Put my 2000 Dodge 2500 5 spd in shop to have pinion seal replaced. Bought repl.fluid, Castrol Syntec. Picked it up and on the way home, noticed a whine in diff. when using motor to slow down (trans downshift) Took it back to shop and was told preload on gearset was 0. They put it back like it was. After some calling around ( to diff specialist) was told my gear set had either spun the bearing race in the pinion, or the rear end was worn out. At 92 K miles? Any suggestions or opinions appreciated.

 

seems to me they over torqued the pinion nut and had no backlash. the wineing noise is the pinion to deep in the ring gear. i would bring it back and make the garage fix it could get $$$ depends on wut has failed.

 

before i spent the money on a new rear end, i'd replace the crush sleeve on the pinion and reset the preload. the shop replacing your seal may have under/over tightened.

 

Pinion depth is set by shims. Torqueing the nut does not affect the pinion depth as long as its zero-clearance or preloaded.

Also, preload is set by shims as well. No crush collar in the d80.

Looking at the service manual, only applicable causes for whine that I see is low lube or loose pinion bearings (not enough preload). If the latter were the case, it could cause the pinion to move deeper into the housing and change pinion depth/backlash. Torque on the nut is between 440-500 lb.-ft., so you might want to get a big wrench. 1-7/8", I believe. Double checking fluid level would be the easiest thing.

 

Thank you all for your input. The truck is back in the shop that changed the seal. It is scheduled for tear down next week. I have all new bearings and races, new seal,etc. Will post results, good or bad, when resolved.

O. G. Randle Texas

 

You might want to pay a visit to that shop and be sure that they can properly set up gears. The only way that you would have had a 0 proload is if the pinion and or the differential bearings are ng. There should be some preload even with the miles you have on it. The difference will be weather your gears last for a couple of 100k or 20k.

 

I plan to be there when the tear down and reassembly takes place. How do I tell if the mech. knows what the hell he is doing? i.e.--What do I look for in the set-up?
O. G. Randle

 

Just thought I'd point out that you said Castrol Syn-Tec instead of Castrol Syn-Torq.

Syn-Tec is motor oil, but you knew that already.........right?

...........Jim

 

Sorry, mispoke myself. I didn't try to use Syntec motor oil in the diff. It was gear lube. (Castrol) ----O. G. Randle

 

The gears are designed to mesh at a specific point on the teeth for full strength and no noise. The preload is to keep the tooth mesh correct for full strength. Your differential parts will flex under load so if you get a good contact pattern without any preload when you put alot of torque on it the contact area will walk up the tooth and the contact pattern will degrade. The wear on the gear goes up and the strength goes down. To check the shop ask to see the contact pattern on the set up gears. At that time also ask them what value they got for the preload. If you are not sure about them make them show you before they put the cover back on. Setting up gears takes time and is sort of a art form. Alot of shops that are not specialists in setup will give it a shot and if the pattern looks close enough to not howl out the door it goes. By the time it fails or starts to make noise they can make all sorts of reasonable excuses for why it failed. If your truck started making noise right after it left the shop I would not trust them unless I could see the installed gear set in the rig and have them show me the installation. Good Luck

 

Truck is home, fixed, no charge for 2nd trip. Pinion nut not tight enough. In adequate air supply for impact wrench. Had to call in a mobile tire repair truck w/ 1" drive impact wrench. 500ft/lbs + loctite solved the prob. Pinion does not have crush sleeve. Thanks everyone. --O. G. Randle