PSC and RPM upgrade - Now steering is too sensitive over 50 MPH

lloydrage

lloydrage

Member
Guys,

Good morning. I need some input here. I recently upgraded my steering set up on my 2017 JKUR to PSC hydro assist with cylinder and I added the RPM 2.5 ton drag link and tie rod set up at the same time. I did the self alignment (done this for years so not first time) and I am having an issue. Once the jeep gets to 45/50 mph it feels way too sensitive. The slightest adjustment makes it dart too far to one side and then when I try to correct it, it overcorrects and same thing.

Its not death wobble or anything, its just very sensitive.

I checked and everything appears to be torqued correctly and aligned. My caster is 7° and my toe-in is about 1/16". Any idea on what I could be missing?

thanks

Lloyd
 
cozdude said:
Higher caster like you have will cause the steering to feel more sensitive, especially with the new hydro being so strong compared to stock. If you bring your caster back down closer to factory spec of 4.2* it should help
Click to expand...
PSC says, "To achieve the best on-the-road driveability, recommended front axle caster setting is 7 degrees POSITIVE."

www.pscmotorsports.com

PSC Cylinder Assist™ Steering Kit for 2012-18 Jeep Wrangler JK 3.6L with OE Axle

PSC has developed the BIG BORE XD Steering Kits to be the ultimate steering upgrade package for Jeep JK/JKUs equipped with locking differentials, aftermarket axles, and up to 44" tire sizes. All kits include our top of the line components including the BIG BORE XD Steering Gear...
www.pscmotorsports.com www.pscmotorsports.com
 
Hydro assist steering in general is going to be sensitive and can feel twitchy; might just need to get used to it and adapt driving style to suit.

You could also try switching to a smaller ram; I'm guessing you likely have a 1.75", could try a 1.5".
 
What kbp810 said, hydro assist will make your steering feel very sensitive. It takes some getting used to but it is totally normal.
 
Lloyd, did you ever get this figured out?

I am actually having a similar problem... I had the PSC full hydro kit on my stock Dana 44, when I switched to the ProRock 60s this past winter, I also upgraded the Ram to the longer 8" vs the 6" I had (also larger diameter). Previously it drove great (dana 44s). Now I am okay below 50 mph but it gets a bit squirrely above that. Feels like it is to fast off center at speed.

I've had two shops align the jeep... it is where it should be otherwise. Before I took it to a 4x4 shop I spent several weeks trying to dial it in myself... which has never been a problem and I installed the first kit on this jeep in my garage... when I took it in for an alignment I was told nothing needed to be changed, it was "perfect".

This one has me beat. I know the Dynatrac axles have added positive caster to begin with (about 2 degrees positive over factory). I've moved it every way possible... I can drive it, off road it is fantastic. On the highway it sorta scares the crap out of me.

Any solution you found would be appreciated.

Oh, and PSC told me to go get it aligned... wish I would have thought of that.

~Lost
 
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Either you have something loose, or your alignment is wrong. 😄

Unless something is moving by itself, the Jeep should drive straight, given proper alignment and tire pressures.
 
cozdude said:
Higher caster like you have will cause the steering to feel more sensitive, especially with the new hydro being so strong compared to stock. If you bring your caster back down closer to factory spec of 4.2* it should help
Click to expand...
At speed, positive camber keeps the tires going straight and forces them to return straight after a turn. This makes steering LESS sensitive and more stable.
 
Disciple Off Road said:
You mean Hydro assist? Or you actually mean FULL Hydro? But yes positive castor is your friend with PSC.
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Thank you for the clarification... what I intended to say was the complete Hydro assist kit. I did not ever plan for this vehicle to be off road only.

I never said it didn't drive straight... I said at speeds over 50 it is quick to turn off center. Nothing is loose, tire pressures are subjective and should be adjusted based on the driving conditions, and I've adjusted the caster everywhere between +2.5 to +8 degrees. That said, those are the first things I checked and then paid two different shops to check as well.

This particular jeep has a stock 3.6 and 5.38 gears... 115 MPH is not an option.

~Lost
 
I’m guessing here but 5:38’s im assuming at 50 the rpm’s are high on 37’s ? with the PSC pulley designed for more output at lower rpm . Could be higher pressures quicker reaction at speed ?
 
JT@623 said:
I’m guessing here but 5:38’s im assuming at 50 the rpm’s are high on 37’s ? with the PSC pulley designed for more output at lower rpm . Could be higher pressures quicker reaction at speed ?
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That is my guess as well. The jeep is running around 2200-2500 rpm @ 50 mph. It will run 70-75 mph @ around 3500 rpm (I will need to do a better job of monitoring the rpm at that speed). I have enough room to run 40's, just didn't want to at least not yet.
 
Pump speed pressures could be factors. If the pressure relief flows are restricted you could be seeing higher pressure which would make the cylinder react faster.

for example if max flow is 20gpm at 2200 rpm, max pressure is 1500 psi relief/return is 1400 psi which equals around 3gpm.
if the pump is spinning at 2500 rpm and 25gpm your return would need to handle the extra 2 gpm if restricted pressure could be 1450psi.
 
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