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Differential to be changed ?

BlueWarthog

Full Member
Joined
Dec 1, 2015
Messages
316
Location
France
Hi guys,

few weeks ago I was asking you some advices in order to change front differential axles shaft seals (left & right).
It has been done and we have changed the differential fluid. The oil was very degraded, almost solid with a lot of fillings in.

Few weeks later I can see that the 4x4 doesn't work anymore. Tha's bad.
The torque comes from the rear side, it's okay.
The 4x4 "engager" motor works fine (so the electrical system is okay). We've also tried by pushing the "bolt" with finger. 4x4 doesn't engage.

So my garagist conclusion is to change the differencial. It does not make me laught but I probably have to proceed.
So here my question :

I see on my RPO Codes GT4. I think it means a gear ratio 3.73 : is that correct ?

I thank you very much, have a nice evening.  (y)

 
you should be able to open up the differential and look at it.

For it to not work meanss either pinion or ring gear or both have all their teeth grinded away... which I find hard to believe unless it was over loaded and "EXPLODED" but that tends to be the rear.

I suggest removing cover and inspecting before you go buy all new one.

Lift truck up and tires off ground.
start engine.
Engage 4x4 and see what happens.
Rear wheels turn?
drive shaft out of Transfer case turn?
Front wheels turn?

any noises?
 
Thank you Ygmn,

it hasn't been overloaded or exploded, that's just nothing happens. I mean rear wheels turn, but front wheels do not.
The eletcric pushing motor works and engage the little bolt, but inside the diff nothing changes and front wheels do not turn.
Any noise, nothing.

Yes I have got the choice :
- just to disassemble the diff and take a look inside and check everything.
- or just pull it down and replace it.

Actually it probably will cost me less expensive to replace it than look for error.

Another thing helps me to think this way is the oil was very very loaded with a lot of fillings. Before this maintenance the diff has a noise when 4x4 engaged, and more when low 4x4 was.
I think the diff was tired before this and the last operation has "got the better" of it.
I probably will have to change it soon, with the garagist work to pay once again... so I should probably do it now.
 
But you're right, it's probably a "little thing" because nothing happens at all : it's just not engaged. Maybe just the little finger bolt is broken !?  ???
 
something in transfer case.....

again do the test with it up in air to see what spins and what does not
 
Given the filings found and the lack of proper operation, why not just have that front diff rebuilt?

I had all of my internal parts replaced some time ago and have been very happy with the results.
 
Something broke in my front diff. Banging and clunking with 4wd engaged (even Auto). I pulled the inspection cover and can see dings in the ring gear, left hand bearing is loose.

Local wreckers has one off a Yukon. Mine has rear axle RPO code GT4 (3.73 ratio). Am I correct that so long as the Yukon has the same rear RPO code, the front should work?
 
ygmn said:
you should be able to open up the differential and look at it.

For it to not work meanss either pinion or ring gear or both have all their teeth grinded away... which I find hard to believe unless it was over loaded and "EXPLODED" but that tends to be the rear.

I suggest removing cover and inspecting before you go buy all new one.

Lift truck up and tires off ground.
start engine.
Engage 4x4 and see what happens.
Rear wheels turn?
drive shaft out of Transfer case turn?
Front wheels turn?

any noises?

Same problem with my 2003 1500 Z71 Avalanche. 

Lifted back tires turn in 4hi and 4 lo as well as the driveshaft coming from the transfer case.  Actuator functioning as should but "pusher finger in front diff" only moves 1/8" when pressed manually with a punch/socket extension.  No noises or other issues. Changed fluids and no unexpected buildup of metal on plug. Truck only has 124,000 miles so I am stumped.  There is no real inspection cover to speak of on this unit so i guess dropping the assembly is the only option to inspect?
 
Wildcat96 said:
There is no real inspection cover to speak of on this unit so i guess dropping the assembly is the only option to inspect?

On mine, there is a ~2-1/2" diameter dirty white plastic threaded plug with a vent hose on the left side of the case, midway between the mount and the left axle. Access requires removal of the front left wheel. It is threaded in and can be unthreaded with a 3/4" deep socket once the hose is removed.

Can't see everything, but a borescope helps.

Note that I found it very tricky to thread back in without cross-threading. Be very careful with those plastic threads!

front_diff_cover.jpg

 
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