Front Diff Vent Question

[Dawg]

I'm going to change front end fluid this weekend and change over to synthetic. I remember reading something about switching the vent cap.

Which end of the vent tube? I have a white fitting which is plugged into the differential. The lower end of the hose is plugged into this white fitting. The free end of the vent tube has a black cap on it. Which one needs to be changed out?

Any part numbers would be greatly appreciated. I was talking to my parts guy today about making the switch and he said he was not aware of the white vs black vent cap.

Thanks, Jamie

[DmaxMaverick]

You have the latest vent plug. The one in question is the plug, with nipple, on the diff. Black was the original, and according to GM, is not compatible with synthetic lube. The black cap on the end of the vent line is not part of the TSB, and poses no problems with synthetic lube. There is no updated vent tube cap.

[Dawg]

Great! Thanks!! Just a simple fluid exchange this weekend.

Jamie

[pgreen]

Along this line, I have a very new '05 3500. I want to change the rear and front end fluid after about 1500 miles (this weekend?) What is the preferred diff oil, and how much? I'm assuming full synthetic is OK in the late '05s?

Thanks!

[jbplock]

Originally posted by pgreen:
…I want to change the rear and front end fluid after about 1500 miles (this weekend?) What is the preferred diff oil, and how much? I'm assuming full synthetic is OK in the late '05s?

Thanks! Pgreen,

Assuming you have the Eaton (G80) Locker GM specifies a synthetic 75w90 GL5 lube for the rear end (also known as “Grape Juice”) for about $26 per quart at the dealer. Last I knew no one had found an aftermarket lube that “explicitly” meets the GM spec. However, many of us are using other 75w90 synthetics such as Mobil-1, AMSOIL and Redline. You can also use these lubes in the front diff as well. Some who are towing very heavy loads use a synthetic 74w140 GL5 in the rear diff. Try a forum search on “rear diff” for more info… Here is one example…

Eaton's Recommendations on Locking Rear Diff Service (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=7;t=002814)

smile.gif

[pgreen]

Originally posted by jbplock:

Last I knew no one had found an aftermarket lube that “explicitly” meets the GM spec.

That is exactly what I was wondering... Thanks!

P

[Dawg]

Easy swap!!

Drop skid plate. Drain and refill. I have a long clear hose that attached to the fluid bottle. Just plug it into the fill hole squeeze.
Took and 2 1/2 quarts.

Thanks