[Chief]

OP, I'd guess some conflict in the ring gear/pinion area...don't you drive a V10 Dodge? They have had read end trouble with both the 1/2 ton and the 3/4 ton trucks, even though the 3/4 is supposed to have the bigger Dana rear end...put the truck on jack stands ( rear half), block the front wheels just in case and have someone put it in drive and run it up to 60...stand back towards the rear of the truck...have them let off the gas, have a listen and see if you can duplicate the noise.

[HotRodTodd]

Chief is corect, your backlash on your pinion is most likely the cause. Do you tow a heavy trailer? That is usually the cause of the coast wear in the rear. A few years ago dana changed the way they assemble their pinions. They used to be shimmed with no crush collar on the pinion bearing. Since 97 i believe they have started using a crush collar now and then torquing the pinion nut to achieve the proper depth in the housing. Your truck is probably a 2500 with the dana 60, at least those are the ones ive seen this on the most lately. The Ford 250s also tear them up too, same center section. If you determine that this is your problem it can be fixed if you havent let it go to long. Find a shop that specializes in performance work and have them elimnate the crush collar and just use shims when they reset the pinion depth and change the bearings and seals of course. It can be done with the right shims so it wont give you anymore problems for years and years. Good Luck

[HotRodTodd]

Originally Posted by oldphart

the front is a Dana 60, the rear is a Spicer 70, the truck is a 98 with 120k and it had a receiver hitch on it with elect brakes when I bought it so I'm assuming it's carried it's share of loads..although it was a fleet vehicle from some video rental outfit that went titties. The growl is ever so slight and about all I drive nowdays is from home to the marina, about 20 miles a day.

Damn thats strange. Is this a single or dual rear wheel truck? I have a 96 3500 dually and it has 780,000 miles but every one i have seen has the dana/spicer 80 series. My old 82 D-450 has the 70 series with 350,000 miles, its been bullet proof so far and it weighs 12,500 lbs with the boom and onan in the utility body. I dont think that they changed the 70s, unless its a single wheel type, most of the trucks i see are duallys or the 2500s with the 60series rears. I havent seen a 70 or 80 have any problems except for the ocasional broken yoke from extreme abuse. Have you checked your carier bearing? Usually when the rubber is cracked or really soft it will start to give you some vibration, i havent heard the growl symptom but it is possible i guess. If your truck does have single rear wheels, it should be the 60 rear and 120,000 is about the right mileage when the problems have been showing up. Let me know some more details and i will try to help.