71 Posi Drain

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Oct 24, 2009 | 05:08 PM

71 Custom

Thread Starter

Heel & Toe

Joined: Jul 2009

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71 Posi Drain

I have a 71 and tried to drain the fluid in the rear. got a suction pump not to successful. I know about using the additive as i have some chatter. I read some one said you can add a drain.
Can anyone give me any particulars and possibly the best place to locate it.

This unbelievable forum has saved me countless hours and saved me hours troublingshooting problems

Oct 24, 2009 | 06:31 PM

dmayhew

Drifting

Joined: Oct 2007

Posts: 1,254

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From: Brown Summit North Carolina

For this 1st time , you will have to remove the rear cover to fully drain the old fluid. That is a job since it is attached to the rear cross member.

You can buy a kit from any of the Corvette parts houses that has a templete to mark and drill a hole in the bottom of the hsg. fto install a drain plug for future use. The catch is a 71 is driven so few miles (typically) that the new easy to use drain may never be used.

Once you refill the unit you will also add 1 bottlr of additive.

I would uses GM fluid and additive. @ bottles of fluid and the 1 additive.

Thanks
David

Last edited by dmayhew; Oct 24, 2009 at 09:37 PM.

Oct 24, 2009 | 08:33 PM

7T1vette

Team Owner

Joined: Jan 2006

Posts: 37,637

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From: Crossville TN

What problem are you having when trying to suction the diffy fluid? Did you 'prime' the suction device first? I just did this with a cheap bulb-squeeze type siphon..but you have to fill the bulb/line with fluid first to get it to function effectively. With such thick fluid, you also have to wait for the squeezed bulb to draw the fluid into it. It works better if you have run the car to warm the fluid first.

Oct 24, 2009 | 10:50 PM

71 Custom

Thread Starter

Heel & Toe

Joined: Jul 2009

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I bought a suction gun from NAPA. It is bascislly a grease gun bottom cyclinder with the plunger and a plastic hose. Put the hose in the fill hole and pulled out only about a ounce of green sludge looking stuff. The car has been sitting for over 20 years but the posi was rebuilt and only has about 10 K on the car bfore it sat on blocks in storage. Should I suck up some regular oil to prime the gun. Never thought about having to prime it. Dont really want to tap a drain but just couldn"t suck the oil out. If I can manage to get the oil out and I will get a turkey baster if need be. Is their anything that can be put into the rear to flush it out ??

Oct 25, 2009 | 11:51 AM

7T1vette

Team Owner

Joined: Jan 2006

Posts: 37,637

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From: Crossville TN

If the posi grease has caked-up, you may have to put some mineral spirits or other [petroleum] solvent in the 'pumpkin' to thin it out before suctioning. If the car is operational, you could put some lighter weight oil in it and run it a while to thin the old 'goo' and warm it up. Keep the car at low speeds and don't use much throttle. It could be that the lube is almost dried up and there is little of it left. You can always fill it with some inexpensive oil just to see how much it takes. The rear end should take a bit less than 2 quarts of differential lube. If you can get more than a quart of oil in it, there's very little left.

Then you can make use of that suction gizmo to remove the 'scrap' oil before filling it with the good stuff and a tube of posi-trac additive.

Oct 25, 2009 | 12:19 PM

71 Custom

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Heel & Toe

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Thanks I will give it a try

Oct 25, 2009 | 12:22 PM

71 Custom

Thread Starter

Heel & Toe

Joined: Jul 2009

Posts: 16

Likes: 0

Do you the best spot to tap a drain which might need to be done if it truly has dried up. Certainly will be easier to flush it out. Someone said you can find the template and stuff needed but I have searched on the internet and found nothing.

Oct 25, 2009 | 12:51 PM

Mike Ward

Race Director

Joined: Jul 2001

Posts: 15,892

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Quote:

Originally Posted by 71 Custom

Those drain holes are a bad solution to a non existent problem. If you are convinced that the old oil is caked and cannot be suctioned out, a drain hole won't help either.

If this is truly the case, take the diff out and clean it properly. My guess it that you have a sh*tty pump and cold oil.