Dave D(SK)

I have an odd noise that started several years ago and neither my dealer or I have been able to solve. Maybe someone out there in diesel truck land can help.

I have noticed this at other speeds but it is predominate just after truck shifts into overdrive at about 50 mph. It sounds somewhat like a bad tire noise (an undulating sound) but I can’t pinpoint its source. It can be annoyingly loud at times but disappears at about 55 mph. It is also worse when I am towing or have a heavy load in the box. To avoid this noise I often lockout overdrive until speed is over 55 then engage overdrive.

Since this noise has started, for one reason or another I have had the following repairs/maintenance. Replaced all tires, replaced all ball joints, modified exhaust system, rebuilt transmission, inspected drive shaft and u-joints. I am beginning to think the problem may be in the engine which would disappoint me since the engine was still under warranty when problem started. Since this has been occurring for almost 100K miles, it doesn’t seem to be harming anything but if could get rid of it, I would spend some money restoring truck and keep on driving it rather than spend the big bucks for a new one.

Thanks for any suggestions.

96, 2WD auto, 250,000 kms (Canada)

b.lee

there is no "shuddering" going on?
How does it shift otherwise?
what kind of noise is it, I dont know what 'undulating' is.

Dave D(SK)

There is no shuddering, shifting is normal, can't say I notice any vibration, other than the noise, truck seems to operate normally.

undulating - Sorry about this choice of words but it is hard to describe a sound in a text forum. By undulatng I mean the sound increases and decreases in level. The closest thing I can use to describe it is I have heard tire noise that sounds similar. But I have gone through a couple of sets of tires since it started and sound never changed plus I have heard it while driving on gravel and have never heard tire noise on gravel.

I've been living with this for a long time and other than being annoying it hasn't effected truck otherwise but now that I am considering selling to buy another it will definetely effect the resale or trade in value. If I was buying a used vehicle and it made this noise I surely wouldn't buy it.

96_12V

Undulating - is it possibly a bearing (like the rear output shaft bearing on the transmission) or a U-joint on the driveshaft? If not those, I would be looking into the rear differential...good luck with this one.

Unfortunetly, odd noises, rattles, creaks, etc. are what often doom a vechile long before major component wear-out. It just gets to the point we can't take it anymore! I sold a '95 Volvo 850 turbo after only a year of ownership and with only 75k miles on it, as nearly everything squeaked, rattled, moaned, or buzzed. To be fair, the car had been in Chicago for it's first 65,000 miles of life and had been pounded on those hard, unforgiving streets. I didn't take issue with it, I simply sent it on it's merry way.

Earthmover627

mine made a simular noise at the same speeds and it was the overdrive pump was out, it made that noise for three years before the tranny finally gave out.

Dave D(SK)

96 12V, thanks for the comments, I have checked all components except rear end, may have to look into it.

Earthmover627, I'll check with the shop that rebuilt my transmission and see what they have to say.

Thanks

v8440

I'd check hanger bearing on driveshaft first, then pinion bearings in rear axle. If it turns out to be one or more of the pinion bearings, I'd like to see a picture or two of the race from the offending bearings-that might teach us something to look for.

infidel

Check that the motor and tranny mounting bolts are tight.
Check the flex plate bolts also.