Differential questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

RicksTrucks · 08-25-2005, 12:41 AM

I need to find out what ratios my trucks are. Several have said to take the cover off and count. And change the oil while you are at it. So:

1. If I just take the cover off, will enough of the old drain out or do I need to raise the front-end some? Or pump it out?

2. I know I will need to put on a new gasket. Do these need gasket stuff and if so, what type? High heat?

3. Any particular brand of oil best. Saw some at O'reilys, but don't remember the brand - may have been their own.

4. Any thing else I should do while I have it open?

I know there are several FAQs about how to determine ratio and I will find those.

Fred T · 08-25-2005, 05:48 AM

Usually you can find the ratio stamped on the ring gear. I've seen some on the outer edge, some on the machined surface in the center. To drain the oil you can remove the bottom cover bolts, oil will flow out the holes, but not real fast. It's the cleanest way. You can also loosen the cover bolts and pry the cover loose, the oil will come running out the bottom. For these older trucks any of the 80W-90 lubes work, I usually buy the lower cost house brand.

For gasket sealing, I've had my best results with Permatex #3. You will need to seal the bolts, too.

70short/step · 08-25-2005, 07:33 AM

If it is a posi, make sure you add the additive when you replace the gear lube!

Longhorn Man · 08-25-2005, 05:27 PM

I have never bothered with a gasket in my life...just sealant. If you want the best kind, The Right Stuff is recomended by all the OEMs and is awsome stuff. It is also kinda expensive.
As far as brand... go with what you want. However, I will say that synthetic is the best thing you can do. Again, expensive...but good stuff.

08-25-2005, 12:41 AM	#1
RicksTrucks Senior Member Join Date: Jan 2005 Location: Claremore, OK 74017 Posts: 2,640	Differential questions I need to find out what ratios my trucks are. Several have said to take the cover off and count. And change the oil while you are at it. So: 1. If I just take the cover off, will enough of the old drain out or do I need to raise the front-end some? Or pump it out? 2. I know I will need to put on a new gasket. Do these need gasket stuff and if so, what type? High heat? 3. Any particular brand of oil best. Saw some at O'reilys, but don't remember the brand - may have been their own. 4. Any thing else I should do while I have it open? I know there are several FAQs about how to determine ratio and I will find those. __________________ 68 Short Stepside C-10 69 SWB C-10 70 Flatbed C-20 70 LWB C-20 BB402 70 LWB C-10 CST 70 LWB C-10 CST 71 Short Stepside Cheyenne C-10 72 LWB C-10 72 Blazer 4x4 4spd 95 Jeep Cherokee 4x4

08-25-2005, 05:48 AM	#2
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	Usually you can find the ratio stamped on the ring gear. I've seen some on the outer edge, some on the machined surface in the center. To drain the oil you can remove the bottom cover bolts, oil will flow out the holes, but not real fast. It's the cleanest way. You can also loosen the cover bolts and pry the cover loose, the oil will come running out the bottom. For these older trucks any of the 80W-90 lubes work, I usually buy the lower cost house brand. For gasket sealing, I've had my best results with Permatex #3. You will need to seal the bolts, too. __________________ Fred There is no such thing as too much cam...just not enough engine.

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08-25-2005, 07:33 AM	#3
70short/step Registered User Join Date: Dec 2003 Location: Stockton, CA Posts: 1,579	If it is a posi, make sure you add the additive when you replace the gear lube! __________________ For every person with a spark of genius, There are a hundred with ignition trouble. 70 Short/Step

08-25-2005, 05:27 PM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	I have never bothered with a gasket in my life...just sealant. If you want the best kind, The Right Stuff is recomended by all the OEMs and is awsome stuff. It is also kinda expensive. As far as brand... go with what you want. However, I will say that synthetic is the best thing you can do. Again, expensive...but good stuff.



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