camar0corey

iTrader: (22)

OK, I have a 94 z28. Differential is stock. It has 4.10 gears with about 1500-2000 miles on them.

Don't know exactly what fluid was put in at gear install, probably non synthetic valvoline, probably whatever the factory recommends.

My dad picked me up 2 quarts of Royal Purple 75w-90 the other day. Will there be any issue when running this fluid? I think this was the fluid number at least that richmond recommends for their gears. Factory says well I don't remeber what the factory fluid recommendation was, as the Haynes dosen't list it.(I knew there was a reason I liked my Chiltons better)

Any help would be appreciated, thanks. -Corey

Silver LS1

iTrader: (3)

Absolutely not. This is great gear oil and the engine oil is even better. RP is the way to go.....

dailydriver

That IS an Auburn diff stock, right? I would just stick to a good mineral gear oil (Torco, Shaeffers, maybe Lucas in a pinch), with the 4 ounce GM (or equivalent) friction modifier additive added to the mix. Since you're in the Sunshine State there should be NO problems running an 85W/140 weight for the added protection.

camar0corey

iTrader: (22)

Well I don't know what the factory diff is. Its a 94 z28, thats about all I could tell you to figure the diff out.

The friction modifier is already in the Royal Purple though.
If I can find the receipt maybe I will take it back to get the 85w/140, but if Richmond recommends 75w/90, I shouldn't have any issue using the 75w/90 right??
I really don't think the receipt is around anymore, I don't want to break something if I put the wrong fluid in though.

I'm running RP in the engine and in the manual trans. so I would like to know if there is going to be a issue though with using their gear oil, which is already sitting in front of me, before I put it in.

camar0corey

iTrader: (22)

Sometimes I travel where it gets a little colder, I'm in PA right now on vacation, is a higher number bad then??

dailydriver

If your diff is anything other than a Torsen (or True Trac, a Torsen type diff), use a good mineral based gear oil. I am almost positive you have an Auburn diff in there (unless someone swapped out the stock unit). Synthetics could render the Auburn useless ("peg leg" burnouts, etc.), and possibly destroy the cones outright. Again, you CANNOT go wrong with a good mineral based gear oil!!
BTW; some (not all) T56 f body owners have had problems with the RP in their manual transmissions.

camar0corey

iTrader: (22)

What kind of problems have people had with the trans? I used the Max ATF, not the manual trans. fluid they offer.

I'm so fluid stupid, what is the actual difference between a 75w-90 fluid and a 85w-140?

camar0corey

iTrader: (22)

Ok, went to richmonds site and they recommend 75-140 synthetic GL-6 or higher.
Are GL numbers inversed then? IS GL 4 or 5 better or worse than 6?

So have people had their LSD break when using synthetic fluid then? I read over on royal purple's website that its perfectly fine to use with cone differentials.

dailydriver

The GL #s do not signify better or worse. They pertain to the EP (extreme pressure) and other additives contained in the gear oil. You just have to use the correct one speced by the OEM/diff/gear manufacturer. GL-6 does not exist anymore as a spec. Richmond probably specs it as their own branded gear oil carried that spec when it was current, and as one of the few with that spec at the time it was a good way to get you to buy their product.

I don't know that RP would "break" an Auburn diff, but it could render it ineffective by burning out the cone clutches. I would call Auburn directly and ask the tech people if they have any actual experience with RP gear oils in their diffs.

camar0corey

iTrader: (22)

Well the gears are getting readjusted on Friday, the installer has decided they are too noisy at low load. I did exchange the RP 75w-90 for RP 85w-140, so I will be using the heavier oil. I'm going to take my chances I guess, twisted theory on my part, but if all of these different people have put it in and dyno tested it and etc. I'm guessing it should be alright. I'm hoping major publications wouldn't put something in the vehicle that would damage or make ineffective, the LSD.

Also having a hard time finding out who made the factory LSD in a 94 z28.

KCRickSS

I had an Auburn originally and the spec sheet from SLP specifically stated to use dino + additive or the clutches will wear prematurely.

I had to have my pinion seal changed at around 4,000 miles and my Chevy dealership swore up and down that my car needed Synthetic diff oil. I showed them the spec sheet that came from SLP that said my car had an Auburn differential (as an SLP option) and to use DINO + ADDITIVE. When I picked it up I found out they put the synthetic in anyway. I was told that the drivetrain warranty would be voided if they used anything other than what the Chevy manual said is standard for my 5.7 Camaro. What a load of


Anyway, I changed the oil around 12,000 miles but my peg leg burnouts started around 20,000 miles and got progressively worse. I like to beat the car on the streets but I only had ONE autocross event and NO trips to the strip - mostly city driving to work and back. I think the 8,000 miles of synthetic oil (about a year of driving for me) wore it out quicker than normal.

I'm not sure if you have the Auburn but if you do I would highly recommend the dino oil + additive. In hindsight I wish I had changed it right away. I drove the one legged car for quite a while but I finally got a 9" with TrueTrac (Torsen type, not clutch driven like the Auburn).

seabirdak

You could try it. Gear oil is cheap for 2 quarts that will last a long time. I personally run Amsoil in my diff and transmission.