Full hydro issues - JeepForum.com
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post #1 of 12 Old 03-08-2020, 04:16 PM Thread Starter
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Full hydro issues

So I've installed a full hydro system in my jeep. For the most part, everything seems to be working properly and the system appears to be fully bled (no more milk shake in the reservoir). The biggest issue I'm having right now is the system feels normal while stopped but when I'm moving, the steering wheel feels so light that it's tough to drive straight on the road without bracing my arm against something. I've got just under 3 turns of the wheel from lock to lock so it's faster than original but not by a lot. The other issue I'm having is the steering wheel doesn't have a constant center even though I have a double ended PSC ram.

I'm sitting at about 9 degrees of caster, 3/16" of toe in, and 38" tires.

Any ideas?



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post #2 of 12 Old 03-08-2020, 04:36 PM
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You using this as a DD street jeep? FH set ups tend to be a hand full on the street.

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post #3 of 12 Old 03-08-2020, 04:37 PM
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I'm not an expert by far, but I'm pretty sure this is why fully hydraulic steering is illegal in some states. Why would it return to center? As your RPM and pump speed increase, the effort to turn the tires is going to decrease.

This all sounds normal to me.

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post #4 of 12 Old 03-08-2020, 04:47 PM
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Not sure about legality what i looked real quick, Tennessee and would include New Jersey since you can not do any welding to the track bar etc, mounts must be stock bla bla.. But if the motor dies going down the road, you are SOL.

short street usage to a trail is all everyone i know does and at slow speeds anyway. Or its on a trailer.

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post #5 of 12 Old 03-08-2020, 06:15 PM Thread Starter
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Wonder if I could underdrive the pump without compromising offroad strength... I don't regularly drive this on the road but I do like to occasionally.

A lot of the myths regarding full hydro are orbital dependent. This one is load reactive meaning it will return to center and almost all of them have a check valve that allows for steering with the engine off. In fact, you're supposed to steer the wheels off the ground and the engine off to bleed it initially anyway. I think a lot of people claim full hydro can't be used with the engine off because they tried it with low tire pressure in the rocks and didn't have the nuts to turn the steering wheel. For my jeep, it's actually easier to turn full hydro with the engine off than it was with my old stock gearbox.

edit to address legality: The only state that I know of that makes full hydro illegal is Tennessee. Tennessee technically also makes all steering mods illegal including hi-steer, hydro assist, one ton steering, etc because the law states "It is unlawful to modify a vehicle's original steering system..." By New Jersey's laws, even a load reactive full hydro setup is fully legal because it will return to center.
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post #6 of 12 Old 03-09-2020, 03:42 AM
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I was going to say more caster, but you said you are running 9 degrees. I am running 7 degrees and its fine on the road (at least it was fine to the 55 mph I have taken it so far). Try messing with your toe some more. Maybe try toe out? I feel like I read that somewhere when someone was having issues with full hydro. What size ram and what size orbital are you running? Also what size are your feed and returns?

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post #7 of 12 Old 03-09-2020, 07:32 AM Thread Starter
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Quote:
Originally Posted by 87TPIYJ View Post
I was going to say more caster, but you said you are running 9 degrees. I am running 7 degrees and its fine on the road (at least it was fine to the 55 mph I have taken it so far). Try messing with your toe some more. Maybe try toe out? I feel like I read that somewhere when someone was having issues with full hydro. What size ram and what size orbital are you running? Also what size are your feed and returns?
I was going to try different toe settings next. I have heard of people with big tires having more success with toe out but have never experimented with it.

The ram is a PSC 2.5 Inch Bore X 8 Inch Stroke X 1.50 Inch Rod Diameter and the orbital is a 160cc. All of my lines are 1/4" -6AN including the initial return from the orbital but then I step it up to 5/16" before the cooler and keep that diameter back to the pump. I probably should run a -8AN from the orbital to the cooler but just haven't gotten there yet. There have been a lot of other more pressing issues and the lines don't leak so that got put on the back burner.


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post #8 of 12 Old 03-09-2020, 07:49 AM Thread Starter
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Was thinking about this in my other car this morning and I think part of the problem is the hydraulic steering has no dead zone. In most cars, there is a tiny amount of play in the steering wheel which we've instinctively learned to push through and this Jeep had a large amount of play before this so turning the wheel 1/8 of a turn for anything was fairly normal and that's a pretty big input now.


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post #9 of 12 Old 03-09-2020, 07:50 AM
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Quote:
Originally Posted by Waternut View Post
I was going to try different toe settings next. I have heard of people with big tires having more success with toe out but have never experimented with it.



The ram is a PSC 2.5 Inch Bore X 8 Inch Stroke X 1.50 Inch Rod Diameter and the orbital is a 160cc. All of my lines are 1/4" -6AN including the initial return from the orbital but then I step it up to 5/16" before the cooler and keep that diameter back to the pump. I probably should run a -8AN from the orbital to the cooler but just haven't gotten there yet. There have been a lot of other more pressing issues and the lines don't leak so that got put on the back burner.


It could be the orbital to ram ratio. I have the 120cc orbital with the same ram. Also running -8AN return with a -12AN feed from the resi.

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post #10 of 12 Old 03-09-2020, 08:38 AM Thread Starter
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Originally Posted by 87TPIYJ View Post
It could be the orbital to ram ratio. I have the 120cc orbital with the same ram. Also running -8AN return with a -12AN feed from the resi.
I actually wanted to use a 120cc orbital. However, the source I used could get me a 100cc or a 160cc orbital for $250 with a 2 year warranty and I wasn't willing to pay twice the price with half the warranty for an Eaton 120 especially considering so many people run a 160 with this ram anyway. In hindsight, the 100 probably would've been the better option but I didn't like the slow steering rate that my jeep had before so I figured speeding it up a little would make it more normal compared to all my other vehicles. I didn't consider the steering would feel like an old 70's steering wheel with a super light feel.

I may put the stock Jeep steering wheel back on since it's a larger diameter than what I'm currently running. I've also considered wrapping the steering shaft with rubber or something to put a small amount of drag on the steering column itself to make the feel a little more tight. Sounds like I've got some tinkering to do.


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post #11 of 12 Old 03-09-2020, 08:52 AM
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Could also got to a larger ram.

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post #12 of 12 Old 03-09-2020, 07:24 PM Thread Starter
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Ok so I added some extra toe in and changed from a smaller diameter steering wheel back to the larger stock size steering wheel. Both of those made a huge difference in drive-ability. However, past 55-60mph, I was noticing I still had some wander. Started looking a little deeper and noticed that one of my top ball joint nuts was loose despite the cotter pin still being in place. I gave that ball joint 3/4 of a turn and that helped a little more but it's still got a small wander above 60mph. At this point, I'm kinda thinking the big cut bias ply tires are likely the culprit now and the stock steering was just masking the issues between the occasional episodes of death wobble.


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