Hi All,
I have a 99 4.0 that suffers from the dreaded power steering whine/moan. At idle, I've gotten it pretty quiet with a Seafoam Trans Tune flush and fresh fluid, ( ) and removed all the air. But when turning, (even lifted and no resistance), i get the same noise as this guy:

Reading the comments, one guy mentioned a Ford Bulletin that calls for an inline filter. Maybe my Google skills are lacking, but I can't find anything on the interwebs from Ford. But I did stumble across this post:
Power Steering Filter

Is this really a solution? I'm not against replacing the pump, but there's countless stories of the same whine coming back. I'm all about a more permanent solution, but I'm fearful the filter would decrease return flow. And does anyone know the inner diameter of the return hose? Not just for a filter option, but I'd like to do another flush, (3rd one now?) without making a huge mess and want to add some aquarium tubing or whatever off the cooler return port.

I've read everything from adding Lucas Stop Leak to a cap full of brake fluid to adding Motorcraft friction addictive. Does anyone know if there's a real solution out there? I know it's a "Ford thing" but I can't imagine someone driving this truck new off the lot had this issue.

Oh, and this generation originally called for MERCON Multi-Purpose (ATF) Transmission Fluid XT-2-QDX. I know Mercon ATF has been superseded by Mercon V, but is that XT-2-QDX the same and able to be swapped with Mercon V?

 

Let me be the one to tell you that I put mercon V in my 1993 ranger and it has been just fine. It wasn't as loud as yours is but it got a bit quieter. And that's my suggestion for you. Change your fluid. You can do it the full way by unhooking the lines under the truck and draining, but there are some precautions to this, you dont want air in the lines. Or you can do what I did, which is the turkey baster method. Suck out the reservoir with a baster, refill with fresh mercon V. Drive around for a couple days. REpeat the cycle as many times as necessary to get the fluid to look like fresh cherry red MErcon V. I think I did it 5 or 6 times. Obviously this doesn't get 100% of the old fluid out, but if you do it like I did you'll have a majority of new fluid in there and it will be better. The only other fix to your issue is a new pump. I personally wouldnt mess with filters. Too much work for too little gain, and it may not even work.

 

Thanks Stackz! That video isn't my truck, but it's still a great comparison. To be honest, I'm getting a little encouraged. I've "flushed" it like 3 times now. Each time, I've unhooked the return line off the cooler at the bottom, turned the wheels countless times, and poured fresh ATF, (I think Mercon V the first time and then Valvoline full synthetic the other two). After the first flush and later the second, the fluid immediately turned dark again. I mean immediately. This third flush definitely tinted the fluid, but it's more of a apple red now, (instead of what I'd call cherry red). The sound at idle with no pressure on the steering is great. But any load when turning brings back that whine.

I don't mind flushing it a million more times, but I'd love to unhook the return line off the reservoir and put some hosing over that and run it out of the truck. Then pour fresh Mercon V and keep adding until what runs out is a nice red. The only problem I'm having is what size rubber cap I'd need to seal off the return port on the reservoir. Finding that type of information on the internet seems to be getting harder these days or something.

 

please dont mix different types of ATF. Only mercon V in that power steering system. Dont get the orielly brand stuff even though it says "mercon v compatible" or whatever. Spend the extra cash, get the real deal on ebay. I paid 60 bucks for a 5qt jug, should be enough for what youre doing. You need to drain out that valvoline, you just made more work for yourself.

 

The only permanent fix is to do the Saginaw TC swap (Proquipped bracket) or P-series swap (Cardone #206244 pump). Ford pumps will always whine.

https://proquipped.com/shop/ols/products/p1-adapter-kit

https://www.therangerstation.com/Mag...naw_pump.shtml