Engine/Transmission (1994 - 1998) Do I need to change pinion seal

[GMichaels]

have a 97 3500 and would like to change diff oil to synthetic. I notice that the pinion seal has a very minor leak, no drips but you can see an oil stain as is slowly leaks.



my understanding is synthetic will leak where other non syth oils won't.



Should I plan on changing the seal, and can this be done without removing the pinion?

 

[kentdiesel]

If it’s just weeping and not dripping I would run it and take a look at the diff about once a week to see if it’s getting worst. My pinion seal leaked with dino oil at 86,000 mi so I think they could start leaking anytime no matter what oil you run. I replaced the seal and went with Mobil 1 synthetic gear oil and its been dry ever since. You don’t have to remove the pinion to replace the seal. If you decide to replace the seal this is generally what you need to do.



Remove the rear cover to drain diff, unbolt the drive shaft at the pinion yoke, remove pinion yoke nut and washer, remove pinion yoke, remove seal, replace in reverse order, fill with oil.



You will need a good impact wrench to remove and tighten the nut. I used a 3/4" drive impact wrench because I didn't have a socket big enough in 1/2" drive. A 1/2"impact wrench may remove it, I don't know.



The pinion yoke can be extremely hard to pull off. The Manual shows a plate style puller which would be easy to make. I used a huge 2 jaw puller and I had to tighten it far beyond what thought it would take to remove the yoke. It would be good if you had a Seal Driver large enough to cover the entire seal so you could drive it in straight and not peck round and round with a hammer. Sand the yoke where the seal rides with some 600 grit sand paper to polish it alittle. I reused the old nut and washer. You can mark the end of the pinion and the nut to give a reference of where to tighten . I made a combo Seal Driver in the Lathe that works for the axle seals and the pinion seal.

The pinion seal I bought was about $12. 00 cheaper at NAPA than the local Dodge dealer who didn't have it in stock.

 

[GAmes]

I had my seal replaced because of a slight leak at about 300k. Over the miles the seal had worn a groove in the pinion yoke, requireing it to be changed as well. If you are high mileage you need to have both.

 

[PToombs]

Before you get too excited, check the diff vent to make sure it is open. They do plug up, and the resulting pressure will cause a leak.

 

[Advantage Take]

where is the diff vent located?? I have replaced the seal 3 times in the last month. leaks really bad. huge spots in the driveway and both of my trailers are covered in diff lube. though about a speedy sleeve but I see no grooves, pits or burrs on the yoke, pinion, or housing.

 

[Joseph Donnelly]

Most of the differentials used in our Turbo Diesels have a collapsible spacer (“crush sleeve” between the two pinion bearings, not a solid spacer or shim. You must be careful not to overtighten the pinion nut on re-installation or bearing preload will be excessive. First brush and spray clean the area of the pinion nut and companion flange. Measure the depth from the end of the pinion stem to the nut with vernier calipers. Put a paint mark from the center of the pinion stem outwards across the nut and onto the flange. Then, remove the pinion nut by holding the flange with a piece of bar stock or angle iron that you make up to bolt to two of the positions on the flange, and a ¾” drive socket and breaker bar with “cheater” pipe to turn the nut. Pull the flange and replace the seal, putting a good grease on the lips of the seal and the surface of the flange it rides on. Replace the flange and nut with blue loctite on the threads. Carefully tighten the nut so the paint marks line up and then just a little bit more, and check with the calipers to be sure you aren't one thread away from being tight. It is common for the tapered roller bearings to take a “set” and you think the nut is tight when it really is a thread off from being tight. If you can turn the flange some while tightening the nut, that will help keep the rollers aligned.



If you are experiencing any leakage at all with conventional lube, the leak will probably get a lot worse with synthetic lube. The manufacturer has to use additives to help keep the seals soft and swollen with synthetics, and the additives often don't work as well as the natural ingredients of a petroleum-based lube like the excellent Lubrication Engineers #607. I use that lube in all my differentials, including the high-friction 9” Ford type, which exhibits gear scuffing with many other lubes in heavy service. Mag Hytec can sell you that lube, if you decide on it. If you have another preferred source for lubricants, see what they have that helps keep seals from leaking while providing superior lubrication and scuff resistance.