Jmccreary

Is there a drain plug on the 1980 differential housing, or do you have to use a pump to remove the old fluid?


Thanks
J

Ben Taylor

You have to pump it out through the fill plug. It took about an hour to siphon the old stuff out of my 81 because it was so thick.

Jmccreary

So would it be better to remove the differential cover to drain or is that a difficult job? Wouldn't using a pump leave some off the old fluid, or is that OK.

Thanks
J

Ryan77

I just changed my tranny and diff fluid this past winter, the siphon from the auto parts store sucked, so I borrowed a good one from a mechanic I know. You can also take off the cover, you'll just need a new gasket for when you put it back on, I'm not sure how hard it is since I've never done that :cheers:

Stewart's74

You cannot remove the diff cover w/o dropping the entire rear end and removing the spring.
Use a hand pump or your wifes turkey baster attached to some hose.
Or go to GM dealer, buy the Gear oil and the bottle of posi additive and go to a quick lube place. Have them suck out the old stuff and put in your GM fluids.

Ben Taylor

The 80-82 vette differential doesn't have a cover like most other GM differentials. The part that would be considered the cover is the same piece that is bolted to the frame. It's easier to remove the whole thing than to try and take it apart while it's in the car.

Jmccreary

I just had an Idea. What if I take a 5 gal sealed gas container and attach 1/2 inch hose to it and the other end into the fill port of the differential, then attach another 1/4 vacuum hose to the container and attach it to the main manifold vacuum port of the car. Start the car and the fluid should evacuate the differential housing and partially fill the 5 gal container. When done disconnect the hoses and the used fluid can be taken to the appropriate recycler. Am I crazy, or do you think this will work?

Or use a shop vac to apply negative pressure to container. Might be a better idea.

J

adamdinat

Shop vac and a plastic can
:thumbs:


I like this idea.

Sure beats a turkey baster :yesnod:

JB

Do what Stewart suggests and let the quickie lube guys do it. It's cheap (cost me $18), and it's a hell of lot easier job with a lift or a pit. And you don't have to deal with the old fluid (it really stinks) or worry about burning yourself on a hot exhaust (you want the car up to temp or the old diff fluid is like molasses and very hard to suck out).

JB

Jmccreary

I think that I am going to take the advice and have the local oil change shop take care of this task. My question now is, is there a special type of oil that I need to get and have them put in, or is it ok to use the oil and addative that they supply. They also offer synthetic oil, it that better? I have read that synthetic oil runs hotter and does not work as well as the conventional oil.

Thanks
J

spikezz4

Call the Corvette Clinic in Sanford FL (407-323-7804) and request a C3 Differential Drain Plub kit. (About $50) It has everything you need to install a drain plug. After the initial installation and draining, it's like an oil change thereafter.

The shop uses synthetic oil in the rear diff. Reduces friction and heat.
Spike

Stoge

I have 2 quarts of the GM lube and 2 bottles of the GM Posi additive. Is this enough? What is the capacity of the diff???

Jmccreary

Well I took the '80 to the local Valvoline oil change shop yesterday to get the fluid changed. For new fluid and the posi additive they charged $25. The guy gave me a big discount because he loves Corvettes. That is the good news.

The bad news is when I got home I noticed that there was a small puddle of fluid under the rearend. I was hoping that it was residual fluid that was sitting on the head shield. So I took it for a drive and parked it, left it sit all night and this morning there are 3 quarter sized oil spots under the differential. I am thinking that fluid must be leaking out of the side seals.

The question is can the seals be replace without taking the rearend completely out of the car? If so, do I just remove the half shafts, replace the seals and reinstall the halfshafts? I was planning on rebuilding the front and rear suspention this winter, but was not ready to get started just yet. Also is there a good source for getting a stock rebuild kit for the rearend? I have seen some kits, but each vendor seems to include a different set of parts. I think I mostly need the soft parts such a bushings.

Thanks
J

JB

I've never done it, but my recollection is that no, they cannot. You have to pull the pumpkin.

However, I'd make darn sure that guy at the quickie lube snugged up the plug first.

JB

Jmccreary

When I get home tonight I am going to get under there and pull the heat shield off and clean everything real good and try to determine where the leak is coming from. The research that I have done today indicates that the rearend would have to be removed from the car to replace the side yoke seals because there are C-clips inside the case that have to be removed to get the yokes out.

The thing did not leak prior to the fluid change, so either it is residual fluid that is sitting on the heat shield, the plug was not tighted to the proper torque or the fluid level is higher now and is leaking out the seals. From the pics I looked at today it seems the fill hole is just at the bottom level of the side seals, so you would think that it would have been leaking this whole time if the seal were bad, unless it had leaked to a level where there was not enought fluid in the case to leak.

Thanks
J

Richard Cooper

Your 80 is the same as my 81, it does not have a cover. I believe its called a rear carrier because it carries the whole rear end. To seperate it you would have to remove the whole rear end and then break it apart. Just go to your local parts store and buy a suction pump. I got one for $ 17.99 and it worked great. Its kind of a pain to get in there, but it can be done. :seeya

Jmccreary

Update: I went home last night and took the spare tire carrier off and the heat shield on the differential off. The heat shield must of had 1 inch of crap on it, so I cleaned it up and wiped everything down. The side and front yoke seals were dry as a bone. I checked the factory assembly manual and found that they call for .001 liters of sealant for the fill plug. I know the quick lube did not put any sealant on the plug, so I took it out and applied some sealant to it. Put everything back together and it appears that there is no leakage. I think what must have been happening it that there might have been a small leak out of the fill plug, and when the quick lube filled the differential all the excess fluid ran down onto the heat shield and saturated the crud that was stuck on it and was slowing leaking off. I am so releived that I do not have to take the rear suspention appart, especially when this is the perfect time of year to be driving the car.


J

Crash80

Amen brother!