I apologize for the "pinhead" remark there. I find your irrational responses frustrating, but it's hardly anything worth getting bent out of shape over.

 

FWIW. Our Dana diffs are limited slip, not locking. There is a large diff.

 

when i installed my new rear last year that i purchased from Ikerds, it specifically said NOT to use synthetic oil for the first 1,000 miles. It said to use 80-140w conventional oil.

 

Apology accepted. No hard feelings; just a lively debate.

But consider me completely unconconviced that a synthetic would perform better in our Danas than the petro lube recommended by the folks who design, manufacture, service, and sell the differential. For the 4th or 5th time, if synthetics; performed better, extended service intervals, provided better mileage, ran cooler, and reduced warranty expenses, why didn't Dana and Chevrolet recommend syns? The only attempt to address this question was the answer that 'Chevy often didn't use the best products'. This is far from a convincing arguement in this case.

Also, nobody has forwarded any credible evidence (non-marketing materials) showing that for limited slip diffs, that petro and synthetics can be swapped back and forth without altering limited slip charactoristics (sorry, but the Amsoil white-paper is hardly an unbiased source). Can somebody show me a make and model of a limited slip differential carrier for which the engineers for the product recommend both synthertics and petro lubes?...that it makes no difference which you use. (Again, limited slip or positraction).

Eaton,..no. Dana, no. Auburn gear, no. (Auburn is new to the discussion. Click on this link then click 'limited-slip' then note their lube recommendation on page 2 of the doc, under "Important Lubrication Note").

http://www.auburngear.com/aftermarke...6pagesize%3d20

Again, I seem to be only one with supporting evidence from the engineers from Dana, Eaton, and now Auburn. The only supporting evidence to contradict so far is a white paper from Amsoil.

 

And what did they say to use after

 

From the 1996 Dodge Viper Service Manual:

RECOMMENDED LUBRICANT
All Vipers are equipped with a limited slip differential. Mopar Hypoid Gear Additive should be added if the fluid was replaced.

The lubricants recommended for this differential is Mopar High Performance Synthetic Axle Lube SAE 75 W/140 (MS-8985) A container of Mopar Gear Additive (friction modifier) should also be added after a lubricant change.

The rear axle on this vehicle receives limited amounts of air flow for cooling. Temperatures within the axle can reach as high as 300° F. (149°C.) Only synthetic axle lube provides optimum protection and durability under extreme temperatures. The use of petroleum based axle lubricants may break down under these conditions.

WARNING: THE USE OF PETROLEUM BASED REAR AXLE LUBRICANTS MAY CAUSE PREMATURE AXLE FAILURE.

The lubricant should be drained and refilled every 22,500 miles under normal use and 9000 miles under severe use.

 

Good info and if I recall correctly the Viper also has a Dana rear

 

Correct, they are all Dana 44s with clutch type limited slip.

 

http://www2.dana.com/pdf/AXSM-0053.pdf

DIFFERENTIAL LUBRICATION
It is not our intent to recommend any particular brand or make of lubricant for the Spicer hypoid axle. However, an S.A.E.
8OW-90 multi-purpose gear lubricant meeting Mil. Spec. L-2105C, and suitable for 1 A.P.I. Service Classification GL5, is
suggested as a minimum requirement.

IMPORTANT
Motor vehicles are operated under various requirements, conditions, and environments. This manual specifies
the minimum requirements that the lubricants should meet. However, it is recommended that the lubricants
specified by the vehicle manufacturer be used. They may provide additional lubricating characteristics which may
be required for your vehicle’s operation. Contact your local service dealer or refer to your owner’s manual for
obtaining the proper lubricant specification.

AXLE LUBRICANT CHANGE SCHEDULE
The following schedule is a suggested lubricant change schedule. Lubricant in your vehicle may require more frequent
changes depending upon the environment in which it is operated in. Contact your local service dealer or refer to your
owner’s manual for obtaining the proper lubricant change schedule for your vehicle.
Drain lubricant at first oil change and refill with specified lubricant. FOR NORMAL ON HIGHWAY USE, change
lubricant every 100,000 miles or 24 months, whichever comes first. FOR OFF HIGHWAY, SANDY, DUSTY, OR WET
CONDITIONS, change lubricant every 25,000 miles or 6 months, whichever comes first.
Lubricant may be drained by removing the carrier cover plate. This also allows for visual inspection of the internal
components. Follow the service procedure in the manual for reassembly of the cover plate.

 

This is why I use synthetic for my track use car. I have no idea what the diff runs at since there is no sensor, and no cooler. I've seen a lot of C5 cars address those issues.

