I have a 96 B250. I don't drive it a lot, but in the summertime when temps here in Phoenix get a little toasty and I'm driving on the freeway, I start to get this weird noise, kinda like a deep groan. The noise starts and stops, and it seems like the van loses a little of power. But when the temps cool down at nite, it runs perfectly. It also runs great when I'm just running errands around town on surface streets.

Any ideas?

 

When I had my '94 B250, awhile ago, when I would drive it on the freeway, (it was summer as I recall) with steady pressure on the gas, I would hear a steady slight noise, like I was driving on the rumble strip on the side of the freeway lane. Not that the noise was loud, as it was a subtle noise, but the tempo of the noise was like driving on that grooved strip. The noise would go away as soon as I left off the gas, but would return within seconds after re-applying a steady gas foot pressure again. It never happened around town, or maybe I just could not hear it.

I described the noise to a transmission mechanic that I had used the previous year to do maintenance on the tranny. He nodded his head and added a small bottle of additive into the transmission, something like 4-6 ounces as I recall. He then told me to drive the van around and see if I could get it to do it again. The transmission never made that sound again. He never charged me for the additive, and I never knew exactly what it was. As I recall he said the clutches in the tranny were chattering and the additive fixed that condition.

 

Interesting. Did it lose power or struggle to change gears?

 

It only seemed to do it while on the freeway, steady freeway speeds, so I was not asking it to change gears, although dropping out of overdrive, or going back manually did not affect the noise once it started. Only thing I could do to stop the noise was to let off on the gas pedal, but it picked back up once I stepped on the gas and attained a steady speed again. Again, the noise was not loud, and could be drown out by the radio easily. I had passengers, and they could hear it too. This noise was a very rhythmic noise, upping in tempo as the van went faster, but I did not notice it doing something like 40 or 50 MPH. I described it to the mechanic as like I was driving on the freeway edge, along those vibration grooves they put on the freeways to wake you up if you are drifting off the edge, but not nearly that loud.

This was not my daily driver at the time, and I would use the van to go camping or visiting usually a long distance. I had had the tranny rebuilt, and I think I might have had maybe 50-60,000 on this unit when the problem cropped up. I wrecked the van when the rebuilt tranny had about 130,000 on it, and it was working good at that time. Hope this helps.

 

You know often, a bearing on the drive shaft will growl like you describe. Have you crawled under the van and tried to twist the driveshaft by hand to see if the bearings on each end are loose? How about a bad front wheel bearing? Have you jacked up the front end and tried to move the tires by hand looking for a loose wheel bearing? If you try to spin the wheel by hand, you should be able to determine if the bearing is bad also, as you should be able to spin the wheel easily and it should continue to spin at least a couple of revolutions with no noise at all.

 

I’ve got this same problem and when I turn my driveshaft in neutral w the wheels on the ground , it turns a lil bit.

however when I spin the back drivers wheel I hear some scrapping which I now know is a bad wheelbering? That and the loud howling I get at 30 mph+. But when n I let off the gas it stops, starts as soon as I step back on the gas. Is that consistent with a wheel bearing ? Or more trans? Or driveshaft bearing?

I always assumed it was my differential, so I redid that, no difference.

 

I suspect that would be more likely to be the pinion bearing. Axle bearings are always under load, so, they should howl whether you are on the gas or not. Pinion bearings, on the other hand, are only loaded when you are applying power.... (which includes steady state driving.)

 

I had a similar situation and it was my ring gear

 

Ah thank you, so I was in the right direction with the differential? I’m sorry I don’t know terminology so well. That’s the end of the driveshaft where it connects to the rear diff, right?

 

Driveshaft connects to the pinion gear, pinion gear drives the ring gear. If they wear funny, they get loud. If a bearing is marginal, it can allow them to be out of alignment, and carnage ensues. Howling is just the first step. Wouldn't hurt to pull the cover, and have a look.... of course, it likely won't be patently obvious.