Diesel Place banner

1 - 9 of 9 Posts

·
Registered
Joined
·
22 Posts
Discussion Starter #1
Hey y'all,

After doing some wrenching this morning I discovered that I have what I assume to be a front diff leak.

I inspected the floor before starting and it was totally dry. After changing out some pulleys and serpentine belts, starting the engine about 5 times for short periods of time, I discovered that the floor was not so dry anymore...

637367


The oil was not totally clear - it had a hint of red or brown. I suspect this is ATF coming from the front diff.


637368


I'm guessing just changing out a U-bolt won't fix it.

637369


So I again turn to the "elders" and the knowledgeable of this forum. Am I off in my assumption that this is a front diff leak? Could there be a rotten O-ring that's causing this?

I recently changed engine oil, and haven't put many miles on it after. I still think the engine oil would be significantly darker/blacker that what I discovered on the floor today.

At the same time, I think it's been years since the front diff oil has been changed, wouldn't that also be darker/blacker and not almost totally clear?
 

·
Registered
1995 GMC Suburban
Joined
·
17,908 Posts
Can you smell the fluid? I know it is gross.
From smell you can narrow down, we know it is not diesel.

Trans fluid and GM Coolant are red.
Not sure if the red is just in the picture or is it really red stain.
Worn out trans fluid can be brown and it smell like trans fluid (compare with trans fluid dipstick).

The Gear Oil in differential smell really strong sulfur but not red.

There is also Power Steering above all these part that can leak.
Depends on what you use, sometimes it is P/S fluid, sometimes Trans fluid used in P/S.
 

·
Registered
Joined
·
5,605 Posts
Not sure what JM is seeing that I'm not or where he has seen dexcool the same color as ATF? Most people call it orange, even when its dirty I would not call it red. I suppose dirty dexcool and dirty ATF could be a pretty similar color but I don't think I would call that red either, more of a nasty brown.

I'm having a little trouble orienting myself to the photos but I'm pretty sure we are looking at the transfer case and the front output shaft. Which means there is nothing above it to leak down on it. What is throwing me a little is I thought a 99 had the 'auto' case which I thought had a splined output for the front? Also an 'auto' case should have the blue auto trak fluid in it. And by auto I mean there is a 4th button that says auto for the transfer case controls.

I think I would be checking the level in the transfer case. It should have 2 plugs facing the rear of the truck. The higher one is the level / fill port. Remove that and see what comes out. If you get a decent amount of fluid out of there while the truck is level I would first ask if you have been in deep water? If that is possible then I would drain it and see if there is signs of water in the fluid. If its been sitting it should settle to the bottom and come out first. If you have been driving it will be like a milkshake. If there is no water but its overfilled then I suspect you have badly failed seals between the trans and transfer case letting fluid leak from the trans to the case and you should check the trans to make sure its not low.

If the levels are all fine then its got to just be shot seals. I don't think this is a super common issue with these and would worry that it was caused by a bad U joint or out of balance driveshaft and has now worn the bearings in the case.
 

·
Registered
Joined
·
217 Posts
That's gotta be from transfer case I would think although the orientation of the photo does make it tough. Transfer case uses ATF so that's the likely culprit.

Steve
 

·
Registered
1995 GMC Suburban
Joined
·
17,908 Posts
That's gotta be from transfer case I would think although the orientation of the photo does make it tough. Transfer case uses ATF so that's the likely culprit.

Steve
This post reminds me of something.
Is that the u-joint under the truck (oil filter adapter) or the one connected to the t-case?
If it is the one at the t-case, then Steve is correct, it is probably t-case which uses the trans fluid.

Thanks for the clarification by 57 on Dexcool that is not red.
I have never used them, I had a friend left me some a long time ago (15 years ago) and the label was red so I assume the dexcool was red.
 

·
Registered
Joined
·
217 Posts
This post reminds me of something.
Is that the u-joint under the truck (oil filter adapter) or the one connected to the t-case?
If it is the one at the t-case, then Steve is correct, it is probably t-case which uses the trans fluid.

Thanks for the clarification by 57 on Dexcool that is not red.
I have never used them, I had a friend left me some a long time ago (15 years ago) and the label was red so I assume the dexcool was red.
It's definitely the u-joint at the T-case. If you look past the cross member (left) you can just see the driveshaft next to the trans pan headed north to the front diff.

Steve
 

·
Registered
Joined
·
22 Posts
Discussion Starter #7
Thanks for all the great input guys!

I'm kinda leaning toward the seal at the transfer case shaft - like in this video

I think it coincides with the symptoms I'm seeing. I'll be ordering a new seal from RockAuto. As I live in Norway, it will probably take a while before it's here though.

What do y'all think?
 

·
Registered
Joined
·
5,605 Posts
Did you check the fluid levels in both the t case and transmission? Even with good seals they will leak bad if they are overfill and its darn near impossible to overfill a tcase by accident so if its overfilled there is a bigger issue somewhere causing it.

Does this have the 'auto' button as a control option? If so its supposed to use the special blue AutoTrak fluid. Something special about it that keeps the 'auto' clutch in that model alive. Supposedly its just synthetic ATF but its not like it takes gallons of the stuff so I play it safe and buy the official GM stuff. I actually use it in all my t cases because its blue. Easier to tell what is leaking when you find spots or puddles.
 

·
Registered
Joined
·
22 Posts
Discussion Starter #9
57diesel: I haven't noticed an "auto" button - is this in the cab? I have a 4W selectable.

I've been doing some reading in the service manual and found this

637439


I haven't filled anything except for the engine oil - used a different viscosity than previously though.

I'm gonna check my vent hose, see if I bent it weird somehow. Then I'm gonna go over the transfer case bolts.
 
1 - 9 of 9 Posts
Top