2000 c5 diff fluid question

[donnyj08]

Going to change the diff fluid on my c5 this weekend. I can use Gm ls 75w90 but it's outrageously expensive, or my usual valvoline synpower 75w90 ls.

Valvoline customer care said in a vette to add gm ls fluid to the synpower on top of the current amount in synpower. He said each qt of synpower has 4 ounces of LS additive but I will need 4 oz more on top of that per differential fill.

Should I pay the high dealer cost for the GM fluid? Any corvette guys that can chime in on this?

 

[dnewton3]

I know that the Valvoline product meets SAE J2360. I do not see GM's fluid on the list. That does not mean the GM fluid is inadequate; it's just not validated to that high standard.

I'd use the Synpower and treat it. The cost will probably be a wash after the extra expense.

 

[stchman]

After reading the 2000 Corvette owners manual it states:

Can we assume your Corvette has a limited slip differential?

Quote:

SAE 75W-90 Synthetic Axle
Lubricant (GM Part No. 12378261
or equivalent) meeting GM
Specification 9986115. With a
complete drain and refill add
4 ounces (118 ml) of Limited-Slip
Axle Lubricant Additive (GM
Part No. 1052358 or equivalent)
where required. See “Rear Axle”
in the Index.


I would go down to the local auto parts store and buy some Mobil 1 75W-90 gear oil. You might want to stick with GM's limited slip additive. The Mobil 1 gear oil is about $10 a quart.

As far as the quantity, I would buy 4 quarts as you can take back what you don't need.

 

[donnyj08]

Originally Posted By: stchman
After reading the 2000 Corvette owners manual it states:

Can we assume your Corvette has a limited slip differential?

Quote:

SAE 75W-90 Synthetic Axle
Lubricant (GM Part No. 12378261
or equivalent) meeting GM
Specification 9986115. With a
complete drain and refill add
4 ounces (118 ml) of Limited-Slip
Axle Lubricant Additive (GM
Part No. 1052358 or equivalent)
where required. See “Rear Axle”
in the Index.


I would go down to the local auto parts store and buy some Mobil 1 75W-90 gear oil. You might want to stick with GM's limited slip additive. The Mobil 1 gear oil is about $10 a quart.

As far as the quantity, I would buy 4 quarts as you can take back what you don't need.


those part numbers have been surpassed by 88862624 LS Dexron 75w90. it includes a high level of modifier. GM designed it for the C6 Diff issues. The latest TSB is 2 bottles of Gm additive if you use the part number you listed!

also dnewton3, can i use any type of LS additive or do i need to use the GM stuff? obviously the LS additive in synpower is not GM so will it matter what brnad of LS additive i use in conjunction with Synpower 75w90?

 

[dailydriver]

I personally feel that the Motorcraft XL-3 is a better FM additive (at least in my aftermarket Eaton Posi), BUT the Getrag unit in the back of your FRC might use a limited slip with a different clutch pack setup than mine, so yes, I would stick with GM's additive.

I usually add a full 4 ounces of which ever FM additive since I do not believe that the oil companies put in as much (or as strong an) additive as they claim to their 'LS' gear oils.

 

[donnyj08]

thanks, dailydriver. Valvoline customer service also recommended adding 3-4 OZ on top of whats already in their Synpower 75w90 LS Fluid.

It may be just as cheap for me to just buy the GM LS fluid that contains extra LS additive for Corvettes. It was designed for the C6, but is backwards specd. My only reservation with the GM fluid is i believe Synpower 75W90 meets some tougher specs.

 

[stchman]

Originally Posted By: donnyj08
thanks, dailydriver. Valvoline customer service also recommended adding 3-4 OZ on top of whats already in their Synpower 75w90 LS Fluid.

It may be just as cheap for me to just buy the GM LS fluid that contains extra LS additive for Corvettes. It was designed for the C6, but is backwards specd. My only reservation with the GM fluid is i believe Synpower 75W90 meets some tougher specs.


Your owners manual states that if you do a complete drain and refill to use 75W-90 synthetic gear oil and 4 ounces of limited slip additive.

I would stick to what the owners manual states.

Mobil 1 is excellent gear oil, and GM has been using and recommending Mobil 1 lubricants for years.

 

[donnyj08]

Originally Posted By: stchman
Originally Posted By: donnyj08
thanks, dailydriver. Valvoline customer service also recommended adding 3-4 OZ on top of whats already in their Synpower 75w90 LS Fluid.

It may be just as cheap for me to just buy the GM LS fluid that contains extra LS additive for Corvettes. It was designed for the C6, but is backwards specd. My only reservation with the GM fluid is i believe Synpower 75W90 meets some tougher specs.


Your owners manual states that if you do a complete drain and refill to use 75W-90 synthetic gear oil and 4 ounces of limited slip additive.

I would stick to what the owners manual states.

Mobil 1 is excellent gear oil, and GM has been using and recommending Mobil 1 lubricants for years.


either way it will need more additive than what is in M1. GM issued a TSB to add 8oz per fill in a fluid not containing FM. they have since developed a gear oil called Dexron LS that contains the correct amount of fluid. The problem is it is 25$ a qt.

either using M1 or Synpower ill still need to add 4 extra OZ of FM to the fluid.