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Unread 01-22-2011, 09:37 AM   #1
Ken4444
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Correct type of fluid for AMC 20 differential?

What is the correct type of fluid for the AMC 20 differential? And does anyone have any specific part numbers?

Jeephammer reccomends "80-85 gear oil" fluid in this post. Another person reccomends "AMSOIL Severe Gear 75W-90AMSOIL" in this post. This post also reccomends about half a dozen other general types.

I would tend to trust Jeephammer's reccomendation, but where can I get 80-85 gear oil? A search of the Napa website is of no help, so I'm turning to you guys. I see threads often here of people rebuilding axles, so certainly someone has some part numbers handy! I'm sure this will turn out like those posts of people asking what fluid to use in the T5

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Unread 01-22-2011, 09:54 AM   #2
brownbagg
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any walmart will have it, any 90 wt will work. its nothing special
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Unread 01-22-2011, 10:01 AM   #3
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After fixing the drivers side bearings and putting in Mosers, I did the AMSOIL in mine, so far so good.
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Unread 01-22-2011, 10:06 AM   #4
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80W-90 I think would be fine...
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Unread 01-22-2011, 10:12 AM   #5
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Quote:
Originally Posted by skidplate77 View Post
80W-90 I think would be fine...
yep! Just plan ol' gear oil. I used GL5 in mine. 75W-90

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Unread 01-22-2011, 10:47 AM   #6
Ken4444
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Okay, I looked in the 84-86 Factory Service Manual and it states:

"SAE 75W-90 API Grade GL-5 quality...
2.25 liters (4.75 pints)"

So can anyone provide a part number from a specific manufacturer?
amc20-lube-specs.jpg  
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Unread 01-22-2011, 01:21 PM   #7
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Ken, you really can't go wrong with any of the big name oil/lubrication companies for a conventional (non-synth) GL5.
My Dana 300 just loves Valvoline.


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Unread 01-22-2011, 04:55 PM   #8
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it just plain 90 wt, any walmart, auto zone, advance has it
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Unread 01-23-2011, 07:59 AM   #9
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Spend the coin and go full synthetic. Far better rolling resistance, lower operating temps, thicker dynamic wear cushion. Chevron Delo Synthetic 75/90 . . . $140 retail for 35lbs (5 gals) I would change out your Dana 30 also. And did I mention . . 500,000 mile recommended drain interval ? I believe Shell and Mobil sell it by the qt / gal where as Chevron/Texaco does not. Any heavy duty truck parks store should have it or I know the trucks stops like Petro , Pilot , or Flying J shelf it but you would pay an inflated price there. I pull my Chevron product out of Port Artur and know many distributors in the Houston area.
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Unread 01-23-2011, 08:20 AM   #10
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For the AMC-20 the important thing is using a "GL-5" 75+/- to 90+/-W oil. The GL-5 classification means the oils has the correct Extreme Pressure" (EP) lubricants for the ring and pinion gears.

Choose your favorite flavor of oil, and change it regularly- 10,000 miles or less, or after any "under water events". The reason we change the gear oil is to remove accumulated dirt and water.

If you have a "track-lock" clutch type posi differential, be SURE to use the "track-lock" additive in the oil...

IGNORE any discussion of "extended drain intervials", "Synthetics are good for 500,000 miles", etc. Any gear oil that you use will last forever. The problem and the reason for short change intervials is the oil gets dirt and water in it, from the way most Jeeps are driven. Remember, the AMC-20 has an unfiltered vent line that allows air (with dirt and moisture) to move in and out of the differential.

Oh, don't use the GL-5 gear oil in your transmission....
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Last edited by halpeters; 01-23-2011 at 08:29 AM.. Reason: added comment about additive in the oil
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Unread 01-23-2011, 08:24 AM   #11
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Quote:
Originally Posted by rustedcustom View Post
Spend the coin and go full synthetic. Far better rolling resistance, lower operating temps, thicker dynamic wear cushion. Chevron Delo Synthetic 75/90 . . . $140 retail for 35lbs (5 gals) I would change out your Dana 30 also. And did I mention . . 500,000 mile recommended drain interval ? I believe Shell and Mobil sell it by the qt / gal where as Chevron/Texaco does not. Any heavy duty truck parks store should have it or I know the trucks stops like Petro , Pilot , or Flying J shelf it but you would pay an inflated price there. I pull my Chevron product out of Port Artur and know many distributors in the Houston area.
Nothing wrong with synthetic. You either live by it or you don't. It's good stuff, but unnecessary. No insult intended. Standard gear oil is more than satisfactory.

Quote:
Originally Posted by Full Tank View Post
Ken, you really can't go wrong with any of the big name oil/lubrication companies for a conventional (non-synth) GL5.
My Dana 300 just loves Valvoline.


FT
Agree...

Quote:
Originally Posted by Ken4444 View Post
Okay, I looked in the 84-86 Factory Service Manual and it states:

"SAE 75W-90 API Grade GL-5 quality...
2.25 liters (4.75 pints)"

So can anyone provide a part number from a specific manufacturer?
Pretty much what FT says... Any of your parts stores will have it, WM, etc.
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Unread 01-23-2011, 08:50 AM   #12
Ken4444
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Thanks to everyone for the input. The information was helpful. Diff fluid seems to be much more common than gear oil for my T-5. Here are some photos and commentary of the fluid fill job if anyone is intersted.
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Unread 01-23-2011, 09:16 AM   #13
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That pic saus it all, thank you
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Unread 01-24-2011, 05:24 AM   #14
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Please don't IGNORE the fact that the lubricant recommendations for your jeep is based on almost 30 yr. old technology. Will any XYZ gear lube work?
Of course. Do you want to minimize wear in your gear boxes and motor? Then don't IGNORE the advances that petroleum engineers have made in the past three decades.
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Unread 01-24-2011, 07:47 AM   #15
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I used just plane ole 90wt. The cover was so shot from being dragged over rocks that it would need to be refilled every two weeks or so. It was like a constant lube change, so I was not going to use anything expensive. Never had an issue running 90wt and neither will you, despite what the amsoil dealer wants you to think (cha-ching)
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