HELP - 1998 K1500 - Rear Differential Fluid Identification

Looking for help identifying the fluid type in the 1998 K1500 rear differential.
It is a 3.73 locking diff.
Strangely enough, even though supplied with the VIN non of the dealerships
are able to tell me what type of fluid to use. Everyone has just said 90W gear oil. Some have said it may be synthetic as well.
I also had a parts person tell me to add a special bottle of GM additive for locking/limited slip diffs that is supposed to reduce chatter (which I'm not even hearing).
Can anyone help me identify the type of fluid used in the diff. and also comment on that small bottle of GM additive that was recommended to me? Thanks.
Forest
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

the owners manual, if you have it. I'm surprised at the dealers in your area (wherever that is), they of all people should know. Since it's a 1998, I'd guess it's synthetic, but it could be 90w gear oil. As far as the additive, if it's a true locker, like in the old days, the additive is a must or it will make popping noises and jerk the vehicle when going around corners. It'll feel like one of the spider gears is missing a couple of teeth... it's really weird. On the other hand, if it's synthetic, the additive may not be needed. I believe I'd try to find an owners manual, do some more internet research, or try to find somebody (know any professional mechanics?) who has access to a set of the All Data CD's that cover your truck.
Good Luck
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I can look it up tomorrow for you if you can wait that long
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I found the differential fluid type ... it is Axle Lubricant (GM Part No. 1052271) or SAE 80W-90 GL-5 Gear Lubricant.
It does not make any mention of whether it is synthetic or not. It also does not mention anything about an additive.
Thanks for the response.
Forest

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I'm pretty sure GL-5 is not a synthetic. But I would make sure to put in the limited slip additive.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

websurfer wrote:

================== I disagree.......do NOT use the additive.
GL5.....aka 80W90W is the correct fluid type....and is not synthetic.
~:~ MarshMonster ~:~
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Yeah, but going to a full synthetic is in no way going to be detrimental, in fact for severe service it's definitely the way to go.
Look on a bottle of Mobil 1 gear Lube. It will tell you that it is suitable for all differentials, including limited slip, which I'm sure that's all that is in your '98 chevy truck, and not a detroit locker. mark
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Mark D wrote:

========================== I agree.
Fact.....not fiction.
~:~ MarshMonster ~:~
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.