Synth too slippery, IMHO. Use a good quality non-synth with "friction modifier".

Rich Krause

 

"Too slippery" for what senor Krause? 8 and 9 second 1/4-mile runs??

-Mindgame

 

Sure, if it gets on your tires.....

Seriously, I wouldn't argue with anyone about it. But I'm an old guy and I like to stick with what I know works. I've broken a lot of rear ends, and none of the malfunctions ever seemed related to lubrication.

As much as I spend on cars it may seem silly. But I also hate to spend more $$$ unless I can see the benefit. On that note, an 809 sec car is the last one I'd use synth in. I'd be changing the fluids prety often. In a street "set it and forget it" setup, synhth makes more sense.

Rich Krause

 

At that level Rich, you're looking for every little bit of power you can find... hence reduced friction anywhere is a good thing IMO. Why not just run dino oil in the crankcase then? I wouldn't and never have in my race motors (except maybe 15 years ago) but that's just the "racer mentality". They're even micropolishing the gear-sets now. Suppose to reduce friction and eliminate stress risers but the race guys will take every little bit they can get cause that's what it'll take to beat the guy in the other lane.

-Mindgame

 

I see your point about the friction, and was thinking about it when I posted. But I was mostly thinking in the context of the kind of racing I do - grudge matches, bragging rights, etc. It's not the kind of thing where the last 0.01sec will make a difference. If it were, I'd be there with synthetic I guess. Right now, there's synth in my crankcase and tranny but not the rear end.

Rich Krause

 

Back to my original question...

So any 80W90 will do along with GM additive?

 

I'd save few bucks compared to synth and do that.

Rich Krause

 

Not to stir the pot anymore, but we are talking less $$$ than an engine oil change. I think I paid ~8 bucks a pop for the RP at Napa. The regular stuff was around ~4-5 bucks. Also, we are talking about a longer interval than engine oil. My point is that the sub $10 difference is kinda small in the grand scheme.

I don't use synthetic motor oil because I change it too often (1500 miles - I like to see what's going on under there pretty often ), and it would cost too much. This is a little different IMO.

Besides... is Rich really talking about saving money on car parts?!

j/k Rich

Ryan

 

Yep, that is pretty ridiculous isn't it?

Rich Krause

 

i just changed to synthetic about 500 miles ago. i noticed the synthetic is cleaning out my rear. i ordered a new girdle about 100m miles ago, so i had the new synthetic in for about 400 miles or so. when i put the new girdle on, my fluid was totally black. i guess thats because of the synthetic cleaning it out. i really don't know. i am just going to flush it every couple hundred miles until its clean. it may be a little expensive to do this, but oh well. also, how do you know if you have an auburn rear??? all i know is i have a 95 z28 M6. does anyone know the option # so i can look in my glove box and see if i have it??

 

My 97SS came with Torsen and full synthetics. I'm pretty sure that when I changed it out, I used GM additive.

I now have 4.10s and will be putting in Mobil 1 with GM Additive when I change out the Dino break-in oil.

 

Remember that the additive is a "friction modifier". It allows the clutches to work. Using synthetic oil will allow too much slippage in a "clutch" type rear unless you use more additive than you are suppose to. I'm sure that synthetic will work great in torsen's and lockers, just not Auburns.

 

And again, can someone PLEASE answer my question about what a '97 Z28 has? Is it an Auburn? I must be running enough friction additive...because I have no chatter in my rear end, and I'm running Redline in it...

 

Does anyone know what the manual says as far as the oil weight for the rear end.

 

Manual recommends 90W gear oil

if you got the stock Auburn, you could run 90W dino oil w/ GM limited slip additive, or if you want synth, the 75W90 Redline gear oil is very good and it already has a friction modifier added, so don't have to buy.

if you got a stock Torsen diff, the Redline Heavy Shockproof is good. 90W but with heavy lub ability of a 240W oil (if you believe the website and bottle)

Redline tech told me the Torsen doesn't need the GM limited slip modifier cuz there's no clutches, but 75W90 would help reduce heat on the Torsen's hypoid gears. i dunno, i threw in the Heavy Shockproof, seems good. I'll leave it in there like 20,000 miles or more