Help with '03 ZF Steering Box to Saginaw Conversion!

[chef_vader]

My 2003 TJ SE with the 2.4L motor and Mercedes ZF steering gear has had a leaking steering gear input seal for months. I finally found this post http://www.rubiconownersforum.com/f...1757-steering-box-input-seal-replacement.html that walks one through the rebuild.

My rebuild failed. I think one of the loose ball bearings in the ZF style box got loose in the housing, made a terrible grinding noise after I bled the lines and started her up. It's scary, and also undrivable. I do not want to drop $500 on a rebuilt ZF box. So I have a few questions about going to a Saginaw box.

1. Can I use the stock power steering pump that I already have?
2. Will I need new lines? I just bought brand new high pressure and return lines for the re-installation ZF box setup.
3. Will the steering shaft from the steering wheel fit the splines on the Saginaw box, or does that need to be replaced also?
4. The ZF Setup used ATF4 instead of power steering fluid. Is that a function of the pump, or the gear box? What fluid would I use assuming I reuse my pump with the Saginaw box?

I know that's a lot, but I just don't want another mistake to keep me from enjoying my Jeep! Thanks!

 

[Jerry Bransford]

@mrblaine is a member here who is a guru on steering systems (among everything else on our Jeeps) so hopefully he'll see this and answer your questions.

 

[chef_vader]

Thanks for the bump Jerry. Hopefully he see it. What a nightmare I made for myself!

 

[StG58]

That does sound like a MrBlaine set of questions.

 

[Chris]

This is totally a @mrblaine question. Last time I picked his brain about steering setups he blew my mind with his knowledge.

 

[mrblaine]

My 2003 TJ SE with the 2.4L motor and Mercedes ZF steering gear has had a leaking steering gear input seal for months. I finally found this post http://www.rubiconownersforum.com/f...1757-steering-box-input-seal-replacement.html that walks one through the rebuild.

My rebuild failed. I think one of the loose ball bearings in the ZF style box got loose in the housing, made a terrible grinding noise after I bled the lines and started her up. It's scary, and also undrivable. I do not want to drop $500 on a rebuilt ZF box. So I have a few questions about going to a Saginaw box.

1. Can I use the stock power steering pump that I already have?

Yes, the pump will work with the reservoir it has.

2. Will I need new lines? I just bought brand new high pressure and return lines for the re-installation ZF box setup.

Yes, you will need the lines for the 97-02 Saginaw steering gear.

3. Will the steering shaft from the steering wheel fit the splines on the Saginaw box, or does that need to be replaced also?

Yes the shaft will fit the splines. What will be difficult if you do not have a body lift is making the lower shaft from the carrier bearing to the steering gear work. The short shaft that fits onto the input shaft of the steering gear is two different lengths. The 03-06 is longer so it sticks up higher when used with the Saginaw box. Without a body lift, it can rub on the bottom of the overflow for the coolant. The easy solution is to acquire the lower steering shaft from a 97-02 and swap it in.

4. The ZF Setup used ATF4 instead of power steering fluid. Is that a function of the pump, or the gear box? What fluid would I use assuming I reuse my pump with the Saginaw box?

I know that's a lot, but I just don't want another mistake to keep me from enjoying my Jeep! Thanks!

Use the ATF+4 that the pump likes. The box won't care.

All that said, are you sure the grinding noise is in the gear and not the pump? The pump makes a grindy sounding noise when it isn't bled correctly. You may have an air lock in the gear that won't let the pump bleed fully. Make sure first before you do the swap.


The question I didn't see was if the Saginaw box would bolt up and it won't. You will need to cut the forward bolt sleeve loose in the frame and relocate it.

 

[chef_vader]

Wow! Thanks @mrblaine for the detailed response. I am aware of the frame modification. The grinding from the pump is interesting, but either way I need to go ahead and replace the gear. The seal I replaced is leaking worse than before so I clearly screwed that portion up.

If I were to go ahead with the saginaw box swap, would I need lines for a 2.5 or 4.0 motor? My 2.4 has the sensor port on the high pressure line, and from what I can tell the 2.5 has it as well, but not the 4.0 line.

In regards to the steering shaft, would I be okay to drill the plastic pin out and adjust the length, or do I absolutely need to get a new lower shaft?

 

[mrblaine]

Wow! Thanks @mrblaine for the detailed response. I am aware of the frame modification. The grinding from the pump is interesting, but either way I need to go ahead and replace the gear. The seal I replaced is leaking worse than before so I clearly screwed that portion up.

If I were to go ahead with the saginaw box swap, would I need lines for a 2.5 or 4.0 motor? My 2.4 has the sensor port on the high pressure line, and from what I can tell the 2.5 has it as well, but not the 4.0 line.

In regards to the steering shaft, would I be okay to drill the plastic pin out and adjust the length, or do I absolutely need to get a new lower shaft?

The sensor port is for the idle up feature on the 4 cylinders. When the pressure increases in the system from too much force needed to turn the tires at idle, the sensor in the line tells the PCM to kick up the idle so it won't stall the motor. That means you will need the lines from a 4 cylinder from a rig that originally had the Saginaw gear due to how they are bent and where they are located on the steering gear. You will not be able to re-bend your current lines to fit unless you are a lot better at it than anyone I know.

The plastic pin isn't what you think it is. It is only in the outer shell of the collapsible portion and is only about 1/8" deep and it's function is likely the injection port for the plastic they squirt in there to lock the shaft in place until it needs to collapse in a frontal collision. The shim is what provides the friction to hold the two shafts together and stop them from moving around separately from each other and developing slop. The pin does not extend from the outer shell to the inner shaft to lock it in place. But, you can drill it to release some tension and try to shorten it enough to work. As I stated, you may run into interference with the bottom of the overflow reservoir if you don't have a body lift.

 

[Mykii]

I love this so much. @mrblaine seems to be such a wealth of knowledge! GAAAH, I really wish there were more knowledgable people that are willing to share such intricate details for swaps like this. I had a 2.5 TJ and now have a 4.0 TJ. Ended up here while looking for Saginaw replacements, but came through this thread for the read. Not sure who is active still here, but I'm looking forward to creeping this forum and getting all the info I can to make my TJ a bit better-- then providing info to others who may need it as well.