Rear Differental Lubricant

[fastglass95]

What is the advantage of using an expensive synthetic rear end lubricant over standard petroleum based gear oil + posi additive as Corvettes came from the factory with?

I'm doing some service work on mine and drained out all the old stuff the previous owner put in (Red Line, heavywieght! stuff is "blue" colored) and was considering just going back to G.M. stuff the factory put in the first place!

I just don't buy into all the advertising hype!

Looking for opinions on synthetic vs. petroleum based for the rear diff.

 

[Ken]

I just don't buy into all the advertising hype!

Good for you Tom, I figured you'd be as smart as that.

The main benefit behind any synthetic lubricant is its ability to withstand higher temperatures.

There are many reasons, both pro and con, when it comes to the one's choice of hydrocarbon (petroleum) based versus synthetic oils, but even the synthetics contain a certain amount of hydrocarbon-based components.

If you like, I can do some research FOR you, and give you a more complete, and hopefully better defined, picture. :L

_ken

 

[ROCKO]

Lubricant

Tom: I've had a little experience with studies on lubricants. Back in the 1980's I was an engineer involved with the development of the camshaft for 3.8 V6 for GM part of our groups responsibility was to look at ways of reducing cam and engine wear. We called on a major lubricant supplier who provided a demonstration how different lubricants performed under load and heat. Synthetics were still new at the time, but they only performed slighly better in the friction testing than normal petroleum based lubes. After all was said and done the data showed that if you maintained your vehicle using factory recommended lubes, the life expectancy of your engine componets would meet or exceed normal engine life. Remember the factory spends alot of time engineering the components of your vehicle to work together under a variety of conditions. From extreme cold starts to desert heat. I personally believe, and it's only my opinion, that if you drive your car in normal fashion, no race tracks or etc, a fine grade oil changes at regulas intervals will provide excellent service. However synthetics do perform better under higher temperatures as Ken said. I'm gonna look to see if I can find the data for you. i'm sure I have it tucked away somewhere. Rocko:cool

 

[vms4evr]

I just had my rear gears changed. The Master install kit had Red Line in it. If it wasn't for that fact the guy would have just put the standard GM recommended lube in it. This guy has built enough Vettes that he felt if I was doing serious racing then the synthetic would pay off. At 1,000mi we're draining and refilling the rear. It will be the GM recommended.
I also tried Red Line synthetic oil in the engine. Again, no real racing, so it wasn't worth the extra $3/qt. I'm going back to Mobil 1 for the engine.
Graham

 

[fastglass95]

I guess I should add that the rear has been up-graded from the pathetic 2:59 gear ratio to a more liveable 3:73 when the synthetic gear oil was installed.

I do autocross this car, but only parking lot stuff, no real extended track time is seen.

I am leaning towards the regular petroleum based stuff. Just changing it out every 2 years or so.

I do use Mobil1 for motor oil as per G.M. specs.

 

[Hib Halverson]

I'm doing some service work on mine and drained out all the old stuff the previous owner put in (Red Line, heavywieght! stuff is "blue" colored) and
(snip)

Somehow, the previous owner got the wrong Shockproof product in that rear axle. If the lubricant was blue, it was Light Shockproof. Use of Light Shockproof in a Corvette axle is
not advised at this time. While there is reason to believe Light can be used in road car rear axles, no significant testing has been completed to support that. The proper product in the Shockproof series to use in a street-driven rear axle is Heavy and it's redish-pink in color along with being somewhat more viscous.

I'd be interested to know the mileage since the fluid was last changed and how the rear axle was performing.

Now, the question: why use a synthetic? One of the C4 rear axle's weaknesses is temperature. It's in a place that doesn't get much airflow and it's sitting above the exhaust. In fact, a common modification for endurance racers is a rear axle cooler. For street high performance use, a synthetic rear axle lube is more tolerant of high temperature and high shear, both conditions that occur in C4 axles. The Shockproof is even better because its extreme pressure additive package is primarily calcium-based rather than sulfer based and works better. The Shockproof line was originally developed for one purpose: to improve ring-and-pinon durability in off-road race trucks. The shock loads to the gears when the trucks get airborne is significant.

I've been running tests on Shockproof in road cars for about five years. In one test, using a pick-up truck, the rear axle lube (Heavy SP) went 100,000 miles with no change. Spectrographic analysis showed little metallic residue on the lube and way less than would be expected at that mileage. It also showed the lube itself was in good condition. Visual inspection of the gears showed the same. I've also run it to 46,000 miles in a SUV front and rear axles and to 32,000 miles in a ZR1. With the ZR1.

I use Heavy Shockproof in all my rear axles that are in high-performance cars and trucks.

 

[Ken]

Hey Tom, here's a link to Redline ShockProof Gear Oil.

