ZF Suspension-RL-85/E and RL85/A Steerable Tag Diagram/Steering Gearbox 8098

ZF Suspension-RL-85/E and RL85/A Steerable Tag Diagram/Steering Gearbox 8098 - Printable Version

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RE: ZF Suspension-RL-85/E and RL85/A Steerable Tag Diagram/Steering Gearbox 8098 - jdkskyking - 09-07-2023

Mine is the early version. I’d imagine yours has the shocks with feedback or even lowers at highway speed? I’m not familiar with the evolution.

I would imagine the ZF RAS is similar, you probably have 365 on the tag. Not sure how that changes things but the principle is the same. I believe I have uploaded the documents that explain how it works. I know there is a ZF 7.5 ton system and a 9 ton version.

The nuts and bolts of my situation, I lost the nitrogen pressure in the accumulator, that allows the rear of the coach to sway back and forth because the rear CENTERING CYLINDER needs the pressure to hold the tags straight going down the road. Crack the whip with my Gladiator in tow. I am of the opinion that I drove it that way long enough to shorten the life expectancy of the bushings. I had a tag bushing that was comprised. This week I found a drive bushing in a similar state. They’re keeping a lot of weight in check back there.

This entire experience was more “discovery” than anything as I was apparently the first to bring this to the attention of the Newell Service Department. The manager told me about the service life, annual inspection/servicing, adding the accumulator to the PMI, and that they now stock the accumulator.

My anal retentive tendency and high expectations is why I decided to essentially zero time the suspension. Newell and I replaced almost every single component of the ZF Rear Axle Steering System because we were understanding ever we were dealing with. I contacted a German company with extensive ZF RAS experience and was given valuable information. I’m not done yet.

You should have a pressure sensor on the tag accumulator system that will alert you to a low pressure situation. My sensor was also inoperative. How unusual.

Besides my coach driving like crap, the true first symptom was while backing up, the tags turned in the wrong direction.

If EVERYTHING is setup properly, good system. If not, potential problems.

I just read a FB post about rubber smell in the tow vehicle. I had the same. Thought it was my Jeep tires. It was the drive tires going in one direction and the tags going in another. Scrubbing. Ruined a new set of tags on a trip because of it.
It as a problem “synchronizing” the the two hydraulic cylinders in the system AND the all wheel alignment. The new service manager Dusty got the alignment rack in order with a new third party tech to ensure the rack is calibrated properly. Mine was completely out of tolerances for various reasons.

Two more drive axle control arms and the rear is done. I’ll get to the steers when I figure out a way to change the bearings without completely removing the steer A arms.

Like I said, then the icing on the cake but I’ll document that after I’ve accomplished it and validated the reason for it.

JK

RE: ZF Suspension-RL-85/E and RL85/A Steerable Tag Diagram/Steering Gearbox 8098 - jdkskyking - 04-01-2024

Newell just finished replacing all eight airbags with new ZF airbags.

When Newell removed the drive tires they found a cracked rotor and brake pads destroyed.

My advice is to pay to have the tires removed and visually inspect and measure rotor and pad thickness.

I requested that an alignment be completed since I replaced all eight control arm/bushings for the drive and tag axles.

During the process the tag axle hydraulic pressure was check. Gauge indicated 150 psi. 100 psi low! I DID NOT HAVE A TAG AXLE INDICATOR AT THE DRIVER POSITION.
The pressure sensor had also failed. That’s two failed sensors on my coach since I’ve owned it. In theory, when the pressure in the ZF RAS drops below 230 psi, a warning light should illuminate at the driver annunciator panel.

We noticed two of the hydraulic lines that connect the REAR CENTERING CYLINDER to the rear ZF RAS HYDRAULIC BLOCK were wet. We replaced all four lines with a high quality line. Cost was $150 at a local Miami OK shop Newell uses.

Newell has decided to increase the ZF RAS hydraulic pressure to 275 psi.
I’m in the process of determine what the accumulator nitrogen charge should be set to.

As a reminder, I was told that the ZF RAS pressure accumulator has a 10 year lifespan and the system pressures should be checked annually.

I certainly hope to continue to increase my knowledge on the ZF suspension system and work to keep owners informed.

JK

RE: ZF Suspension-RL-85/E and RL85/A Steerable Tag Diagram/Steering Gearbox 8098 - RobSC - 04-01-2024

Nice write-up on the ZF suspension. These things are a different animal for sure.

