riski

Have a 1970 and think it is time to change the gear lube.

Does anyone know the right gear lube to use?


Use Mobil 1 75W90 synthetic only.

or

Use one bottle of GM positraction additive and two bottles of GM rear axle lube.


Regards,
Rich

Tom1701

This is what you need. i don't know about the price.
http://www.ecklers.com/product.asp?p...8&dept_id=1872

Tom1701

73, Dark Blue 454

Instead of removing the cover (pain), pump out the old stuff.

Use something like this:

http://www.summitracing.com/parts/WMR-W1145/

Agree with Tom,..use the recommended conventional 80w-90 lube and 4 oz. bottle of GM friction modifier.

wcsinx

If you do go with the M1 synthetic, look for the bottles with the "LS" suffix as that indicates they already have the limited slip additive mixed in.

69small block

I used lucas gear lube and Trans-x posi additive no problems at all still smokin the tires like it used too.

jordan89

I'm about to drop in some AMSOIL Severe Gear fluid, right after I get done painting the underside of the car.

enkeivette

Redline 75w90. I didn't need the friction modifier, Redline mixes it in and they used enough where there was no locking.

riski

I am leaning toward using Mobil 1 synthetic 75W90 and add four ounces of GM Positration additive. Does anyone know if this will create a problem?

wcsinx

If you're going with M1 synthetic, why not just get the stuff with the additive already in it?



See the "LS" on that bottle? No additive needed

73, Dark Blue 454

Pour whatever you want into your differential. Just be aware, that:


Strange Engineering (who builds 1000's of rear ends),
Moser Engineering (who builds 1000's of rear ends),
Tom's Differentials (who builds 1000's of rear ends),
Auburn (who also makes a fine LS carrrier),
Dana (who makes makes a fine LS carrier for newer Vettes for instance),
And Eaton themselves, the company that designed and manufactures the LS carrier installed in your C3,

...ALL recommend against the use of synthetics with their limited slip carriers. They all recommend conventional lube with the GM friction modifier.

...Roger...

Dang I just learned something new today. I've never seen the LS before is this new ?
I've used mostly all GM for years (but 2 bottles of additive)with good results and have used other mixtures (GM additive)that were recommended by whoever rebuilt the rearend with good results also.
I'll have to try the Mobile 1 LS on some problem rearends and see how it does.

riski

73, Dark Blue 454

Can you give me any specifics on why they do not recommend synthetics?


Thanks,
Rich

73, Dark Blue 454

From here:

http://www.eaton.com/EatonCom/Produc.../FAQ/CT_128414

...is this:

(scroll down to the Eaton Posi section)

"What kind of oil should I use? Can I use synthetics? Do I need a friction additive/modifier?
Eaton Posi units perform best when using GL4 (or better) mineral/petroleum based gear oil. A four ounce bottle of friction additive/modifier is also necessary for optimum performance."

From here:

http://www2.dana.com/pdf/5323.pdf

...is this:

"Limited slip differentials impose additional requirements on lubricants,.. Some otherwise good lubricants do not preclude "chatter" or "bumping" in turning corners with Limited Slip Differentials. Many vehicle manufacturers find it necessary to specify a special lubricant or lubricant additive for use with Limited Slip Differentials. Check the vehicle manufacturer's lubricant recommendations".

From here:

http://www.auburngear.com/aftermarke...6pagesize%3d20

...is this:

(click on Limited Slip Differential Install Instructions)

...is this:

"The Auburn Gear limited-slip differential design has been extensively tested with high quality non-synthetic 80W90 hypoid oils treated with GM or Ford friction additives (3 oz. of additive will treat 1 quart of oil). To avoid differential clutch chatter (noise) and for optimum performance, use the oil and additive described above. Use of other additive and oil types may cause differential clutch chatter.

Ford Part Number: C8A219B546A
GM Part Number: 1052358"

To verify lube recommendations from those I cited who build differentials, please call:

Tom's Differentials (an Eaton dealer),..208-265-8111

Strange Engineering (another Eaton dealer)...847-663-1701

Moser Engineering (another Eaton dealer)...260-726-6689

wcsinx

Dunno, first time I used it was in my C5 a couple years ago, and there's been plenty of tire smoking and gear banging since then. Seemed to work just fine without issues.

riski

I checked the price of the GM gear oil GM #89021671 the price is $16.84 for 23 ounces.
The posi additive is $12.54 for 4 ounces.

I cannot believe what GM charges for gear oil. Also, 23 ounces is not a full quart. I may need to purchase 3 containers of the 23 ounce stuff + posi additive.

$63.00 for gear lube, is it me or is this just a total rip off.?


I appreciate the information about using GM only lubricants, but if this is what it costs, I would really like to know the following: Why are synthetics not good, What is the real problems they cause?

jordan89

You're not alone Roger. I too did not know about Mobil 1 LS before. That's why this forum is so great.

Rally68

I used the heavier weight Lucas gear oil and Trans-X. The bottle says it meets OEM specs for GM Ford & Chysler. My posi has performed flawlessly and is very quiet.

C66 Racing

Much less costly (and in my opinion significantly better) option:
AMSOIL Synthetic Gear Lube SAE 80w90 (Product Code AGLQT)

This gear lube comes with friction modifier already in it and most cars don't need more to prevent diff chatter. But if chatter occurs, this squeeze tube is easy to add a few oz of modifier and quiet the diff down:
AMSOIL Slip-Lock Differential Additive (Product Code ADATB)

For the DIYer:
AMSOIL Hand Pump (Product Code G2039)

Other than the Eaton link above, the others really don't come out strongly against or for synthetics, they just indicate that chatter may occur, which I would agree with. But, if it does, the fix is also as easy as adding a little modifier and you then have a better fluid and no chatter.

In answer to your question about what makes synthetics better, this AMSOIL study is a good read on what differentiates one gear lube from another:
AMSOIL Gear Lube “White Paper” (2 MB pdf file)


P.S. If you decide to go with the AMSOIL over the GM (or any other fluid), drop me a PM so I can ensure you get wholesale pricing, abuot 25% below retail, via the AMSOIL Preferred Customer Program.

...Roger...

It sounds like your saying the anti chatter additive is a friction modifier, I was told the additive was an anti-foaming agent.

72LS1Vette

I used Lucas gear oil and 1 bottle of GM posi additive and so far no problems or noise. The diff has ~75,000 miles on it and nothing except side seals and a yoke have been replaced that I know of.



Rick B.