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I'm stumped. 2001 E250 van will produce howl sound when letting off gas at 40 MPH. Doesn't do it at any other speed. I bit the bullet and installed brand new differential gears and bearings - made no difference.. noise is still there at the same speed! How could that be? Must not be differential noise?
Any guesses what might be making this noise?
Worn parts somewhere in the transmission? Torque converter?
How about backlash? It's set perfectly right at 0.008. More? Less? Too late to change it anyway?
Different weight oil? Heavier? Lighter? Dana says 90, Ford says 140.
Yes, drive at 40, shift to neutral, foot off gas - no noise.
Thing that is confusing is this has the symptoms of a ring and pinion issue, but after both those were changed out for brand new gears, it still does the same thing. One would think that with new gears, something would change. That's why I wonder if it's something other than the gears. But what?
Not certain if you can duplicate the issue while the car is on the rack [rear end lifted], but that is what I would try to do.
Problems like this are always frustrating because people assume what they did or that the new parts they used are good. Never assume you did the job right or the parts you used are any good.
The 40 mph seems like it would not be the differential because it either makes noise under load/no load or does not. Do you know if the transmission is on 3rd gear or OD? Try turning OD off.
Also, have someone else drive and crawl around the van to locate the source. The box can mask the source of a noise to someone in the drivers seat.
Last edited by Don Ridley; Feb 5, 2026 at 09:20 AM.
Not certain if you can duplicate the issue while the car is on the rack [rear end lifted], but that is what I would try to do.
Problems like this are always frustrating because people assume what they did or that the new parts they used are good. Never assume you did the job right or the parts you used are any good.
Yes, understood, but wouldn't think it would do exactly the same thing - would think at least something would change. But nothing did. That's why I'm asking about other possibilities.
The 40 mph seems like it would not be the differential because it either makes noise under load/no load or does not. Do you know if the transmission is on 3rd gear or OD? Try turning OD off.
Also, have someone else drive and crawl around the van to locate the source. The box can mask the source of a noise to someone in the drivers seat.
would think at least something would change. But nothing did.
Been there too often when I was a kid, learning my trade. I remember a service manager once asked me while I was a Shop Foreman, Why do we not have enough time to do it right the first time, but we always find the time on the second/third attempt?
Hind sight is 20/20 and assuming can get you in trouble. I agree, I would think that the differential was the root cause but now I would attempt to spend a couple minutes to prove I was on the right track or not. It would take two people and there is a bit of an issue with spinning tires/driveshafts hitting flesh. When I was a kid, I would have just shoved one in and then freak out on what to tell the service advisor.
Using a hose and putting one end up to your ear and the other end where you think the noise is coming from keeps your head out of those moving items. A long pry bar/screw driver also works too but they are not as flexible as a rubber hose.
As someone mentioned, noise at specific speeds may not be the differential.
Well I had the drive shaft disconnected of course, but didn't look at the U-joints. What would I look for? Would the joints indicate wear if moved by hand?
If you could remove the driveshaft, check the motion of the U joint on each end. The joints should rotate smoothly and freely in each of their axes. Each axis has the two bearings that allows the "flex" motion between the driveshaft and transmission or differential. Any amount of stiffness in the motions indicate that the bearings are probably worn.
Also, there should be no play along the rotation of the driveshaft; tangent to each of the axes. The test is done with the transmission in neutral, and grab the driveshaft to see if you can twist it and see play between it and the differential. Unfortunately, this is the easy test that may not reveal problems. The joints could be jammed and still not show any play.
I've seen binding U-Joints and they tend to cause vibration problems but it's just too easy not to check them and replace them if they are binding/loose.
Time and money well spent while you are trying to resolve this issue. You don't want to have the driveshaft come loose once the howling is resolved and maybe the howling is caused by the U-Joint.
I did a visual and a "tug" on the U-joints. They feel completely solid - no odd or loose movement.
Just got back from a 3000 mile trip. New gear set and bearings in place. Still howling around 40 MPH. Sigh. I'm thinking about opening it back up and increasing the backlash. I can't think of anything else to try. Any other suggestions appreciated.
Here is the pattern after 3000 miles. Yup, there is a pretty hard line down toward the root. But the contact patch is nicely centered. (The small black dot on one tooth is just a spot of grease). Rechecked backlash - right at .009, perfect according to the book.
The old set I removed looked very similar - a harder line on the root end, so am thinking that may be OK.
What to do here? Try loosening the backlash? Try installing the old gear set? Buy another new ring and pinion and start over?
Last edited by N147JK; May 16, 2026 at 12:40 PM.
Reason: pictures
Yes, drive at 40, shift to neutral, foot off gas - no noise.
Thing that is confusing is this has the symptoms of a ring and pinion issue, but after both those were changed out for brand new gears, it still does the same thing. One would think that with new gears, something would change. That's why I wonder if it's something other than the gears. But what?
The transmission is the only moving part that changes it's configuration with speed. You have carefully inspected the differential, u joints etc. But the transmission and all it's moving parts has not been interrogated. I don't know how to troubleshoot transmission problems. Maybe pay a local shop for an evaluation. I would do this before spending more money on the differential. If it makes you feel better...I heard whining noises on my E350 and assumed it was the tranny with 200k miles. After paying for a rebuild, it turned out to be spun bearings in the differential.
