got around to changing the fluid in the rear- it seems that it hasnt been changed since it left the factory in 79. having done this for the first time i learned a couple of important things-

1. its a dirty job

2. diff fluid tastes like crap! (dont ask how i found that out)

3. make sure the rear has been warmed up enough our youll pump syrup out of it.

4. those cheapo hand pump things you can buy at wal mart or pep boys do not cut the mustard! took a looong time to pump the old stuff out. kept pumping air most of the time!

5. getting the fluid out was tough, but getting it in is tougher- see #2!

6. warm up the new stuff to get it in easier. i ended up abandoning the hand pump in favor of just refilling the posi additive tube and squirting in the fluid that way.

7. did i mention it was a dirty job?

The drain plug is not as easy to get to as all the photos and descriptions would have you believe. if everything is intact and installed, you have to really reach in there to get it. lucky i found a 12 point socket that fit pretty well and it was not much an effort to get it off. the real hard part was pumping the old gunk out and trying to get the new stuff in- it is just too thick to pump straight out of the bottle. i tried to use another posters advice of setting the new fluid in hot water for a while to get it to flow better, but i guess i did not do it long enough. the plastic squeeze tube for the posi additive worked the best for getting it back in, for lack of anything better to use.

i certainly dont want to have to that for a while! but it was a good thing that i did, because it seemed to have had lost some fluid over the years. i pumped a quart out, but it took easily a quart and a half to fill it.

that might explain the unearthly sounds i was hearing coming from back there.

for all the trouble, i do feel good that i am getting more and more confident to diy rather than go to a mechanic and pay $$ i dont have. it feels good to know i did it myself and that i get to know my car on a more intimate level. guess thats part of  vette ownership.
stevep3162007-01-23 12:40:19

One permanent solution to this (well, half of it, anyway!), which I just implemented recently: drill a drain hole in the bottom of the differential.

I didn't do this without checking first with our very own Dr. Adams. When he gave the procedure his seal of approval, I went ahead and had it drilled and tapped by a local (and highly recommended) mechanic, who suggested it to me in the first place. (This isn't something I could, or would want to try to do, without putting the car up on a lift. So it didn't match your DIY approach, stevep316--but for me, the small amount of $ paid was very well worth it, especially for the 'peace of mind' that it brought).

Just like yours, my diff fluid--what there was left of it, anyway-- was ancient. Now though, I can easily empty it out next time with the car on jackstands. Will still be a bear to refill (although I have a home-made rig with a pump attachment for an electric drill, coupled with plastic hoses, for that task).

Not a drop has leaked since the drilling/tapping--so I'm confident about the integrity of the job.

Man, that would be too cool!

Did you happen to get any pix or stats such as dimensional data for the threads/plug sizes that we could all use?

dnv, a brass 1/8" pipe plug was used, just as Dr. Adams (and the mechanic) ordered. The drill location (verrrry important, as you might surmise!) was shortly ahead of the cover. Sorry, but I don't have photos/exact measurements--but if they'd be helpful to you or anyone else, I'll see about getting some.

The ingenious part of this was to drill a larger diameter hole at first, followed by a smaller drill bit to actually go through the bottom of the differential. That allows the plug to be 'recessed' a little into the case, and provides a little space around the plug for access by a socket or wrench.

Additional tricks of the trade I observed: poke a thin wand tipped with a magnet up into the diff when the hole has been drilled. That way, you not only help to remove any bits of metal produced by the drilling process itself, but you can also clean out any nearby random pieces of metal that might not have flowed out with the old diff fluid. We were both mildly surprised at how much came out with this procedure (not huge or alarming amounts, by any means--but just enough tiny little bits to demonstrate that this is an advised step to take if you decide to do this job).

To state the obvious: great care must be taken to control the drill--you don't want to poke through into any components inside. I monitored the angle of the drill (front/rear, left/right bias) while he operated it. Frequent lubing of the bit helped make it a smooth procedure. Taking it slow is the name of the game.

(Having an attractive, Corvette-lovin' wife standing there trading wisecracks with us as we went didn't hurt either!)

It's a very satisfying sight to see that diff fluid pouring out in a steady stream, just like the oil up front does....

gravity is our friend!

(stevep316, apologies for appearing to have hijacked your thread--didn't intend to...)

Thanks, SFVette.  If you get a chance to shoot a pic of the final product, I would be most appreciative.

10-4 on the Corvette-lovin' wife.  It really helps having one into the hobby almost as much as I am.

stevep316, my apologies also, but a great tip is a great tip, anywhere you get it!

Ecklers, Mid-America, and/or Corvette Central have a kit complete with the template, drill bit, and plug to install the drain plug.
Scott
ranger32007-01-23 15:55:15

[QUOTE=ranger3] Ecklers, Mid-America, and/or Corvette Central have a kit complete with the template, drill bit, and plug to install the drain plug.
Scott
[/QUOTE]

is this in a rebuild kit as i went to all three sites and could not locate anything to add a drain plug?

[QUOTE=SFVette]dnv, a brass 1/8" pipe plug was used, just as Dr. Adams (and the mechanic) ordered. The drill location (verrrry important, as you might surmise!) was shortly ahead of the cover. Sorry, but I don't have photos/exact measurements--but if they'd be helpful to you or anyone else, I'll see about getting some.[/QUOTE]

would really like to see the pics if you can get them.

One of the Gold or Life members should add this to the tips and tricks section...maybe with a link to the alleged Eckler's, MidAmerica sites!

Never could figure out why a drain plug is not standard issue on a REAR differential.  My 2001 F-150 4X4 doesn't have one on the rear pumpkin either.  BUT THE FRONT DIFFERENTIAL DOES...!!!    Go figure.