I know this subject has been discussed somewhat. So I have this low growling sound coming from the rear end I guess, not really sure. I crawled under it and checked the u joints which seem fine. Jacked up the wheels and both are tight, no movement. The rear end oil is still amber and at the right level. Obviuosl;y something causing the sound. I really don't want to tear into the axles/rearend without some further assurance from some more asute Areostar owners as to exactly what might be the issue. It is a 7.5 rearend and the van has 77,000 miles on it. Any suggestions, hopefully a pin point diagnosis.

 

run at freeway speeds for 20 miles +, then pull off road into safe place and immediately test for hot spots on u joints, pinion and rear axle housing

signs of a bearing failing are often a leaking seal
look closely around the front pinion seal and pull rear drums and look for leaks on back plate below axle shaft seal
all it may be is a seep

loose parts on exhaust or on rear suspension can cause harmonic noises at road speeds

does the noise change with veh. speed? up-down hill?
engine load or gear?

have someone set in back seat and listen out side windows when noisy present to pinpoint side...then have them lay on floor over rear end and listen to pinpoint noise

 

I'll try the 20 miles on the highway tommorrow and check for hot spots that is a good suggestion.


The pinion seal is not leaking, however I will cjeck the axle seals.

I have a new exhaust and the noise was the same as with the old.

It does increae in volume up to a certain level and pretty much stays at that level I think above 20 mph. It decreases in volume when I let off the gas. Thats why I think it is in the rear end.

 

I had this same problem - and it was how the one bend in the exhaust was vibrating on the axle - you really have to watch how you rebolt the tail pipe to the muffler, since it can get a bit tight there when you lower the van... but I know you say you just re-did the exhaust - still - I found that the cause was because the springs/shocks were older and starting to ride the van lower, thus not allowing the right clearance... Does it only happen at certian speed ranges? that was my thing... drove me nuts... but I think you might have a different problem, since mine wasn't until I hit the higher speeds...

 

I didn't feel any hot spots in the key areas. I am getting ready to take it out w/the wife and listen for the noise location. The noise was the same prior to me changing out the muffler and tail pipe. I am thinking it may be the third member gears/ring and pinion but it is just odd as there is only 77,000 miles on it. It has howled since I bought it with 74000 miles and have driven it out on the highway 4 times at about 100 miles each and it hasn't changed a bit. I would think if it was a bearing the noise would have increased somewhat after the 3-4oo0 miles. But I just don't know.

 

bearings can stay the way they are for a while or fail all at once - I've seen both...

I just replaced my wifes front wheel bearing today on her chevy - and it has been bad for 2 years, but it never got any worse, never made any sounds, etc - but I got tired of having to worry about it... I have a friend that goes through wheel bearings really fast (ford pick up) - but he abuses the truck... would be a great commercial for "ford tough"

in anycase, have you tried something silly like lifting the rear end, and rotating the wheels by hand? unless you never hear it until 20MPH... also, does it sound worse or the same when you take corners?

 

Well crapola, I guess I didn't check the wheel good yesterday. I pulled the wheel and drum off and I think maybe the sound was from the brake shoes dragging for some reason. The drum was tight pulling it ogg


SO, what I did find is there is in and out play in the pass side axle. Maybe close to an 1/8 in movement. Seems loose to me but not sure why.

 

Hi - I have this exact same thing on my 89 - love to find out why there is play on mine as well - the one side is tight, but the other isn't - I'm not getting your sound though :-) My play is more like a 1/16th - an 1/8th is more than I have, but it's the same situation - I was going to ask about this actually, but forgot about it til now :-) Is this how the rear wheel bearings start to show wear? Not quite sure here....

 

that's about the correct end play on Aero rear axle....C clip lock on inner end allows for some in/out play

the important test is turning the axle hub by hand and testing for smoothness and examining around seal for seeps and leaks

with drums installed and rear brakes adjusted, there should be no sound of dragginb shoes in rear drums

causes
weak return springs
rusted corroded old cylinder pistons and bores
hanging parking brake shoe
brake flex line breaking down internally, not letting break fluid to return

 

hi 96,

so, if both ends turn ok with no binding, etc, and no leaks, we are good there? Do rear wheel bearings wear out before they start to leak the Diff fluid from the Rearend? I know you have seen your fair share of them :-)

 

leaking hypoid grease is an indication the bearing is worn out and loose

BUT, bearings can be noisy from galling and pitting of rollers and/or axle shaft race, usually caused by water in rear end bearings from deep water hole or cheap quality bearings...and with no grease leak out seal

problem with Aero and most Ford axles is that the axle steel is the inner race that the bearing rollers ride on.....

aftermarket does make an offset bearing that rides on different part of axle as inner race

if there is more than 100k on rear end especially if rear end hypoid grease is not changed every 50k and you have ruled out other causes of noise, I would go thru the rear end
jack up on jack stands, pop diff cover off and drain out old grease
pull C clips and pull axles out, careful of seal
examine bearing and shaft for wear and galling
do same for front pinion shaft bearing mindful of bearing preload on nut

also examine ring/pinion gears for proper tooth engagement and wear...examine spider gears and shafts for wear and looseness

I usually just order new axle shaft bearings, new front pinion bearing, seals and replace all while i have it torn down for exam
they do wear out

new 75w90 hypoid grease only....Valvoline makes a quality synthetic that is reasonably priced

will run more than a day on vacation if one goes out 1000 miles from home

 

There are no seal leakage anywhere. Maybe the end play was closer to 1/16th of an inch, but I thought that was odd to have any play there at all. So I took it into the shop today and I'll wait and see what they say. There has to be something causing the noise. Although I suspected it to be the brake shoe dragging it may not be the cause. Sure sounded like it and the drum was a little tighter than what I have experinced in the past from other vehicles.

 

Does your rear end have the limited slip differential? If so, excessive end play of the axle shafts indicate very worn clutches. If not, there should not be anymore than about 1/16" play, as others mentioned.

The low growl sounds to me like a rear bearing starting to go. It happened to one of my previous cars, and there were no oil leakage anywhere in the rear end. The noise grew to a low rumbling, until finally it ended up with actual grinding noises. In my case, the bearing disintegrated to the point that the bearing seals were getting chewed up by the loose *****.

I worked on this other car that had a front wheel bearing that did pretty much the same thing; growl, rumble, grind. The bearing generated so much heat that it welded itself to the spindle, and we had to replace it. I think that was caused by the driver hitting a curb at some point in the past.

 

I had the mechanic look at the gears today. He said the oil was clean, the bearing looked good and the spider gears are worn. He siad he could replace them but couldn't guarentee that would elimate the noise. Next step he said could be to replace everything. I need to take a trip this weekend so I asked him if it is to the point of needing to be replced and he said no. Just keep on driving it if you can stand the noise. So I think I will drive it until I can get to the salvage yard and see what I can find or just have the gears replced. He had no idea why they were worn.

 

as long as the diff oil was clean of any metal cuttings, i would not worry....the spiders could not be worn that much or there would be indication in oil and bottom of housing....

the spiders only work on turns...rig must have been used alot in intown hvy delivery?

did he check the pinion bearings front and rear?
did he take u joints apart and check for dry bearing?