Changing Differential fluid
 

I am going to change my differential fluid soon because I am not sure if it has ever been changed before. It is a Borg and Werner 2.77.(9bolt) I had a couple of questions before I attack this myself. I would like to know what kind and weight of gear oil to get and where I can get it. I made my way out to Autozone, Murrays and PepBoys and all they had was the same brands as they had oil.
To my knowlege all you do is unbolt all 9 bolts let the fluid drain into a pan. Now do I use RTV sealant to make a gasket and then put the cover back on and fill with fluid from the top?
Do I need to clean the rest of the stuff out with a rag or with carb cleaner? And do I need the additive and where do I get that?
If anyone can give me some tips I would appreciat it.
Thanks:)

i prefer a gasket over rtv. i might use a little brake clean and air to remove some oil, sludge, and chips. if you hasve a clutch type posi you need gm posi additive. i use mobil1 or amsoil gear oil.

Ok. Where do I get the GM posi additive and the gasket? Do I have to go to GM?

The GM posi additive is the most dependable kind. Although, I've heard rumors that they've discontinued it. But really, and brand will work fine.

The gasket doesn't have to come from GM. Use the tubular style gasket.

What is a "GM clutch type posi"? And how do I know if I have it? I have a Borg-Warner 9 bolt too with posi-traction, but can I just using normal gear oil that is made for limited slip diferentials? What weight do you recomend? Thanks. -89IRO

if your sure you have a posi then you need the additive, you add this with the regular gear oil when you put it in the rear end. I am in the middle of installing 3 series gears in on my 2 series posi unit and already bought the additive from GM $7.49 I think it was. just go to a dealership and ask the parts guys for it.

So if I know I've got the GM posi-unit (borg warner 9 bolt), I use the regular gear oil (what weight?), even though it says it is for limited slip, I still have to use the additive from GM? This isn't a problem, just a litte confused here. I think I know what you're talking about, it's in a silver bottle right? Oh, and how many quarts of oil do I put in the differential after I drain it? Thanks for the help. -89IRO

Use 80W-90 or 75W-90.

Virtually no gear lube you can buy off the shelf has the additive; read the label closely, and read what it actually says not what we all wish it says; it says something like "compatible with LSDs", not "includes LSD additive". So, yes you can use synthetic if you want (I do in mine), and yes you still need the additive.

It should take just about 2 quarts plus the additive. Put the additive in first, then fill it full with fluid.

O.K., thanks for the help. What is this "GL-4" and "GL-5" talk I keep hearing about? Are these two different types of gear oils? If so, which one do I want? Also, why would anybody want the kind of gear oil that is like 140 weight-- I mean isn't that like too thick? Maybe it is just for really hot climates. I think I will just get two quarts of valvoline synthetic 80w-90, but some people say to use the GM additive but others say not to use it, so I'm still not sure if I'm going to use it. Just don't understand this GL-4 stuff. -89IRO

The GL-5 spec is newer than the GL-4 spec. It's the same juice, for all practical purposes, since if fluid meets the -5 spec, it also meets the -4 spec.

You need the additive. Your rear will groan and chatter going around corners if you don't use it.

People use the 140 weight stuff for the same reason they put 50W motor oil in a stock motor..... they don't know any better. Ignore them and do the right thing.

Valvoline 80W-90 synthetic is a reasonable choice.

Hey, thanks for all the help man, I really appreciate it. So you're saying I don't have to worry about this "GL-4 and 5" stuff? -89IRO

Or you can use the redline gear oil, which already contains an additive. The GM stuff has been discontinued, I can't get it from a local dealer, but perhaps some mail order guys may still have it.

Doesn't valvoline make their synthetic gear oil with the limited slip additive already in it too?

No, it does not. Read the label.... you will see that it reads as I described above.

Not that I would know anything about Valvoline though; my only exposure to them is that my wife worked for them for about 20 years.

According to Valvoline, it does.

http://www.valvoline.com/pages/produ...asp?product=58

Check the fourth "bullet".

Interesting that they would say that... when my wife worked in the plant where it was packaged, it didn't..... every time I've ever used it I added the friction modifier..... when she had her rear end fluid changed to that in a car she used to have that had posi, it groaned and chattered and carried on, until she went back to them (VIOC) and had a bottle of additive added...

