Yes, I know how to search the archives! :rolleyes: That's why I'm asking the question that will not die...again. :)

I have a 1975 differential with a 3.08.

According to one thread, someone used just more than three bottles of GM lube. A bottle of GM lube is 24 oz. That means his differential took 50 oz. of lube plus 4 (or maybe 8) oz. of positraction additive.

In another thread from late last year, two quarts were too much. Everyone agreed that one and one half quart bottles were all you needed to fill it up. Since a U.S. quart is 16 oz., that would mean 24 oz. plus, presumably, 4 to 8 oz. of posi additive is the capacity.

Based on this, I'm guessing that the capacity is somewhere between 28 and 58 U.S. fluid ounces. :confused: Does anyone have a more precise measurement? Maybe we can finally put this topic to rest.

I think much of the confusion comes from the use of the term "bottle" as a standard unit of measure. It's not. Some bottles are bigger than others. Please say how big the bottle you used is. And don't guess! One guy who replied to another "how much lube" thread thought he had used less than two pints - he was sure the bottles were too small to be quarts!

Maybe someone has a book?! :eek:

 

According to my 68 owners manual (page 66) rear axle capacity is 3.7 pints.
I dont think the capacity varied much (or at all) over the years, but I am not sure about that. so with 2 pints to the quart, that would be just under 1 3/4 quarts, or 2 bottles at 1 quart each should do it with a bit left over. MJ

oh, you want oz? 3.7 * 16 = 59.2 oz.

I see where you went wrong: 1 pint = 16 oz
1 quart = 32 oz !!! :)


[Modified by MNJack, 4:25 PM 4/17/2002]

 

I don't have access to my book right now, but for sure its in the mid-50 oz range. There are two things causing the problem; I've seen guys look at the GM 24 oz container and refer to it as a "quart"; second, it's impossible to get all of the old oil out of the differential unless you unbolt it. After sucking mine as dry as I could, it took two 24 oz containers and 4 oz of posi additive.

 

wow, that would be confusing! :) In my case, GM rear axle lube part #1052271 was in 32 oz bottles. MJ

 

Leave it to me to add to the confusion.

A quart contains 32 oz. Now it's all beginning to make sense. What ever happened to enthusiasm for the metric system?

I'll crawl back under my rock now.

 

Shall we throw liters into the mix, just for fun? :D
When I did mine, I needed 2 bottles of Mobil 1 synthetic gear lube, in what were (as I recall) 1-liter bottles. Perhaps they were quarts, but the difference is small. Plus, of course, that all-important 4-ounce bottle of posi additive. I used a hand pump to suck as much of the old oil out as I could, and still couldn't get all of both bottles in. NOTE: That's why you want to put the posi additive in first!!! After the posi additive, I got about one and a half bottles of lube in, maybe a little more. What's that, 4 + 32 + 16 = 52 ounces?

I just took a look at a couple of catalogs. Mid-America definitely adds to the confusion; their "kit" includes "3 quarts of GM lube" plus one 4 oz bottle of the posi additive. However, in the Zip book, the GM lube comes in "23 ounce" bottles. Zip shows a pic of the bottle, and it says "23 ounces" right on the label. And zip says it takes 2 bottles of lube plus 2 bottles of additive! So, geez... Mid-Am says it takes (32x3) + 4 = 100 ounces! While Zip says it takes (23x2) + (4x2) = 54 ounces... Based on my experience, I'd say Zip is probably closer... :D

And what about that additive? How much? 4 oz or 8 oz? Mobil 1 says you don't need any additive with their oil, so I sorta split the difference and put in just one 4 oz bottle... :rolleyes:




[Modified by Gator81, 4:44 PM 4/17/2002]

 

I went to a corvette and high-performance car show and there was someone selling Assembly and Installation Manuals (AIMs). I bought one for my 75 and it lists everything you need to know about torque specs on every bolt and nut on the car, what gets lubed...what kind...and how much. It's only $25, and makes a great shop reference. I think Corvette America lists them in their catalog.

 

This is funny :lol:
I replaced the fluid in my diff last spring. I have the leftover bottle in front of me right now.
The bottle is 1 us quart, 946 mL. It is almost exactly one half full (half empty?).
This means I used 1.5 (1 quart) bottles.
I used a suction gun to remove the old fluid, so the diff may not have been completely dry. I am pretty sure I used one 4 oz bottle of posi fluid. My hazy memory thinks the dispute was caused by 2 (2 oz) bottles vs. 1 (4 oz) bottle.

 

Ok, I know this is going to seem obtuse, but why exactly do we need to know how much fluid to put in teh Diff? Is it not possible just to fill up until the fliud overflows, or will that oput too much fluid in?

Sorry if sounds like something "Bubba" might ask, but I had to ask it!!

 

no its not a bad question and your right the only thing you need do is make sure the posi additive is first and then fill with gear oil till it just starts to trickel out. Been doin it like that for longer than I can remember :yesnod: :smash: :seeya

 

The guys at the Auto Parts store can look it up on their computer. They told me 2 and 1/7 quarts. I put one tube of Posi additive then 2 quarts of fluid. It didn't quite take all of the last quart. You will know when it's full, IT overflows out of the drain hole.
Jay

 

I am dedicated to the pursuit of measuring obscure fluid capacities. :lol:

Seriously, you're right. Pouring it in until it overflows is probably the easiest and most effective empirical methodology. However, in order to pour it in, you have to buy it first. And, if you're going to buy it, it's nice to know how much you need. Thus, we arrive at the paradox that motivated my query. :D

 

Yes, that's they way I've done it. And make sure it drips out on your exposed forearms, that way you can smell like @$s for days :eek:

 

Wait a minute! Let's ask Pedro! He just got his PhD, so he'll know for sure!

Rockn'Roll - what's the AIM say? I always thought it was 2 bottles of additive, then fill up until overflow...

 

I AM GETTING SO CONFUSED!!! AND A HEADACHE!!! :crazy:

 

GM spec. book for my '76 says 4 pint capacity. 4 pints=2 quarts=64 fl. oz.

 

ya know being careful usually does it for me but a bath can always cure the a$% smell :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:

 

Thought I'd go get some after reading this

 

So this thread is all about how much to ask for at the auto parts store :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:

 

For the record I just changed the oil in my 71 Rear. It took about 55 oz. after I put in 4 oz. of positraction additive for a total of about 59 oz.