I have a noise I'm trying to diagnose on my 93 Aerostar AWD. The noise is totally linear to speed, not affected by gear/engine rpm, only vehicle speed (still there when gliding with engine off). You can't hear noises coming from any wheel. It's more of a low rumble (no vibration though) than a howl which is why I'm confused (all other toasted rear-ends I've driven "howl"). It starts at a very low speed but doesn't really get super loud (my wife didn't notice it). I've checked u-joints (removed drive shaft), they're okay. From inside the vehicle, it doesn't really sound like it's coming from the rear diff but what else could make this noise? It does have AWD and sounds like it could be from the back part of the transfer case but when you open the engine access cover under the dash, you can't really hear it better. I put it on jackstands on the back and spun the wheels, seems okay except a bit of clicking noise from differential (seemed like a normal noise, couldn't really tell).
The van has 95K miles. It's a standard diff, not a traction control. About two weeks before the noise my wife was backing up and it felt like brake was on (it wasn't). After a bit of gas something "popped" loose with a snap. I'm thinking this is part of the problem (bearing, broken tooth?).

Should I remove the rear cover from the diff and inspect? Can you see if the gears are scored or am I just looking for chips, chunks or shavings? Can I safely put the vehicle up on jack stands and run it in gear and see where the noise is coming from? Anything else it could be?

Thanks very much,
Mark Biederbeck

 

[font size="1" color="#FF0000"]LAST EDITED ON 10-Jul-01 AT 04:29 PM (EST)[/font][p]My 91 E4WD had similar noises as you describe. Mine turned out to be a loose pinion nut and a worn differential cross shaft. I rebuilt the rear end along with new rear wheel bearings and everything is nice and quiet now. That popping noise while backing up could be from the front CV joints/transfer case binding up - Aerostars are notorious for this. At 95K miles, your differential should be in good shape. If you do have a clicking sound back there it may indeed be a bearing or gear. Turning by hand, you should hear a steady "whirr". If the click occurs at the same place each revolution, you may need to pull the cover and check it out.

 

Hey thanks,

I was digging through the archives and saw your posting, was going to contact you but you beat me to it. Did you do this work yourself? Would you consider it striaghtforward as long as you're not messing with the ring/pinion or is that unavoidable? Would you mind telling me what you paid for parts/labor?

Many thanks!
Mark