Anyone know the hex plug sizes for the MN6 trans oil drain/fill plugs as awell as differential plugs?

Looking at them the diff plugs appear more difficult to access. Has anyone had a problem getting a hex key on these? Is loosening them tough from the factory?

 

Tansmission drain plug torgue (Size 3/8" square drive) 20 lb ft
Transmission fill plug torque (Size 3/8" square drive) 20 lb ft

 

No problems here. The diff plugs use a 10mm

 

Which fluids are you going to replace them with? Brands? Synthetic or non synthetic?

 

I don't know yet. I am inclined to use Mobil 1 synthetic trans fluid and Mobil 1 75-90 synthetic gear oil for diff. I can't yet determine if I need a limited slip additive as well for diff if using synthetic oil. Any advice?

With all the fuss over Redline fluids and Amsoil, I don't know what is best.

 

They are all good. Use what you feel comfortable with. If it matters, I've been using the AMSOIL Severe Gear Extreme Pressure Synthetic 75w90 in my C5 Z06 diff for years on the track and haven't had any problems, though I did have my diff rebuilt this winter as a precaution after loosing the left axle seal in my last race last year. This fluid comes with friction modifier in it and I've never needed any additional modifier in my car.

 

Same thing here but the factory fill for the transmission fluid is not synthetic just regular ATF DEXRON III (H) or now DEXRON IV. Most of these synthetics say friction modifier already added and not needed.

 

Check the manufacturer's label to see what is recommended. If you decide to use Mobile One synthetic gear oil in the differential, most owners making the change would add one bottle (4 oz?) of GM's limited slip additive.

Some have added two bottles to insure they eliminated a stubborn problem, but that's generally overkill. IMO, the lubricity of synthetic lubricants is not enough different from mineral oil lubricants to allow you to skip the additive. If you don't need the additive, putting it in anyway generally won't do any harm.

On the other hand, if any distributor's bottle says use of limited slip additive is NOT REQUIRED with their product, I would not use limited slip additive. It's probably not required because the additive has already been mixed into the product, not because their synthetic lubricant alone is so "slick" it doesn't need it.

 

That is Red Line you don't need to add anything extra.
Amsoil says you can add their extra friction modifier but how do you know if you need it without filling it up first? I mean you want to do this all in one shot not going back and forth draining and changing a few times and listening for clunking or whatever noises. So you might as well add the extra friction modifier if you use Amsoil.

 

Not correct. The AMSOIL Severe Gear 75w90 comes with the friction modifier pre-mixed in just like Redline 75w90. I've been running this fluid in my C5 Z06 diff on the track for several years now without any chatter.

Note that Redline makes a 75w90 for diff without limited slip clutch plates called 75w90NS. This diff fluid would need the 4 oz of additive as it doesn't come with any.

 

I remember reading that Amsoil has extra friction modifier to add if needed.
Don't know now if I want to perform that rear differential change of fluid to get any metal shavings out at 11,100+ miles as I hear about more rear end noise problems on the C-6 which I haven't had that problem "If it ain't broke don't fix it". I read some TSB I believe that if it is a first time fix that dealer will change fluid. If a second time fix after first time when fluid was changed then they replace the rear end inside

 

They do but it was really designed for use with other fluids, not AMSOIL gear lubes: AMSOIL Slip-Lock Differential Additive

Here is a quote off the AMSOIL corporate literature for this product:
"NOTE: AMSOIL Synthetic Gear Lubes do not require the use of this additive. However, not all differentials respond the same and if chatter is noticed, the addition of AMSOIL Slip-Lock will eliminate it. For chattering differentials not running AMSOIL Gear Lube, this product is an excellent solution to the problem."

 

I changed mine with Royal Purple Max-Gear and Synco-Max.

 

11K MILES!!! What the...? Awwww, man, it's TOO LATE NOW!

If you were going to do this fluid change as preventative maintenance, you should have done it at 3K! I'm pretty sure your ring gear and pinion have already been pitted and scored by all those metal shavings floating around in there, and your A4 is sloughing off clutch disc material like a shedding snake. Listen carefully when you drive...I'll bet it's already making noise...it'll sound like a low moan that increases in frequency with speed. It'll probably fail at about 36 months and one week, or 36500 miles, "whichever comes first".

Only kidding. LS WON, in spite of what **** Corvette owners do about maintenance, I would bet $100 that 95% of all cars in the junk yard still have their original factory fill in the differential and transmission. It's usually collisions that put cars in the junk yard; not the poor maintenance practices people follow. Just follow what the General says to do for maintenance, and use the approved fluids they recommend, and your car will outlast you.

 

Yes I was going to do the rear end differential and auto A-4 trans fluid change as preventative maintenance but at 3,000??
Actually I would have done rear end differential and auto trans right after 1,000 miles when I did the engine oil change for metal shavings but had never heard of doing the rear end or auto trans for this like the engine oil at 1,000. So now I'm at 11,100+ miles. My dealership recommends to do the Transmission service at 25,000 miles and do the rear end service at anytime.

So then you would suggest following the General's orders??
I have the manual right in front of me.
If I were to do that then the rear end 75W/90 synthetic fluid never needs to be changed unless it leaks.
The A-4 auto trans use ONLY DEXRON III (H) or now DEXRON IV which replaced DEXRON III (H) which I believe is an ATF fluid and not a synthetic fluid which means I can't use a synthetic fluid in the auto trans?
It says in the manual to change the Automatic transmision fluid and filter every 50,000 miles for severe service or 100,000 miles if not severe service.
I have never known anything else but severe service since wherever you go there is heavy traffic and end up idling in that all the time.

"Notice: Use of automatic transmission fluid labeled other than DEXRON-III, Approved for the H-Specification, may damage your vehicle, and the damages may not be covered by your warranty. Always use automatic transmission fluid labeled DEXRON-III, Approved for the H-Specification".

This means I can't use a synthetic Fluid in the automatic A-4 Transmission *****:
I'm so
I can't handle this new technology

 

Your dealership's recommendation to change ATF at 25K is primarily for their benefit ($$), not yours...It has ABSOLUTELY NO BASIS in good maintenance unless you race your car every weekend. If the owner manual says 100K miles, why would you consider doing it at 25K?

Quit fretting about not being able to throw your money down a synthetic oil rathole...by the time you put on 100K miles, they'll probably be using synthetic Dexron XII. Happy Motoring.

 

Your point is valid as the manual says for severe service 50,000 miles change auto trans fluid and filter as this is on the A-4 trans. It's 100,000 miles for light service or whatever you want to call it but again I don't go by that schedule.
I go by severe service schedule because of the prolonged idling in traffic jams and stop and go driving.
For the rear end it doesn't say anything about changing it in the owners manual other than if it leaks. Dealership told me I can change rear differential fluid at any time.

 

But hey what do you do about all of those metal shavings in auto trans and rear end differential???

 

Seek therapy to help you accept the metal shavings and live with them.

 

Too hard to accept when I know something can be done about it unless having shavings in those components doesn't do any harm?
Also knowing I am putting in better lubricants to protect ring & pinion gears and auto transmission is comforting over what is in there now which would also be dirty too.