 

 

Drivetrain - Recommended Axle Lubricant

File In Section: 0 - General Information

Bulletin No.: 76-02-02A

Date: October, 1998

INFORMATION
Subject:
Recommended Axle Lubricant

Models:
1999 and Prior Rear Wheel Drive Passenger Cars, Light and Medium Duty Trucks, and Four Wheel Drive Vehicles, 1998 and prior Corvette, Camaro, Firebird

This bulletin is being revised to add the 1998 and 1999 Model Years and add Vehicle Line and Recommended Axle Lubricant Information. Please discard Corporate Bulletin Number 76-02-02 (Section 0 - General Information).

The following tables provide the latest information on recommended axle lubricant.




WELL THE PICTURE WILL NOT TRANSFER BUT!

USE ONLY GM PART #12345977 PLUS 4 OUNCES OF GM PART#1052358 ADDITIVE.




Parts Information

Parts are currently available from GMSPO.

 

I would assume(risky) that the clutch material in these vipers is designed for synthetics, where the Corvettes may not be. Excessive slip would cause incorrect operation, and premature failure. If in doubt, go with what is proven to work.

 

I agree that there are a lot of assumptions throughout the entire thread, checking the number you posted from the TSB (12345977) I do not see it listed as currently available from GM.
I only posted the Viper information to show a different view from another manufacturer using a similar axle.
My personal view is that either lubricant will suffice, in part I base that
"assumption" on the other thread (poll) started by the OP showing a wide range of lubricants in use by C4 owners with little mention of dire consequences caused by either synthetic or petroleum based gear oil. I also know I have experienced no problems with my own car using synthetic to this point.
Just as in engine oil preference threads everyone has an opinion, suppose we all consider ourselves experts once we have changed oil once, right?

 

Your initial contention was that synthetic is unsuitable for use in the diff. Is it now that, while suitable, it may provide negligible benefit?

Also, to make my opinion clear, yes I find the cost to GM quite compelling and believable as a reason. If a cheaper fluid is likely to work well enough that the car should not suffer failures after a reasonable time (which you might define as the warranty period, or maybe slightly longer) then it is good enough.

I also would not be shocked to find the decisions were even more calculated in that synthetic fluid in every C4 would cost $X amount more. If the expected failure rate from dino fluid vs syn was expected to cost less than $X amount, you have a financial case to use the cheaper fluid.

I'd also throw out anecdotal evidence that GM and others used synthetics when extreme use was expected. If you read about the ZR-1's 24 hour enduro or the Corvette Challenge cars or anything like that, there are frequently mentions of going to all synthetic fluids. I even recall reading about them having AC use Mobil 1 grease when assembling wheel bearings for some of these extreme-use cars because the lube cooked off when using production ones. I think it was in Dave McLellan's book and about the Challenge series, but can't recall exactly.

However, I don't think anyone is saying using GM's recommendation is a bad idea.

 

I just can't wrap my head around your continued mention of the Dana doc. It does not say petroleum based lubricants are acceptable any more than it says sythetics are. I could use the same doc and say Dana only recommends synthetics. And if you want to convince me otherwise, show me where in the doc it says you can use petrol lube.

That said, if nothing else comes from this, at least I saw that doc. It was interesting to see what Dana suggests for the differential compared to GM's info in the FSM.

 

lol, yeah I wasn't bashing ya. Like I say there are just a crap load of materials out there that vary from mfg. to mfg. There has been updates to the recommended oils and it has never been synthetic for the Vettes. I would hate to use something that nobody has been willing to say screwed their car up. Kinda like full ceramic brakes on non-ceramic set rotors The additive they recommend is no doubt a whale oil substitute as is the BG stuff. Just keeps the clutches from sticking. I had my truck skipping a tire in the dirt until I started using the additives and it was gone. Synthetic is some DAMN slippery stuff, I would(IMHO) be concerned about it being too slippery.

 

.....from the peanut gallery. In the "other owner's manual" that came with my 90 ZR-1 it says in the "Track Usage" section of the manual that all the car's fluids should be changed over to synthetics. It specifically calls out the trans, rear gear and engine oil and P/S fluid.....strange that they leave out the brake fluid? Although they do say to take off the two outer spoilers to aid in brake rotor cooling for road course use.

Just thought I'd throw that out as most of us have D44's if we have the 6spd.


Tom

 

Can You put up a scan of that

 

I will try to see what I can do about that. Forgive me as I'm not a very skilled PC user...I'm an analog kind of fossil........


Truly, if ya know anyone with a ZR-1...the owner's kit, aka "pizza box", has another owner's manual in it with all kinds of info not found in the 'regular' owner's manual....it's ZR-1 option specific...but since it's just that the LT5 is the real major mechanical difference among C4's. I don't see why the info wouldn't apply to any C4....?


Tom