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Tech Question
neil schroll, Mount Joy, PA, 1969 Dodge Charger 440
I have a high pitched hummm/whirr eminating from my 8&3/4, 742 case differential at about 100 mph +. When you drop back below this speed, it goes away. How do I fix this problem with out always driving slower than 100 mph???
The rear was recently set-up & rebuilt with all new bearings, new clutches for the posi, new axle bearings, and a good used set of 3.23 gears. I also have a new drive shaft from Denny's drive shafts. The transmission is the 727.
I appreciate any help/advice you can give me on this matter.
Oh, and by the way, great magazine! I received my first subscription this past December, and I love it. Keep up the great tech work.
Thanks.
Neil-
There's really ony two places that rear axle noise can come from: the bearings, and the gears. Typically, bearing noise is a whine or growl that increases proportionally in frequency and volume with road speed. Gear whine, however, can vary with road speed in an almost random way, and can occur under drive, coast, or both conditions.
Setting up used gears is a touchy situation. Once they are broken it is sometimes impossible to re-install them and have them be silent -- and sometimes not! I suggest dropping out the carrier and having a good, close look at the gear contact pattern. Try re-setting it to get it as close to the book -- or the original wear pattern -- as possible.
If this doesn't help, as long as the gear contact area isn't bottoming out, or running off the edge of a tooth, the life expectancy should still be decent. (Check the temperature of the carrier, and the lube, after a top-end run, just to be sure all is well. I'd be unhappy with anything over about 220 deg. Farenheit). If OK...you may just need louder mufflers and/or a radio! (Or, of course, another gearset).
Rick
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