I went to change my 2009 manual trans and diff oil this weekend, only to find the drain plug on the diff to be covered by the rear leaf spring. There is only about enough space to get my finger in there to touch it, so im not sure what tool i can use to get at it, a socket definitely wont work.

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Also, i noticed when i opened the fill plug on the TRANS first, a significant amount poured out the top (car was perfectly flat). I was able to fill the trans with just shy of 3.5qts. I looked through all the threads i could find prior, and saw nothing about running the car before topping off the trans (even with the trans cooler on the Z51). So is that necessary, or is what i did correct? (shifts feel better, and no noise)

Thanks for any/all advice!

 

Check out this post. Sounds like you need an "L" shape allen wrench.

http://www.theredlion.us/C6%20Differ...luid%20DIY.pdf

 

Not to be funny but are you sure it's an '09? Only the '05's were supposed to have that problem.

Anyway, take a look at these 2 for ideas used on '05's:

http://forums.corvetteforum.com/1584015445-post11.html

http://forums.corvetteforum.com/c6-t...rain-plug.html

 

I appreciate the quick response, but this is the thread I used as reference, and you can see by the pics that the diffs are different and I don't have as much clearance as the 2005 model did. My roommates 07 Z51 drain plug is well clear of the spring, yet my 09 is above it. This goes against what I have read because I thought the newer ones fixed this.

 

Haha, I know right?! This makes no sense, I have an 09 cyber grey metallic (color came out in 09 ;-) )

 

I have the same problem with my 09 non-Z51. there is simply no space to squeeze anything in there to get that plug out.

 

I just changed my fluid this past weekend, and I was stymied for a while until I looked in the service manual. The manual calls the round socket head plug a drain plug, but it also calls the horizontal hex head plug above it a drain plug also.
I wrapped some foil around the leaf spring, removed the plug and let it flow. The hex head plug has a reusable o-ring as a seal instead of the plastic washer used on the other plugs.
After reading a few threads on how bad the peoples gear oil looked, I decided to change it along with the engine oil. My oil with 27,000 miles on it looked like it could go much longer, it was still clear with a blonde / brown tint to it.

 

Very interesting, I was wondering if that was also a drain plug, but was worried it was part of the case or a mounting bolt, so I let it be. If this is the case, things got way easier! I will definitely talk to my vette mechanic at the dealer and verify since I don't have a manual yet.

Thanks!!

 

What I do not understand is why some plugs are over the spring while others are not or why some apparently do not have the second drain plug.
FYI my car is an 09 w/ Z51, and MZ6.
Perhaps the plug location varies with auto and manual trans or maybe gear ratio.

 

You didn't ask for this response but why in the heck are you changing the diff and trans fluid in a 09. You are wasting money and time IMHO.

That said if you are intent on doing it, on my c5 diff equipped car which has the same problem as yours, I had to get at my diff drain. I removed he 4 mounting bolts from the spring and used a long pry bar to pull the leaf down enough to get an Allen wrench on it.

BTW I have followed the DIC oil change recommendations and it usually goes about 9000 miles. I've had the oil analyzed by Blackstone and they said I still had plenty of additive left, go for 10,000 miles next time.

I am not a big fan of throwing away perfectly good fluids.

 

One thing that may help is to take the bow out of the spring. That can be done by lowering the rear wheels onto blocks on the ground so that the weight of the rear of the car is back on the rear wheels. I never had the diff drain plug blocked by the spring on the 06Z, 07 F55 or 08 F55 cars.

 

I agree with Joe; I changed my gear oil because of a couple threads I had read here, talking about how bad their oil was after only a short period of time.

In reality, the gear oil was fine, It was the best looking oil I ever changed!
I would say that unless you track your car, the oil in these diffs should last a very long time.

 

You make some good points but I respectfully disagree with the statement in bold.

With any vehicle, preventative maintenance is never a bad thing. More specifically to this topic, Corvettes chew up diff fluid pretty quick. Depending on the OP's mileage, some fluid services are definitely in order. You never know, I had a 2010 C6 leave my shop not too long ago with 95K on it already.

FWIW, I've drained diff fluid out of cars with 30-40K on them and the fluid looked like Columbian coffee with no creamer.


OP, what I usually do is break loose your rear cradle bolts along with the diff mount bolts. If your car is on jack stands, you can move your jack into position somewhere under the trans and just jack your rear differential up & away from the spring a few inches. This will enable you to get a tool in there to drain your fluid without having to physically remove anything. Just jack her up, then set the diff back down and tighten up your bolts. Done.

Regarding the transmission filling, it is always good practice to fill any transmission using a cooler while the vehicle is running, preferably with the rear wheels in the air running through a gear. This will ensure the cooler is properly filled as well as the transmission case. If you fill the trans "cold", when you fire it up the cooler could suck some fluid down which would result in the case being low. Filling while the car is running and the wheels are turning is the sure fire way to make sure the entire transmission system is completely full.

Good luck.

 

You have a great point, I'm assuming that like most Vettes, an 09 will have few miles.

If he has 100,000 miles, and the service manual recommends changing fluids at 100,000 miles, then proper maintenance is warranted.

However, I see people changing oil at 2000 miles and fluids after a couple of years with low miles - I stand by my comment in that instance that I believe that is wasting money, time and resources.

I have become a fan of spending $35 and getting a Blackstone oil analysis on each of my vehicles every so often (no more than once every couple of years), as I keep my vehicles for a long time (Vette is 7 years, Truck is 16 years, etc.). The analysis tells you what you are dealing with, like they do on aircraft, as you can't really tell from looking. Oil may look dirty but have substantial life left (like all diesel guys know).

 

Me neither, but you never know man. It's ALWAYS a good idea to get OEM fluids out of the car early on IMO. I changed the differential fluid on my '12 GS M6 at 3K miles, and it was like crude oil. I didn't think of it until I opened the first bottle of Dexron LS, and fluid was amber clear . And the better news is the chatter I had at full lock went away. Also replaced the tranny oil, and that one looked fine, but wanted full synthetic in there as well (OEM fluid is not). Also replaced brake fluid, and have been replacing clutch fluid since mile 9 and day 1, since it was dark already (have done it like 20 times).

After getting the original fluids out, with all the break-in crap in them removed, it's okay to go normal intervals then. If differential fluid drains clear, it means it was replaced before IMO... at least in my experience .

 

"Josh@SpartanLSX" Prevention is never a waste of money. Personally, I would rather spend the money on new 100% synthetic oil then on an oil test.

Op, do you have an shorten allen wrench?

On my '05, I use a combination wrench with an shorten allen. Its slow but sure.

 

Ratcheting box end is perfect for this job.

 

Could you please post a pic of this page referring to the second drain plug? I contacted my vette technician at the dealer and he said there is no such secondary drain plug on any of the diffs. I am inclined to believe you though, having seen this hex bolt location, and no other diff has anything similar in that area. I just would like some evidence before i go removing random bolts.

Thanks!

 

See Post #7. Apparently the fluid was drained successfully from the hex head bolt as well making it a lot easier for you. I have never seen such a thing on my cars but maybe GM added it to the Z51 Diffs because of the spring location.

 

The two plugs shown in the picture appear to be the same in terms of the amount of fluid that they will drain...the only difference is that one is horizontal and one is vertical.
My '07 has only the vertical plug and it is well aft of the spring. The horizontal plug is simply not there. The fill plug is many inches higher, not right next to the drain plug.