Diff fluid change advice
Thread Starter
Racer
Joined: Sep 2012
Posts: 259
Likes: 6
Diff fluid change advice
I'm planning to change my diff fluid and I was wondering what works best to suck out the old fluid? Also I have read that some folks are using some kind of solvent to pour in and let sit for awhile then suck that out and then add the new fluid. If thats really a good idea then what kind of solvent and how long should it be in there? Also what is the best fluid to use and should I get synthetic or not and should I use the additive with the fluid. Any help is always appreciated.
Thank you
Johnny Y
Thank you
Johnny Y
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
Before you try to suck it out, drive it around for awhile, so the fluid will get warm and thinner. If you use regular gear lube, add the bottle of Posi-Trac additive. If you use synthetic gear lube...I don't really know, but I suspect that you still need the additive.
Burning Brakes
Joined: Sep 2005
Posts: 1,050
Likes: 205
From: Lewes Delaware
When I changed the fluid in my 73, I used a turkey baster attached to a 3' length of clear vinyl hose (lowes or Home Depot). Took about 45 minutes to suck all the fluid out. I did not add any solvent - just drove it to warm up the fluid beforehand.
Fran
Fran
Drifting
Joined: Aug 2005
Posts: 1,372
Likes: 4
From: Springfield VA
They have hand pumps cheap at harborfreight I use that work great for this at less than $10, somestimes $5 onsale/coupon.
http://www.harborfreight.com/multi-u...ump-66418.html
http://www.harborfreight.com/multi-u...ump-66418.html
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Racer
Joined: Aug 2013
Posts: 264
Likes: 58
From: Virginia
I got an oil extractor from harborfreight about 5 or 6 years ago that works great for jobs like this. And you can suck the engine oil out thru the dipstick of most cars, makes for fast oil changes. I use for it everything- 5 cars, snowblower, tractor, lawn mower, wood chipper, etc.
BUT, it doesnt work on my '02 Dodge truck. And I haven't tried it with my 'vette yet.
http://www.harborfreight.com/6-1-4-q...tor-46149.html
BUT, it doesnt work on my '02 Dodge truck. And I haven't tried it with my 'vette yet.
http://www.harborfreight.com/6-1-4-q...tor-46149.html
Burning Brakes
Joined: Mar 2010
Posts: 987
Likes: 7
From: Surrey British Columbia
When I had my differential rebuilt I asked the shop to drill and tap the case for a drain plug. They strongly suggested that I not do that. They claimed that it would weaken the aluminum case. Well, they do nothing but rear ends so I took their advice. Looks like I'll be a "sucker" for the life of this car. 
Le Mans Master
Joined: Mar 2001
Posts: 5,738
Likes: 644
From: Lincoln, CA
LOL I dropped the diff to take the cover off. There was what I'd call slug build up that would not have have come out with just a fluid swap. I used a rag and some brake cleaner to get all the fluid and gunk out.
Over kill yes but I felt better
Over kill yes but I felt better
Racer
Joined: Oct 2001
Posts: 274
Likes: 2
From: Pampa Tx
No matter how you remove the fluid and whichever fluid you use, be sure to put in GM positrac additive. Synthetic alone isn't enough. When I bought my '72, it had set long enough that the clutches would bind up when the rearend was warm and turning corners. I never got it to really work right until I went back to GM fluid differential lube and additive. I tried cleaning and several fluid changes and doing lots of circles in the parking lots prior to going back with the GM lubes. That has been 12 years ago and it still performs well.
Pro
Joined: Feb 2000
Posts: 741
Likes: 46
From: Hebron IN
Get one of those small pumps you attach to your electric drill. Any hardware or big box store will have them for around $10 bucks.
One hand to operate the drill and the other to keep the intake hose pushed to the bottom of the diff. The fluid will be out in less than 2 minutes. The gear lube bottles have a cone shaped spout, put a hose on it and refill. It would take a really special kind of person to make a mess out of such an easy maintenance job.
The Harbor Freight hand pump mentioned above also works well but is a little more time consuming.
One hand to operate the drill and the other to keep the intake hose pushed to the bottom of the diff. The fluid will be out in less than 2 minutes. The gear lube bottles have a cone shaped spout, put a hose on it and refill. It would take a really special kind of person to make a mess out of such an easy maintenance job.
The Harbor Freight hand pump mentioned above also works well but is a little more time consuming.
Safety Car
Joined: Jun 2004
Posts: 4,652
Likes: 80
From: Lakeland Florida
I used a hand pump, or a suction pump, to remove all of the fluid.
One thing that made this easier was to remove the spare tire housing.
Then you have more room to maneuver around.
The advice someone told me to do next was to put in the additive first. That makes sense. Since once you fill the diff with fluid, then you cannot add any more fluid to it, like the additive. So pour that in first, then fill the diff with fluid unitl it starts to leak out of the hole.
kdf
One thing that made this easier was to remove the spare tire housing.
Then you have more room to maneuver around.
The advice someone told me to do next was to put in the additive first. That makes sense. Since once you fill the diff with fluid, then you cannot add any more fluid to it, like the additive. So pour that in first, then fill the diff with fluid unitl it starts to leak out of the hole.
kdf
Burning Brakes
Joined: Apr 2013
Posts: 926
Likes: 2
From: Castle Rock CO
I replaced mine just a few months ago after buying a 1977. I used Mobil One 75-90 LS full syn and like others suggested a Limited Slip Additive. While I did not use the GM additive I chose the most expensive on the Store Shelf at the Local Parts Store. My Fuild was Dark Gray when I sucked it out and any transfer pump will work.
Purchase 2 Quarts of the Diff oil and 4 ounces of additive. You will only be able to pull about 1.5 quarts out of the diff and not completly drain it since there is no drain plug.
I had to drop my entire spare tire carrier to get the plug loose and could not get it loose any other way. It was rusted in after 35 years. Once removed the first time it is easier if you go to do it again.
I will drain mine again next spring and refill it again since I could only pull 1.5 quarts out of the 2 Quart Diff. I want the fluild as fresh as possible and probably never need to change it again. Diff Fluild should be replaced about every 30,000 to 50,000 miles in all my reading.
Purchase 2 Quarts of the Diff oil and 4 ounces of additive. You will only be able to pull about 1.5 quarts out of the diff and not completly drain it since there is no drain plug.
I had to drop my entire spare tire carrier to get the plug loose and could not get it loose any other way. It was rusted in after 35 years. Once removed the first time it is easier if you go to do it again.
I will drain mine again next spring and refill it again since I could only pull 1.5 quarts out of the 2 Quart Diff. I want the fluild as fresh as possible and probably never need to change it again. Diff Fluild should be replaced about every 30,000 to 50,000 miles in all my reading.
Last edited by MakoJoe; Sep 4, 2013 at 12:26 AM.
Instructor
Joined: Apr 2009
Posts: 124
Likes: 4
From: Phoenix, Az
Pro
Joined: Feb 2000
Posts: 741
Likes: 46
From: Hebron IN
You can get them with molded barbed ends or threaded garden hose ends. I like the threaded ends and just use a narrow washing machine hose cut in half.
Advanced
Joined: Jul 2013
Posts: 86
Likes: 0
From: Yukon OK
Here's 2 pumps. I used this first one. It took about 5 minutes to get the warm fluid out.
http://www.walmart.com/ip/Custom-Acc...-Pump/16767856
http://www.walmart.com/ip/Mercury-Qu...-Pump/17165291
http://www.walmart.com/ip/Custom-Acc...-Pump/16767856
http://www.walmart.com/ip/Mercury-Qu...-Pump/17165291
