Differential Fluid Change Quick Question 69 gto
 

Hi,

I have some synthetic 75w 90 Gear oil and want to change the fluid on my 10 BOLT Differential.

I've never opened it up before but it is not a "C-CLIP" version.

It was once identified by a PY member as:

>>Yes, your rearend is an Olds rearend. Well, it's actually a
>>corporate
>>rearend, in that it was used on Oldsmobiles, Pontiacs and Buicks
>>of the
>>same era. It's the 8.2 10-bolt.

My question is : do I just add one bottle of this ? There isn't any special mixing procedures?

Just put a bottle of gear oil in, then empty this in, then reset of gear oil to top of fill plug?

Then drive.

ACDELCO - 992694 - Differential Oil Additive
(pic in post )

One bottle is enough. Add the additive first to make sure you have room for all of it. After the fluid change find a reasonably empty parking lot. Drive the car in several tight figure 8's first in one direction and then the other. The figure 8's get the fluid in between the moving parts. This was recommend by the factory.

Ok , thanks goatracer1. I'll do that . Gonna go buy it now.

Ive read quite a few times that synthetic fluid isnt recommended for these rear ends... Richmond or maybe it was Yukon said to not use synthetic when I bought new gears for my 10 bolt. I would look for some standard valvoline or other brands & use the GM limited slip additive. Or at least ask about using synthetic to a local driveline shop or members on here that know rear ends.

Mine is behind a 500+hp engine that does see some drag strip use, but even for street use Ive read to not use synthetic for these older rear ends... not sure why but Ive had good luck using non synthetic.

I have done this a few times over the years on my 10-bolt second gen. I use the AC Delco additive 992694 for the limited slip. And a couple quarts (+/-) of SAE 80W-90 NON-SYNTHETIC after the additive, until it starts drippoing over. Instead of goop I use a Felpro RDS 55028-1 gasket (less messy.

Hi!

The reason for opening it up was 1) old fluid from 1999 2) because of 1 wheel burnout when it should be 2 wheels

Posted about it back 2019 where we were not sure if it was "Cone/clutch/Eaton..."

My thread : https://forums.maxperformanceinc.com...t=differential

It sounds as if it needs posi clutch packs but before i take it to a differential shop I would just to know what I'm looking at for fixing. At least learn about the repair.

Can anyone tell me a bit about the unit that is in this ?

I realize it is not c-clip version, wish it was as then I'd remove the unit and inspect further.

Where I live I can't leave car on driveway and pull axle's. So before it goes to a shop I really want to know what sorta "labour hours" are involved if it simply is a clutch pack R&R.

Thanks for help everyone.

Just looking in

That's a stock style 4-pinion cone type posi, no clutches. They can be rebuilt but I would replace it with an Eaton posi.

http://www.jdrace.com/ . This guy remachines the cones in the style posi that you have . He did mine last year for $150 + shipping . Works great - I also don’t beat the snot out of it . Synthetic fluid also doesn’t play well with the cone style unit . I learned that the hard way and I’m a big believer in synthetics .

Well I'm glad i asked before dumping in the synthetic!

I will buy 3 bottles (1L) of the GL5 Non synthetic Gear Oil 80W90.
https://www.lucasoil.ca/products/hea...w-90-gear-oil/ and then add that additive.

Tomorrow I will put the car in "N" while front tires are blocked.

Then will turn rear tire again. Make sure both still turn , I want to revisit the weird rotation problem I mentioned in the other post. As I turn the tire 75% of the rotation is resistance then 25% of zero resistance. maybe it's 60/40.

Thanks again I'll post my results.

Incidentally the website says it for sure is an oldsmobile skylark or GS rear end!
http://www.jdrace.com/content/diff_id/10bBOP_Buick.php

Posi
 

The picture shown of the Posi Unit, is it the same as a 4 pinion SuperDuty Safety Track found in a 1968 GTO?

Thanks, just gathering my quotes to rebuild this or upgrade to Easton Posi Unit and service the whole differential.

Incidentally, not sure if this is a clear sign or not but just like last time :

Turning the rear wheels CW (while in Neutral suspended) is quite difficult and resistance changes throughout the revolution of tire, same on both sides. Not sure if that is sure fire indicator that posi is worn but my friends 69 gto turns a hell of a lot easier and same resistance throughout the whole revolution. Just learning here.

Thanks again everyone.

are you getting brake drag while turning?
What if you turn one wheel and have someone try and hold the other?

Good question! no - the brake shoes and drums are 100% mint and all brand new hardware, a shop machined them 15 miles ago. Adjusted perfectly. It literally i guess is the cone but it would be nice to have a helper hold the tire and try what you suggest!

As well as a helper turn the tire while I inspect the crown and pinion turn with a bright light etc. Maybe I will see something.

I think it's called a heavy duty 4-pinion posi, used with gear ratios of 3.36 up to 4.33. The rear ends could be upgraded with Nodular iron center sections instead of regular gray cat iron.

The 68 service manual states to test for correct operating of the safe-t-track , raise the car , place in park if an auto or low gear in a manual and attempt to turn either wheel by hand. It should be extremely difficult if not impossible to make it slip , requiring around 400 lbs of pull . Mine required very little force to slip . For $150 back on the road while I figure out long term what I want to do with the differential . Give Jim a call , he’s a pretty cool dude .

I don't think mine is a safe-t-track since it is an oldsmobile rear-end? I have an automatic. I'm just waiting for some quotes to come back to decide, I emailed "jim" but must be busy.

With my car in park is pretty well is impossible but what the heck i never "fully fully gave it my all " didn't know it was a test. thanks for your help.

I did 2 videos:

In Park: ( hard to turn ) : https://tinyurl.com/IN-PARK-HARD-TO-TURN

IN Neutral ( easy to turn ) : https://tinyurl.com/IN-NEUTRAL

Is this enough evidence to 100% verify it is shot? Thanks for helping me learn.

Thanks again.

I think that’s shot . 1st vid was pretty much how mine was . Now since the cones have been machined , I can’t put enough back into to slip it . Atleast not down low on stands . Before when it was weak , it would grab/grip somewhat unpredictable. It puckered me up once and felt like it was going to get squirrelly at the track once . That’s what caused me to investigate and called Jd race . 1st he told me to get the synthetic out of it and it did grip better but meh . And when I say I was at the track , I wasn’t side stepping it off the line and power shifting ! I was just down there to run her out and pulling in 2nd , it felt like one wheel quit gripping and the rear wobbled .

Yah. so far I've learned : it's a cone style stock posi rear end, has no clutches. May or may not be rebuildable, only way to know is to send it in.

thanks locom. It does appear the cone's are worn out .

here are the tests that I assume validate:

1 Even if i put it in a gear, turn the drive-shaft by hand only one tire turns.

2 In Park, turn one tire CW other turns CCW
3 In "N" only the tire i move moves. other one stays stationary.

I mean everything points to it be broken. doesn't it.
maybe jim could confirm before pulling it if i decide.
thanks