I dismantled the idler box and I would like to know what is the proper fill procedure for the ldler box and the proper fill level for the steering box . Also is 90w marine oil ok or 80w 90 better choice for the idler.For the steering box lm Guessing that the 80w 90 EP oil is recommended .

1. The idler box oil level doesn't have be exact. Basically, you want the lower body well (where the vanes are) to be filled, and you want the top area between the middle plate and the top cover to be mostly air. Reason being, the oil is forced through those little ball hearing check valves in the middle plate and that provides some of the dampening action. You don't want the idler to be 100% full because then the oil can't move around and it might lock up if the steering is moving quickly.

2. Yes, the steering box requires EP oil, as does the differential. All other oils can be regular. 80 to 90 weight oil in the idler should be fine, and some people experiment with other viscosities to get a different feel. Everything from motor oil to grease. I'd stick with the 80 to 90 weight oil. Heavier oils tend to leak less from the bottom seal but also have a slightly stiffer steering response.

3. 80, 85, or 90 weight EP oil should be fine for the steering box. Or a multigrade like 80W-90 or 85W-90. It won't make a lot of difference, but do use EP.

-Bryan

Thank you for that great detailed Explanation. Exactly what I needed to know.

What is EP and where can you find it ?

tima01864 wrote:What is EP and where can you find it ?

EP = Extreme Pressure, and any store with an automotive section will likely have it. EP oils are also known by the designations GL-4 and GL-5, and the oil has additives such as sulfur compounds that give it additional lubrication protection for gears in high contact pressure usage. For our Fiats, that would be the worm and roller gear of the steering box and the ring and pinion gear of the differential.

The sulfur compounds are also what gives EP oils that nasty smell. Some specialty EP oils use chlorine and phosphorous compounds, but sulfur is the most common. It's also why you can't use EP oils with "yellow metals" such as brass/bronze, so you shouldn't use EP oil in the Fiat transmission as the synchros are brass and will corrode with EP oils. EP oils also attack copper, by the way. I've heard of folks using GL-4 in Fiat transmissions, which might be OK for a while as GL-4 has less sulfur additives than GL-5 does. I'm still not recommending it.

More than you wanted to know perhaps, but there you have it.

-Bryan

Thanks Bryan.