G80 code fluid change, additive or no?

[olliec420]

So in my 98 Yukon with G80 code, I have a rear axel seal leaking and am going to service rear end. Bearings, seals, fluid, gasket. From the AMSOil site, I have two quarts 75w-90 (ACD 10-4016) in my cart (ACDelco fluid, just using AMS site for amounts) but am conflicted if I need to order and add ACD Limited Slip Additive or not (ACD 10-4003)? Can anyone advise?

 

[Doubeleive]

it does not require it, there is lots of "speculation" about using anyway it depending on who you ask
I have used it on g80's and it quieted/stopped unwanted lockup and I never had any problems.

 

[olliec420]

it does not require it, there is lots of "speculation" about using anyway it depending on who you ask
I have used it on g80's and it quieted/stopped unwanted lockup and I never had any problems.

I guess for $10 its not a big deal. Just didn't want to add it if I dont need it. I'll add. Thanks.

 

[tungsten]

If you read around its not a limited slip per say,G80 is a mechanical locking diff.

I think if you asked 10 GM techs all would say no don't add it.

 

[olliec420]

If you read around its not a limited slip per say,G80 is a mechanical locking diff.

I think if you asked 10 GM techs all would say no don't add it.

Well its $7 with the rest of my order at Rock Auto. I guess I'll buy it and not add unless I have a problem. $7 is worth it to have on the shelf.

 

[tungsten]

Well its $7 with the rest of my order at Rock Auto. I guess I'll buy it and not add unless I have a problem. $7 is worth it to have on the shelf.

I did some looking/reading a few yrs back and there really was no definite answer that I found. I dont add anything.

 

[bsamole]

My 99 Tahoe had a complete rebuild of the rear end from a drive line and gear service company. They replaced everything from both U-Joints, all bearings and the posi. They used part number A/G546097 (GM8.5/8.6 POSI 273 & UP 30SP) $590.91 for the posi. They used 80/90 GL6 (Bulk) for oil and no other additives. For you reference and justification for doing the job yourself I spent $965.16 for parts and the labor was $786.25.

 

[east302]

There’s a TSB somewhere saying not to use friction modifier but I can’t find a copy of it now. Best I could find was this link:

Locking rear axle (G80) - use additive? - Chevy Message Forum - Restoration and Repair Help

Chevy Forums FREE technical assistance for your restoration and repair. Model specific subject matter experts, classified ads and more.

www.chevytalk.org

 

[wjburken]

@Rocket Man @iamdub

Didn’t one of you do a Ph.D level dissertation on this subject and find that additive was definitely not needed on a G80 locking differential?

 

[George B]

@Rocket Man @iamdub

Didn’t one of you do a Ph.D level dissertation on this subject and find that additive was definitely not needed on a G80 locking differential?

Someone did but I don’t recall who.