have a new problem. The dead spot in the middle of the steering wheel is huge. It makes it very difficult to change lanes and S turns can get a little dicey. I have verified that everything is tight under the Jeep, even the steering shaft. I've attached a video, and I realize that it wasn't the smartest way to take the video but it was the best way to show that the Jeep tracks straight even with the wheel turned from 11 - 2 position. Is this normal for PSC to have his amount of play in it?

That very likely has nothing to do with the PSC setup - assuming it is installed correctly. You have a steering issue somewhere unrelated to the PSC. Have you done a dry steer test?

The PSC ram only sees pressure when there is significant resistance to turning the tires. At all other times - including driving down the highway - it provides zero assist. If you disconnect the drag link from the pitman arm and try to turn, nothing happens because there is no resistance. Now if you go full lock, the steering gear sees resistance, and only then the ram will move. That is the difference between and assist setup like you have, and full hydro.

 

[mudmaster]

I got the second box installed and now I have a new problem. The dead spot in the middle of the steering wheel is huge. It makes it very difficult to change lanes and S turns can get a little dicey. I have verified that everything is tight under the Jeep, even the steering shaft. I've attached a video, and I realize that it wasn't the smartest way to take the video but it was the best way to show that the Jeep tracks straight even with the wheel turned from 11 - 2 position. Is this normal for PSC to have his amount of play in it?

It's not normal. Mine has no issues.