RE: ZF Suspension-RL-85/E and RL85/A Steerable Tag Diagram/Steering Gearbox 8098 - hypoxia - 04-16-2024

I see the nitrogen pressure should be 10 bar, 145 PSI and hydraulic pressure should be 15 bar, 217 PSI according to page 11 of the attached ZF Servocom RAS manual. Is this the wrong manual?

ZF Rear Axle Steering.pdf Size: 1.12 MB Downloads: 15

RE: ZF Suspension-RL-85/E and RL85/A Steerable Tag Diagram/Steering Gearbox 8098 - jdkskyking - 04-16-2024

There are disclaimers in the document that reference the manufacturer specifications.

At this time, I’m unsure why Newell has increased to 275 psi.

As far as documentation, they are difficult to find. Newell does not offer published specifications.

JK

RE: ZF Suspension-RL-85/E and RL85/A Steerable Tag Diagram/Steering Gearbox 8098 - CaptainGizmo - 04-18-2024

Such great info, Jeff…thanks for taking the time to detail it.

You’ll be happy to know that Newell has now stepped up their game in terms of servicing and replacing the accumulator. I had mine replaced a couple months ago.

Just heard, today, they’ve built a portable charging rig they can take down to Indio each year.

RE: ZF Suspension-RL-85/E and RL85/A Steerable Tag Diagram/Steering Gearbox 8098 - jdkskyking - 04-18-2024

It is very important to have the ZF RAS (Rear Axle Steering) hydraulic system inspected and serviced. Make sure to keep an eye on your four hydraulic lines connected to the Rear Centering Cylinder. I replaced all four of mine when I picked up the coach from service work recently. The four hydraulic lines are exposed to road debris and the elements. The hydraulic lines that were replaced were wet and collected debris.

HYDAC makes a pressure gauge that attaches directly to the nitrogen valve on the bottle. I’m trying to find out more information about the gauge unit.

The accumulator is pre-charged to approximately 150 psi with nitrogen. The hydraulic side of the system is then pressurized to between 250 and 275 psi.
If your system is weeping fluid like mine apparently did, the system pressure will decrease.

In 2021 I had a complete accumulator and hydraulic pressure failure. The coach could not be backed up because the system pressure holds the TAG axle straight as we backup until the steering axle system moves beyond 5° of center. In my experience, the TAG tires will move in one direction or the other based on forces of the road surface. Mine moved in the same direction as the steer tires and the coach stopped moving.

And to answer your next question… you can drive forward because of the TAG Axle Caster but it will likely handle poorly as the TAG Tires can move slightly left or right.

Accumulator Data I recorded from a new unit.

Manufacturer:
HYDAC 66280
Made in Germany

(Part Numbers)
02112867/663/010
BOSCH 3591.005.099

Pre-Charge of 10 BAR (145 psi)

V 2L

PS 40 BAR
PT 143 BAR

TS-40/80° C

As usual information about the accumulator is difficult to find. If anyone can decode the above information please post.

Keep an eye on your TAG Tire sidewalls for unusual scrubbing which could be a symptom of low ZF RAS hydraulic pressure.

More to come…
JK

RE: ZF Suspension-RL-85/E and RL85/A Steerable Tag Diagram/Steering Gearbox 8098 - hypoxia - 04-19-2024

Your Bosch number crosses to quite a few manufacturers; MCI 11-07-1000, MB A 000 430 17 02, MB 000 430 17 02, TAT 336529120, FIO 336529120000, HAB 662957, VOL 3987649, FIO 3311104, RVI 58 10 115 414, MAN 82 47301 6010, GRS 82473016010, MB 82250002430, ENA 3311104, SIU 1793010081, PAI 2200360000, VSO 44123000350 and the Hydac 02112867/663/010 is available from Find it Parts Accumulator

Any information on the pressure sensor switch?

RE: ZF Suspension-RL-85/E and RL85/A Steerable Tag Diagram/Steering Gearbox 8098 - jdkskyking - 04-19-2024

I too found it on “Find it Parts” and ordered one last night. I’ll be interested to see if it’s the real deal.

As far as the system pressure sensor… I find it odd I’ve had two back to back failures of the sensor that doesn’t warn me up front.

I have pics of the sensor. I’ll try to find it.

JK

RE: ZF Suspension-RL-85/E and RL85/A Steerable Tag Diagram/Steering Gearbox 8098 - jdkskyking - 04-19-2024