I have a 2000 3500 diesel. I just got off of the phone with my wife and she says that there is fluid coming out of the rear differential, where the drive shaft connects to the differential. I suspect the front seal of the differential is blown. I have a couple of questions that I hope you can help me with:

1) How much and what type of oil does the rear diff take?
2) This isn't something I'm going to be able to get to right away. It may be up to a week before I can take a look at it and possibly fix it. If she keeps the diff oil full, will she be able to make short trips with the truck?
3) Is this something a novice mechanic can fix?
4) If is is something a novice can fix, what special tools, if any, will I need?
5) If this is something I should not attempt myself, how much should I expect to pay a professional for this fix?

Thank you for your time and I appreciate any answers given. If more information is needed, I'll provide it to the best of my ability.

 

leaking from the front of the differential, where the drive shaft bolts up - is a leaking pinion seal. fairly common problem. not overly hard to replace, except requires air wrench. not overly expensive.

1. GL5 gear oil. 85w90 is fine. 75W140 is also fine but very expensive. friction modifier needed if you have an LSD, your 3500 diff is large, so about 2.5-3 quarts,
2, yes. there is a fill plug on the rear cover. just cut the spout, tilt it up, and shove it in the hole. fill until it runs out. replace plug. as long as you keep it full, you can run on as long as you want. the leak is probably slow, although a slow leak will make a heck of a mess and look bad.
3,4. its slightly above beginner level. requires impact wrench to remove pinion nut. requires a little experience and/or inch pound wrench to do it right. any good shop can do it. there are several good do-it-yourselfs on the internet. i recently taught myself how to do it on son-in-laws leaky jeep. we did front and rear. due to crappy timken seal, we got to do the rear twice. you must have impact. also the right way is to check rotational resistance with 1/4 inch beam style torque wrench.
5. most shops can do this pretty quick. i read of $100-150 in labor from some. other shops did a complete disassembly for a boatload of money. be sure and a use good seal, either National from Advance, SKF from Napa, or oem. anything but timken.


this is how you measure the rotational torque.
an experienced mechanic can do it by feel.
http://www.amazon.com/Park-Tool-TW-1.../dp/B000NVCI1U

 

Can slightly over size seal be use or is one even available??

 

They don't make oversized seals, however, they DO make 'sleeves' to put over the yoke if the area the seal rides on is damaged. (need to take if off to see if you need it...) Or, you can just get the 'stock' seal, and replace the yoke. Getting the sleeve to go on there right is an exercise, and very easy to screw up.

 

no to oversize seal. not needed. just replace it with $10 National.
very unlikely you would need a sleeve or new yoke unless you've got 2 million miles on it.

the most important thing is to keep your differential full between now and the repair, whenever that might be. i drove the old chevy once for several months with a badly leaking seal. it would leave a small puddle every night, and i'd refill it about once a week with a cupful or less.

 

Also consider that pinion seal leaks can often be caused by a bad pinion bearing..

 

Thanks for all the replies.

I wish I were mechanical enough to do the repair on my own but, I'm fairly certain I'm going to have to pay someone else to do the job.

 

bad pinion bearing will talk to you and let you know of its bad condition.
it yell something like this at you all the time - ROAR ROAR ROAR ROAR.
LOL.

keep it topped off, call a couple of shops and get prices.
also find out if you have an LSD or not, as it needs an oil additive which will add a few more dollars.

 

How do I find out if I have a Limited Slip Differential (LSD)?

It took me a bit to figure out what 'LSD' meant :)

 

look on your sticker, either in glove box or under hood. look for words like "open"=non-LSD or "anti-spin"=LSD.

and/or look on rear axle tube, drivers side for the remnants of a part number sticker. it'll have your gear ratio and diff type. something like 3.55 Open or 4.10 Anti-Spin.

haha, it doesn't mean acid.