Cracked Front Differential

[ewoksammich]

Hi everyone. I've been lurking for quite some time now. Started on the "Site that shall not be named", migrated to the Nation, and now here. My problem is this: I have a 2002 Trailblazer EXT. My wife was using it to get to and from work this past winter and, without my knowing, was using the A4WD function as opposed to the 4HI or 4LO. One morning I found a massive trail of what appeared to be oil running down my driveway under the truck. I looked and searched, and I'm 99% sure that the reason for the trail of oil was the 6 inch vertical crack in my front differential case. My wife said she heard a grinding noise when she was driving, then heard a pop and thought she blew a tire. She looked and everything seemed fine, so she drove 25 miles back home. My question is this: Is there a way to remove just the front "half" of the case to inspect the carrier assembly? If the spider gears and carrier are fine and nothing is sheared or cracked off, can I just have the case welded along the crack? I really want to avoid the ten hours of labor that would go into replacing the entire differential. Also, to answer any questions No. The differential fluids were not changed or checked at regular intervals. I didn't buy the vehicle until after it hit the 150K mile mark. I had the trans fluid flushed and changed, and oil changes were regularly performed by me. I've searched and read, but I haven't seen anyone simply "fix" their differential. Everyone seems to replace it. I appreciate any help anyone can offer. Thanks!

[The Roadie]

Welcome, and sorry for the problems. I also have never heard of welding it in place. You don't want to strand your wife on the road with a failed repair, so you might consider just deleting the front driveshaft and CV shafts and downgrading to 2WD.

That said, I'd be terrified that the transfer case is beyond toast and that could take out even your 2WD function. Differentials are a 100K sort of item, but the transfer case needs fluid every 50K for a good reason.

[ewoksammich]

I had a feeling you'd be the first to respond Roadie. I'm honestly hoping that the problem just lies in the cracked differential and nowhere else. I've looked in the service manual, and it looks like the only way to remove the cover would be to remove the entire assembly. Am I correct in assuming that? Thank you for the quick response!

[Eredin]

I had a feeling you'd be the first to respond Roadie. I'm honestly hoping that the problem just lies in the cracked differential and nowhere else. I've looked in the service manual, and it looks like the only way to remove the cover would be to remove the entire assembly. Am I correct in assuming that? Thank you for the quick response!

You would be correct, the bolts that hold the halves together are facing the oil pan and cannot be removed without dropping the diff. I do have a write up on the diff removal, as I suffered through that recently. I do have an EFAN, so you'd need to add additional steps to remove your fan shroud and mechanical fan. Sadly, the A4WD is too abrasive and destroys the diff, as you've seen.

[ewoksammich]

I did read through your technique Eredin, mainly because I'm SERIOUSLY trying to avoid dropping that oil pan. I suppose I was looking for an easy way out, when there isn't one. I just don't want to suffer from the flashbacks that everyone who removes theirs has.

[ErikSS]

I can understand your desire to avoid pulling the differential. However, the chances of a case breaking without something else going on is very slim. You likely have damage inside. Roadies idea to pull the CV shafts (I suggest the prop shaft or front drive shaft as well) would buy you time while you look at options and gather parts.

[ewoksammich]

Very good point. She didn't hit anything, so I'm assuming it was the use of the A4WD that did it. Probably easiest to just replace the differential while I have it off as opposed to putting a band-aid on it. Thanks everyone for the help!

[v7guy]

I'm with the other guys, you could weld it, but the odds of it not moving around and throwing things outta spec are pretty small. It'll likely warp and nothing will fit. Best bet would definitely be to just replace it.

It's a pretty odd failure, especially considering it still had oil in it.

[ewoksammich]

Yeah it's looking like I'll have to suck it up and replace it. That's what I though too. It wasn't like "Aww man. Look at this little streak of oil...". I literally thought the oil pan was broken, or I lost the drain plug because there was so much. Oh well. As an aside, does anyone think that since I'll be changing out the diff, that this would be a good time to switch up to a 4.10 if I can even find one?

[TBYODA]

You might as well since your going though all that trouble, I would. And as I understand taking the front diff out the engine bay is the easiest. Were you located maybe there someone near by that could help.

[Anthony Hernandez]

Ide weld it..

[ErikSS]

Ide weld it..

Ide lolololololol Maybe he means "I'd"

[Eredin]

Highly recommend the 4.10 upgrade, even on stock tires. Car-Part.com is your friend. I found my front diff and had it shipped flat rate from Ohio, so I didn't have to go fetch it. The rear, on the other hand, I drove two hours to get. Since you have an 02, any year will work, but 02-05 are usually cheaper because of the lack of ABS sensors. Remember to source an 8.6 rear, price difference is usually worth it.

[escapepilot]

You might as well since your going though all that trouble, I would. And as I understand taking the front diff out the engine bay is the easiest. Were you located maybe there someone near by that could help.

I've read the threads on removing the diff this way also. Question - is it still easier to go through the engine compartment if its a 5.3?

[ewoksammich]

Thanks for the advice Eredin. I'm actually located in Northwest Indiana. About 35 minutes from ErikSS actually. I think I'm gonna move up to the 4.10, since I already planned on the upgrade further down the road. Might as well do it after the headache of removing it. I've found one or two on Ebay, but the price is insane.

[Shdwdrgn]

It's possible to take the diff out through the bottom without removing the oil pan (you have to drop the steering linkage and jack up the motor a little). You might get lucky and find the magic hole right off, or like me you might spend hours twisting and turning before it finally falls out... but once you find that point it seems to slide in and out like butter after that. Oh, and spend a little extra to replace all three seals before you put the new one in, because the last thing you want to do is lose another weekend pulling it again for a $10 part.

And yeah, for the effort involved you might as well switch to the 4.10s. Unless you spend 100% of your driving in the interstate, the 3.42's are good for nothing except making GM's numbers look better. Most of my driving is spent in rush-hour traffic, and the 4.10's respond a lot better, and haven't affected my mileage. Once you make it through the front diff, swapping out the rear will be a breeze. It's a rather expensive upgrade, but its oh-so worth it.

[Eredin]

Jeff is right, don't skip the seals. Don't cheap out on them either, getting them direct from the stealership is worth it in this case, as most of the aftermarket seals have been known to fail quickly. You'll need all three of them, I believe the part numbers are in my thread IIRC.

[navigator]

If he changes the pinion seal, doesn't that back pressure off the crush sleeve? Would he have to change the crush sleeve? I thought the guy that did my rear said the crush sleeve was a one time use type of part. I don't begin to know how to set up the gears but I remember him tightening up the pinion nut carefully and using a beam style torque wrench to get something like 17 in lbs of torque on the pinion nutnut forward and backward. Seems ,like used bearings need a few less lbs if I remember correctly.

[v7guy]

Some guys have reused crush sleeves, they're suppose to be a one time use item.
Pinion bearing preload is measured in inch lbs and the resistance is lower with used bearings. I had to order a new torque wrench to get one that read low enough to do the job.

[Eredin]

Sorry, I meant the disconnect seal, since it must be pulled too. I ended up leaving my pinion seal on mine and replaced the other two.