72 differential oil/fill line? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dukcaln · 08-03-2011, 05:05 PM

what do you all suggest for differential oil and how much do I put in... is there a fill line or something... I am getting ready to go out and take cover off cause it is leaking from bottom (since I bought truck) and re-seal. Then put new oil in..... what do you all suggest, is there a simple way to know when it is full

TobyArnot · 08-03-2011, 05:12 PM

Me too!!

bosco200 · 08-03-2011, 05:14 PM

3-4 quarts, Royal Purple is good stuff

racer57 · 08-03-2011, 05:15 PM

Always been told fill it until rear end oil comes out fill plug.
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Posted via Mobile Device

fastwillie 696969 · 08-03-2011, 05:24 PM

remove the drain plug first before poppin the cover off ,basic open diff. 2qts 75-90 w gear oil Quaker state or Lucas lubrication ,take a ball peen hammer and slight tap the bolt holes flat and clean off surface to prep for silicone gasket sealer ,install the cover with the rtv ,tighten the bolts 20 ftlbs ,add oil to the drain hole on the side of the rear just when it drips out put the plug in
if its posi used the synthetic oil

AirSpeed · 08-03-2011, 05:24 PM

Quote:

Originally Posted by racer57

Always been told fill it until rear end oil comes out fill plug.
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Posted via Mobile Device

That's always been my understanding, fill it up until it runs out.
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dukcaln · 08-03-2011, 05:51 PM

cool thanks..... I don't think it is posi, unless it came that way from factory... I think it is the factory 3.73

eagleuh1 · 08-04-2011, 11:54 AM

Put the additive in for Posi too if you have a posi. I like to overfill mine a little so it runs out to the axle tube ends. I just force it in after it overflows a little then put the plug in real quick. Jim

**RenoKeene** · 08-04-2011, 12:05 PM

Quote:

Originally Posted by eagleuh1

Put the additive in for Posi too if you have a posi. I like to overfill mine a little so it runs out to the axle tube ends. I just force it in after it overflows a little then put the plug in real quick. Jim

What brand of synthetic do you use and what additive?
Thanks

dukcaln · 08-04-2011, 12:10 PM

thanks guys got it all done....

cdowns · 08-04-2011, 12:41 PM

Quote:

Originally Posted by RenoKeene

What brand of synthetic do you use and what additive?
Thanks

i use royal purple 2quarts for a 12bolt rear// no drain plugs on a 12bolt/ no additives required with royal purple or most synthetic gear oils nowadays

check the bolt holes of the cover and make sure they are flat overtightening causes them to "bell" out and cause poor sealing and leaks

craig7070 · 08-12-2013, 11:41 AM

Do you put the new cover on almost all the way they add oil if you have the 12Bolt?

Bigdav160 · 08-12-2013, 12:05 PM

There is fill plug on the pinion side. Takes a 3/8 square drive to remove.

Synthetic gear oil in the rear axle is a perfect application.

craig7070 · 08-12-2013, 01:34 PM

Quote:

Originally Posted by Bigdav160

There is fill plug on the pinion side. Takes a 3/8 square drive to remove.

Synthetic gear oil in the rear axle is a perfect application.

Thanks Bigdav160

NCBowtie · 08-12-2013, 08:00 PM

YMMV but I haven't had any luck keeping it from leaking unless I let it set up overnight before I fill it up.

Tx Firefighter · 08-12-2013, 09:35 PM

A new FelPro cover gasket is cheaper than a tube of silicone. It's also quicker and looks more sanitary than silicone does.
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**Stocker** · 08-13-2013, 01:33 AM

If you decide to use silicone anyway..... use this stuff, it's made for gear oil.

Siedl · 03-10-2020, 05:03 PM

Quote:

Originally Posted by cdowns

i use royal purple 2quarts for a 12bolt rear// no drain plugs on a 12bolt/ no additives required with royal purple or most synthetic gear oils nowadays

check the bolt holes of the cover and make sure they are flat overtightening causes them to "bell" out and cause poor sealing and leaks

How do you drain/fill with no drain holes? I have a 12 bolt diff and I’m pretty sure it’s what’s making that horrible clacking sound...found a small bend at the bottom of the diff where the fluid is slowly seeping out.

weq92f · 03-10-2020, 05:29 PM

.
My 8+ inch 12 bolt only held 1 and a quarter quart using a stock stamped cover.

-klb

54blackhornet · 03-10-2020, 06:16 PM

Can anyone suggest a different cover from the stock steel one ? Mine is rusty !

**dmjlambert** · 03-10-2020, 06:50 PM

Hold on to your rusty one, an aftermarket one will not be as good. I took mine off when I drained it to refill with new oil. While it was off I cleaned it up and painted the outside, and stuck the bolts through a piece of cardboard and painted the bolt heads. The inside was very nice with no rust due to being constantly exposed to oil. I used a POR-15 starter kit from Amazon.com, it was quite inexpensive and the whole job just took a couple teaspoons of paint. A little goes a long way with POR15. Do not get POR15 on anything you don't want painted permanently, such as your hands. It will not come off. Make sure the lid and top lip of the paint can are perfectly clean when you re-close the can, or the lid will not come off again the next time you have a little rust-proofing project. Dip into the can with a plastic spoon and transfer the paint to a disposable container such as a pie tin, so you don't contaminate the paint. This gives you an excuse to start the job by eating pie.

72c20customcamper · 03-10-2020, 07:12 PM

Quote:

Originally Posted by Siedl

How do you drain/fill with no drain holes? I have a 12 bolt diff and I’m pretty sure it’s what’s making that horrible clacking sound...found a small bend at the bottom of the diff where the fluid is slowly seeping out.

No drain hole . You drain it by removing the cover the fill is on the front side in the webbing. Just a pipe thread plug . Fill till it starts coming out .

When I replaced the Chevelle 12 bolt with a 9 inch. I had a new fill added and a drain plug drain plug is protected by the fing on the bottom . I added the one picture that looks like its chrome just cause I like it

**Stocker** · 03-10-2020, 07:14 PM

Quote:

Originally Posted by Siedl

How do you drain/fill with no drain holes? I have a 12 bolt diff and I’m pretty sure it’s what’s making that horrible clacking sound...found a small bend at the bottom of the diff where the fluid is slowly seeping out.

You have a fill hole though, right? Remove the cover to drain the diff.

**Steeveedee** · 03-10-2020, 10:28 PM

Quote:

Originally Posted by Siedl

How do you drain/fill with no drain holes? I have a 12 bolt diff and I’m pretty sure it’s what’s making that horrible clacking sound...found a small bend at the bottom of the diff where the fluid is slowly seeping out.

Make sure that you can get the fill plug out before you drain the gear oil! If it is stripped, your truck will be immobilized until you can get it out.

A clacking noise will probably be a u-joint.

Siedl · 03-11-2020, 05:14 AM

Quote:

Originally Posted by Steeveedee

Make sure that you can get the fill plug out before you drain the gear oil! If it is stripped, your truck will be immobilized until you can get it out. But the cover will come off even if the drain plug is still in, won’t it?

A clacking noise will probably be a u-joint.

I think you’re right about that.
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08-03-2011, 05:05 PM	#1
dukcaln Registered User Join Date: Jul 2011 Location: vacaville ca Posts: 1,304	72 differential oil/fill line? what do you all suggest for differential oil and how much do I put in... is there a fill line or something... I am getting ready to go out and take cover off cause it is leaking from bottom (since I bought truck) and re-seal. Then put new oil in..... what do you all suggest, is there a simple way to know when it is full __________________ 04 CHEVY LLY LS DURAMAX 4WD. MODS TO FOLLOW, EFI LIVE, BUILT TRANS, LBZ MP, LIFT PUMP *SOLD* 1972 chevy c10

08-03-2011, 05:12 PM	#2
TobyArnot Quit if it's not FUN!!! Join Date: Jul 2010 Location: Indian Trail, N.C, Posts: 864	Re: 72 differential oil/fill line? Me too!!

08-03-2011, 05:14 PM	#3
bosco200 Registered User Join Date: Dec 2009 Location: Ste. Genevieve, MO Posts: 526	Re: 72 differential oil/fill line? 3-4 quarts, Royal Purple is good stuff

08-03-2011, 05:15 PM	#4
racer57 Registered User Join Date: Jan 2011 Location: Lubbock, Texas Posts: 46	Re: 72 differential oil/fill line? Always been told fill it until rear end oil comes out fill plug. Posted via Mobile Device Posted via Mobile Device

08-03-2011, 05:24 PM	#5
fastwillie 696969 ~Rest In Peace~ Join Date: May 2005 Location: CALIFORNIA NOR CAL Posts: 9,707	Re: 72 differential oil/fill line? remove the drain plug first before poppin the cover off ,basic open diff. 2qts 75-90 w gear oil Quaker state or Lucas lubrication ,take a ball peen hammer and slight tap the bolt holes flat and clean off surface to prep for silicone gasket sealer ,install the cover with the rtv ,tighten the bolts 20 ftlbs ,add oil to the drain hole on the side of the rear just when it drips out put the plug in if its posi used the synthetic oil __________________ is it fast ? it has a lighting bolt donut? B___H please, I can remove 90% of your so called "beauty" with a kleenex

08-03-2011, 05:51 PM	#7
dukcaln Registered User Join Date: Jul 2011 Location: vacaville ca Posts: 1,304	Re: 72 differential oil/fill line? cool thanks..... I don't think it is posi, unless it came that way from factory... I think it is the factory 3.73 __________________ 04 CHEVY LLY LS DURAMAX 4WD. MODS TO FOLLOW, EFI LIVE, BUILT TRANS, LBZ MP, LIFT PUMP *SOLD* 1972 chevy c10

08-04-2011, 11:54 AM	#8
eagleuh1 Registered User Join Date: Jul 2009 Location: Russellville, Arkansas Posts: 1,699	Re: 72 differential oil/fill line? Put the additive in for Posi too if you have a posi. I like to overfill mine a little so it runs out to the axle tube ends. I just force it in after it overflows a little then put the plug in real quick. Jim

08-04-2011, 12:10 PM	#10
dukcaln Registered User Join Date: Jul 2011 Location: vacaville ca Posts: 1,304	Re: 72 differential oil/fill line? thanks guys got it all done.... __________________ 04 CHEVY LLY LS DURAMAX 4WD. MODS TO FOLLOW, EFI LIVE, BUILT TRANS, LBZ MP, LIFT PUMP *SOLD* 1972 chevy c10

08-12-2013, 11:41 AM	#12
craig7070 Registered User Join Date: Jul 2013 Location: Roseville, CA Posts: 167	Re: 72 differential oil/fill line? Do you put the new cover on almost all the way they add oil if you have the 12Bolt? __________________ 1972 C10 Custom Deluxe 2 Owner Project "Lumberjack" 83K Original miles Work in progress....Got the truck for free all original

08-12-2013, 12:05 PM	#13
Bigdav160 Registered User Join Date: Apr 2011 Location: Klein Texas Posts: 3,852	Re: 72 differential oil/fill line? There is fill plug on the pinion side. Takes a 3/8 square drive to remove. Synthetic gear oil in the rear axle is a perfect application. __________________ My Classics: '72 K20 Suburban + '65 Dodge Town Wagon '72 Corvette Roadster +'67 Corvette Roadster '73 Z-28 Camaro '63 Ford SWB Uni Pickup '50 Ford Coupe

08-12-2013, 08:00 PM	#15
NCBowtie Registered User Join Date: Nov 2012 Location: Seagrove, NC Posts: 50	Re: 72 differential oil/fill line? YMMV but I haven't had any luck keeping it from leaking unless I let it set up overnight before I fill it up.

08-12-2013, 09:35 PM	#16
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: 72 differential oil/fill line? A new FelPro cover gasket is cheaper than a tube of silicone. It's also quicker and looks more sanitary than silicone does. Posted via Mobile Device

08-13-2013, 01:33 AM	#17
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,498	Re: 72 differential oil/fill line? If you decide to use silicone anyway..... use this stuff, it's made for gear oil. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

03-10-2020, 05:29 PM	#19
weq92f Registered User Join Date: Oct 2016 Location: Dallas Texas Posts: 2,883	Re: 72 differential oil/fill line? . My 8+ inch 12 bolt only held 1 and a quarter quart using a stock stamped cover. -klb __________________ 67 C10 fleet fuel injected '70 402, 700r4, 3.73 posi 07 335 sport turbo 6sp 94 Trans Am GT LT1 6sp posi -- sold after 22yrs 99 540 sport V8 6sp -- sold 73 240z L24 4sp -- given to friend 68 C10 step 350/350 3.73 open -- sold

03-10-2020, 06:16 PM	#20
54blackhornet Registered User Join Date: Jul 2008 Location: Eastern Oregon Posts: 2,262	Re: 72 differential oil/fill line? Can anyone suggest a different cover from the stock steel one ? Mine is rusty ! __________________ 71 C-20 07 Magnum RT AWD



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03-10-2020, 06:50 PM	#21
dmjlambert Senior Member Join Date: Apr 2016 Location: Cypress, TX Posts: 3,573	Re: 72 differential oil/fill line? Hold on to your rusty one, an aftermarket one will not be as good. I took mine off when I drained it to refill with new oil. While it was off I cleaned it up and painted the outside, and stuck the bolts through a piece of cardboard and painted the bolt heads. The inside was very nice with no rust due to being constantly exposed to oil. I used a POR-15 starter kit from Amazon.com, it was quite inexpensive and the whole job just took a couple teaspoons of paint. A little goes a long way with POR15. Do not get POR15 on anything you don't want painted permanently, such as your hands. It will not come off. Make sure the lid and top lip of the paint can are perfectly clean when you re-close the can, or the lid will not come off again the next time you have a little rust-proofing project. Dip into the can with a plastic spoon and transfer the paint to a disposable container such as a pie tin, so you don't contaminate the paint. This gives you an excuse to start the job by eating pie. Last edited by dmjlambert; 03-10-2020 at 07:05 PM.

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