Need help!! yukon denali drivetrain

[lawjack]

Okay, so for now the problem has been "fixed" but I really have no clue whats going on, about a year and a half ago my front differential finally went out. My dad and i ordered a brand new one, and had it installed, within driving the Denali for 25 miles the new differential had overheated and blown all the fluid out of itself. We sent this one back, and had a new one installed under warranty, and once again the same thing happened. We repeated the process again, and it happened for a third time.

Just to make it clear, we did check the vent tube to be sure it was clear so pressure wouldnt build. As for the past year i have just driven my Denali without the front driveshaft installed, and it does fine, but on longer trips, say 150 miles, the front differential still blows all the grease out all over the bottom of my car. We really have no clue whats going on and would love any advice. Right before it blows the fluid it feels like the front tires are rocking back and forth.

 

[ktmhans]

Hmmm,
I find it funny that where ever you are getting these rebuilt diffs keep sending you replacements.
Have u been filling 1/2" short of the fill hole or they?
Only thing that comes to mind is that some how your rotating mass(brakes,bearings,cv joints) are somehow putting some serious restriction on spinning. When driveshaft is hooked up the energy is getting trasfered foward by it and back by the something else listed above being wrong. Thus forming heat.
Your running a good mobil 1 or royal purple synthetic gear oil right.

Take the truck for 20 mile ride, then park. Imediatly start putting your hand up in there and find out if anything is warmer then it should be. This is a long shot but

Also why the hell would a shop of any sort not have looked into this problem for ya. Crazy to me

 

[M3PO]

Strange, I wonder if it could be something wrong with the transfer case. It would probably be cheaper to take it to the dealer or a good shop and pay them to diagnose, then fix. Replacing parts is fine, but you have to find the reason for the failure or parts replacement only buys times.

 

[GM-MAN]

Be interested to know what trans case you have as most Denalis are self biasing and will not drive rears if front shaft is off...RPO code?

If you are able to, as you state, it is probably failing from 'not being driven' and leaves a large rotating mass that fights within itself as stated above

 

[lawjack]

Be interested to know what trans case you have as most Denalis are self biasing and will not drive rears if front shaft is off...RPO code?

If you are able to, as you state, it is probably failing from 'not being driven' and leaves a large rotating mass that fights within itself as stated above

Sorry im kinda a newbie when it comes to this stuff, What is RPO code? but yeah ive been driving it like this for about a year and a few months.. Ive prolly put 15k miles on it with the front driveshaft out

 

[GM-MAN]

In your glove box is the RPO build decal
Look for NR3?/ 4? or NP3?

 

[ktmhans]

I know with my awd tahoe its stated that the drive shaft has to be there or it will launch the tc? Should have put that in first post.

 

[Freedom Motorsports]

I would wonder about the alignment of the differential itself when installed. If it is the same shop installing each differential and one right after another fails, I would do one of two things, either order the next differential from another source or order the same differential and have another shop install it. One way or another that will eliminate shop error or at least highlite it.

 

[lawjack]

In your glove box is the RPO build decal
Look for NR3?/ 4? or NP3?

The rpo code is np3 and np5 is right beside it

 

[GM-MAN]

NP3 is the New Process/ NVG 149
This is a Viscous Coupler biasing T-Case
, meaing it has to sense rear wheel spin to send power to the front

I was told, as many have stated, that you can't pull the front shaft as per the 60/40 split thru the planetary differential
but since you said you have done it opens a different can of worms
so
Either it is not self biasing 60/40
or
you are only running off of the 60% rear [which should have failed by now]

What was your original problem?