_ken

 

[69MyWay]

For mostly street use, I would suggest only using the factory recommended fluids and additives available at any G.M. dealership.

 

[maxrevs85]

When it comes to lubricants, I highly recommend mobile one synthetics . I have used these products for years. In race cars and street cars and tow vehicles. Wear was all but non exsistent. Race engines that came apart after a season were clean and bearings and all metal surfaces were in excellant condition. It seems to hold up undre extreme heat very well. The engines were 6 to 700 hp high dollar motors(running8000 to 8600 rpm's) and the rear ends were anything from 9"fords to mostly quick change differentals that took alot of abuse and shock load. I have never been in favor of redline oil. I believe it is over rated. In actual comparrisons and testing , you would like the visual results of the Mobil One. Just my .02 cents

 

[vigman]

Well if nothing else...

Your saving whales......
I have always used the GM lubricant for the rear end of ALL my previous Vettes & current ones too!
I don't race....I don't have any problems, well with my rear end..no wait, my limited slip differential.


My.02
Mike

 

[vms4evr]

I guess I should add that the rear has been up-graded from the pathetic 2:59 gear ratio to a more liveable 3:73 when the synthetic gear oil was installed.

I do autocross this car, but only parking lot stuff, no real extended track time is seen.

I am leaning towards the regular petroleum based stuff. Just changing it out every 2 years or so.

I do use Mobil1 for motor oil as per G.M. specs.

Yeah mine was converted from the pathetic, as you mentioned, 2.59. I went to 3.54 instead of 3.73. Much better out of the hole. The guy still insisted that there was no reason to use the Red Line. He also mentioned not to do lots of drag racing, strip type that is, as the Dana 36 won't take the abuse. So unless you have an overwhelming desire to pay the premium for Red Line the factory recommended will work fine.
Graham

 

[fastglass95]

I'd be interested to know the mileage since the fluid was last changed and how the rear axle was performing.

Mr. Halverson,
The rear end gears were changed from 2:59 to 3:73 at approx. 10,000 miles (almost brand new) at that time this "Blue" stuff was installed along with one 4oz. bottle of GM additive by previous owner. (work was done by a local speed shop)
Now it has 23,000 miles total and all I am doing is replacing a leaking drive pinion seal because I am anal about oil leaking from my Vettes. It wasn't leaking bad, but I'm a glutten for punishment!
So I have not taken the cover off the rear end to inspect. But it was performing flawlessly as far as I could tell. No chatter, or funky noises or anything un-usual.

Thanks for your input Hib.....and everyone else also!

 

[Ken]

Hittin' the NCCCNet too for advice, eh Tom? :L I saw your message.

_ken

 

[fastglass95]

I guess what I want is the "Heavy" Red Line shockproof oil, but I cannot find it anywhere!

Anybody know who sells Red Line "heavy" shockproof gear oil via mail order???

Ken, I guess that means you stray once in awhile too, huh! :nono

 

[Ken]

I don't conside it "straying", it's just another membership like the NCOA, COA, or the Museum, not another Corvette forum. :L

I get the e-mails (on the mailing list). Did you see "Lawrence Pagliaro's" feedback to you yet?

_ken

 

[fastglass95]

Ken, I'm not on the mailing list from there. I just check the site now and then. Usually very BORING chatter.

Larry is one of 84c4's main competitors in the autocross arena.

I'm not real crazy about Mobil1 for gear lube, If I go synthetic, I'm goin' all the way! ShockProof me baby! or I'll go with regular Havoline 90w-140 stuff or equivilent, and change it regularly.

Go Rams!!!

 

[84c4]

Hey Tom,

You want to know what I use in my farm car?

Sorry, can't tell Ya.:booty

See ya at the meeting Thursday.

Dave

 

[fastglass95]

Thank you Mr. Hib Halverson,

I went with the Redline "Shockproof" heavyweight oil in the rear end. Had a local speed shop order me some, they matched the "online price" for me.

Right on the blue stuff as being lightweight, the heavyweight is red / pink in color. Came highly recommended for autocross usage.

Redline states that the G.M. posi-additive is not needed, but should be included in cars driven mostly on the street. Heavyweight contains 3% friction modifyer right out of the bottle, they recommend 5% for street applications (about 2 oz. of the G.M. additive) added to the heavyweight gear oil.

Now, I just need to find an easier way to fill the rear-diff. with oil without spilling half of it on the ground! ad Any tips on filling the rear-end?;help ;help

 

[Ken]

Do you have a vacuum device Tom, like the Mite-y-vac or something similar that you can use to transfer liquid?

_ken

 

[fastglass95]

Do you have a vacuum device Tom, like the Mite-y-vac or something similar that you can use to transfer liquid?

_ken

Yea, I have a mity-vac, I use it only for bleeding brakes! Didn't know you could transfer liquid with it?
Guess I need to try and find the instruction manual for it:confused