Not that I'd call them a liar or anything, she hasn't worked there for a little over a year now, maybe they've changed it.

It should take about 2 quarts. I personally run Valvoline with the GM additive in every 9 bolt! Gaskets are available at www.9bolt.com Also, the 9 bolt is a cone style clutch differential.

Miles
Diff Solutions
www.9bolt.com

I heared some people say that the posi additive was discontinued. If this is true, what would I use in place of the GM stuff? I guess I could get the synthetic valvoline stuff, but I am just curiouse to what I would use with normal gear oil. -89IRO

Other manufacturers sell the additive. From hearsay, I've been told the additives by manufacturers like Redline is the GM additive in a different bottle. I do not have any facts to verify that though, and I really don't care if it is or isn't as long as it works.

You can get the fluid from redline.

RED LINE OIL
Limited-Slip Differential Friction-Modifier/Break-in Additive

or you can use Redline 75W90 which already contains the additive. The Redline 75W90NS product does not have the additive, but that oil is for non-limited slip axles.

I'm only mentioning redline because that's the product I have experience with since I haven't been able to get the GM additive. Prior to that, I used the GM additive and any gear oil I wanted.

What do you use to get the filler plug out of the differential? I see for my car it's a headless square plug that is 1/2". Where do I get a socket or tool to pull that thing out?

Use a socket with an extension and then unscrew it.

Edit: meant ratchet.

Should be able to just use a ratchet with no socket to get that out. BTW, I just picked up a bottle of the Limited Slip additive from my local Chevy dealer today. Just go in and ask for it. If you're not sure what kind of rear you have check the RPO codes. G80 is the code for Limited Slip. :)

Hope that helps a little.

89IRO quit your winny question askin and go do the d a m n job already!!! :p

Hey Thread Hijackers:p I ended up changing my gear oil using rtv sealent, gm limited slip additive($13):eek: and some mobile 1 gear oil. THe first time I made a crappy gasket and it leaked so I had to do it over again.

This document for Mobile 1 implies that Mobile 1 also has the limited slip additives if I'm reading it correctly. I used Mobile 1 80W-90 in the posi in my '69 GTO and never had any trouble with it. I now use Mobile 1 ATF in my T-56 :D

-Paul

89IRO quit your winny question askin and go do the d a m n job already!!!

shut up

89IRO: You may want to look at the American Petroleum Institute for the GL-4 rating. I have a link to the meaning of the classification at http://api-ec.api.org/filelibrary/glchart.pdf

Josh- thank you for that info. Today I just put in about two quarts of Valvoline 80W-90 dino oil. I got new bearings and seals put int the axle as well as a new gasket. I took her for a drive and it was great! Smooth as can be and no noises. No thank you GM posi-additive! Someone just told me today you aren't supposed to put the additive in 9 bolts anyways. -89IRO

89IRO, how hard was it to replace the bearings? Did you replace the rear wheel bearings? I get a lot of funky noises from the rear which I was told could be just wear and tear. Thing is I have almost 162k miles on those rear wheel bearings and I bet they would like to be replaced. I read about how you pull a bolt out of the differential and then pull the axles out but it seems like I could easily mess something up in there.

Actually my mechanic did it. It took him only one day to do it. Just remove your brakes, then there is a plate with four bolts I think that you remove, then the axle just slides out. There is no c clips on the 9 bolt to remove so you don't even need to take the differential cover off. My mechanic did have to take the axles to another shop to have the bearings pressed, but after that, you just throw on the new seals and put it all back together. But yeah, you'll need a shop for the bearings. Then just fill her up with new fluid. That's all that's to it. I wasn't having any noise problems before I had it done, but it was leaking all over, so it was just time to have it done. Later. -89IRO

How much did it set you back to have the mechanic replace the bearings?

It all came to $400 but all that included: Bearings, seals, gasket, new plug, speedo cable lubrication, and him taking it to an alignmet shop for me since I got new BFG KDW tires and I want them to last! Plus, all the labor. Really, that isn't much money compared with a new rear end! Plus, I got more stuff done to it besides just the rearend so it wouldn't have been that much to do just the rear. Just do it all yourself and take the axles to a shop and have them pressed. You'll save a lot. -89IRO

Re: Changing Differential fluid
 

Here is what I did: