diff fluid questions. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jakeblues652 · 12-19-2010, 01:04 AM

so i got paid today

and i'm going to get junk for an oil change tomorrow, and i figured why not the axles while im at it. front and back. how much do i need to fill front and rear? and what is the best weight for the NE? right now, its a steady 10-15 degrees, and it could get down as low as -20. about 70-80 average in the summer with the occasional 95+. i dont think it matters with gear oil, but just in case. what do you guys think?

**Stocker** · 12-19-2010, 01:51 AM

Synthetic 75W-90 will do the job just fine. I'm using Mobil-1 but other brands should work as well. Not sure of the amount... a search might turn something up if nobody chimes in.

67chevy1series · 12-19-2010, 02:05 AM

i used chevron or vavoline i think not sure been a while but it was one of those

jakeblues652 · 12-19-2010, 02:38 AM

i dont think it should matter too much, but id honestly be suprised if it was changed once since new, and i think she earned it over the years.

72shortbed12 · 12-19-2010, 03:28 AM

I usually just run 80w 90 but have put 75 in the front. Synthetics are good but I don't know that they re needed unless your doing heavy towing or racing. I'd run dino oil on a daily driver. I just changed mine on my 72 K10 and gears look new even though the oil looked original.

Notrodder · 12-19-2010, 03:35 AM

According to the Haynes manual, 90 weight GL-5. 80 GL-5 for Canada because of the stinkin' cold (you decide). The capacity is between 4-6 pints per axle depending on which axles you are running. 7.2 if it's a 10 1/2 dana, but I would expect that to be 3/4 ton at least.

So, 1 - 1 1/2 gallons for the axles - posi additive if needed. If you have a manual transmission, you could change that out with another 3.5 pints for a 3-speed or 7 pints for a 4-speed. Transfer case would be 5 pints unless it's full time (8.25 pts.).

I like to get the stuff by the gallon with the pump dispenser, because it is clean and easy to use.

I've read somewhere that you should change the stuff periodically even if (especially if) it is unused because of an acid that forms in it.

RustyParts · 12-19-2010, 09:36 AM

Special oil for Posi units.

cdowns · 12-19-2010, 10:29 AM

lots of synthetics require no special additives for posi rearends// irun synthetic in everything ii've owned for the past 15years even wheel bearing grease i use synthrtic

12-19-2010, 01:51 AM	#2
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,728	Re: diff fluid questions. Synthetic 75W-90 will do the job just fine. I'm using Mobil-1 but other brands should work as well. Not sure of the amount... a search might turn something up if nobody chimes in. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

12-19-2010, 02:05 AM	#3
67chevy1series Registered User Join Date: Mar 2010 Location: a t w a t e r cali 95301 Posts: 10,713	Re: diff fluid questions. i used chevron or vavoline i think not sure been a while but it was one of those

12-19-2010, 03:28 AM	#5
72shortbed12 Registered User Join Date: Feb 2010 Location: Santa Clara Utah Posts: 85	Re: diff fluid questions. I usually just run 80w 90 but have put 75 in the front. Synthetics are good but I don't know that they re needed unless your doing heavy towing or racing. I'd run dino oil on a daily driver. I just changed mine on my 72 K10 and gears look new even though the oil looked original. __________________ 1972 K10 4wd Swb 350, 4 speed, 205 t-case Sold 1971 Cheyenne 2wd Lwb 350 4 speed Sold 1972 K5 blazer 4WD auto A/C

12-19-2010, 03:35 AM	#6
Notrodder Registered User Join Date: Jun 2010 Location: Lompoc, CA Posts: 104	Re: diff fluid questions. According to the Haynes manual, 90 weight GL-5. 80 GL-5 for Canada because of the stinkin' cold (you decide). The capacity is between 4-6 pints per axle depending on which axles you are running. 7.2 if it's a 10 1/2 dana, but I would expect that to be 3/4 ton at least. So, 1 - 1 1/2 gallons for the axles - posi additive if needed. If you have a manual transmission, you could change that out with another 3.5 pints for a 3-speed or 7 pints for a 4-speed. Transfer case would be 5 pints unless it's full time (8.25 pts.). I like to get the stuff by the gallon with the pump dispenser, because it is clean and easy to use. I've read somewhere that you should change the stuff periodically even if (especially if) it is unused because of an acid that forms in it.

12-19-2010, 09:36 AM	#7
RustyParts Registered User Join Date: May 2006 Location: Wyman, Kentucky Posts: 403	Re: diff fluid questions. Special oil for Posi units. __________________ 1972 GMC Jimmy, 4WD, 454 CI, 350 Turbo, 4" lift, 35" tires The math teacher said my son "Bubba" could be a mathmatical genius. cause he's got 13 fingers!

12-19-2010, 10:29 AM	#8
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: diff fluid questions. lots of synthetics require no special additives for posi rearends// irun synthetic in everything ii've owned for the past 15years even wheel bearing grease i use synthrtic __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY



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