Ransford2987

I was underneath my car today replacing the rear sway bar end links, and I saw a tag on the rear diff that said "Ratio 3.27" and then some other numbers. The Camaro data for a 1990 IROC has nothing about 3.27 gears. I have the G92 package, but I'm not sure if that makes a difference. Any ideas on why it says 3.27 instead of 3.23? The aforementioned data also says 1989 5.7s had 3.27, but everything looks factory, including the tags. Let me know what you guys think.

QUICKCHICKEN

iTrader: (12)

3.27 is the ratio for the Borg 9 bolt. the 9 bolt is a 7.75 rear whereas the standard 10 bolt is a 7.5. nothing in the 9 bolt is interchangeable with the 10 bolt. 3.23 is a 10 bolt ratio.

not to be confused with the 9 inch rear. the 9 bolt is a reasonably bit stronger than the 10 bolt. the ratios for the 9 bolt are 2.77, 3.08, 3.27,3.45. the 3.08isnt the same as the 10 bolt 3.08.

89 was the last year for the 9 but some 90 cars got them as GM was depleting their stock.

86WS6

iTrader: (1)

Consider yourself lucky to have the 9 bolt diff. I have one of each, and the 9 bolt as a stock unit is stronger then the 10 bolt is as in stock form. As for a 3:23 gear compaired to a 3:27, I doubt if one could tell the difference driving two identical cars, all things equal, except for those two gear ratios.

Ransford2987

Thanks guys. I didn't even think of counting the bolts while I was underneath the car. It makes sense that they had some 9 bolt diffs still on the shelf. Thanks again for the info!

QUICKCHICKEN

iTrader: (12)

the 9 bolt has the BORG logo on he bottom of the pumpkin and the ratio is stamped on the side of the ring gear. just roll the axle till it rolls around.

Ransford2987

I took a look today and saw this. Would I have to remove the diff cover to see the ring gear (I'm assuming so)? What's the other number on the bottom of the diff in the third picture: 323F0?

sofakingdom

iTrader: (1)

Yes.

That other number is .... a number. Nothing more. Since it was cast into the casting of the housing, as part of the housing casting operation even before the steel tubes were jammed into the cast center part, it's some sort of casting code for the casting portion of the housing; date code, factory ID, something of that nature. Nothing.

Ransford2987

I definitely appreciate all the info, guys. Thanks for the help!

QUICKCHICKEN

iTrader: (12)

yeah, you would need to remove the cover, good excuse to change the fluid. be sure t use the additive and put that in first then the fluid.

Ransford2987

Any recommendations as far as brands or types of oils/additives?

carattini

Sintech

Ransford2987

Is that how it's spelled? I can't find anything like that...

navy02ws6

Maybe they meant Castrol Syntec?

I honestly can't recommend anything, still broke two 10 bolts in my '02 with Mobil 1 synthetic, never even had slicks on the car.

You'll need a viscosity rating too, my '02 specs 75W-90, but the 9 bolt may be different.

sofakingdom

iTrader: (1)

I prefer Mobil1 personally. Though there's nothing "wrong" with the Castrol either.

No fluid will keep one of these rears (or any other) from "breaking". Best you can hope for is, keep em from WEARING OUT for as long as possible; and, make em run as efficiently (waste as little fuel) as possible in the meantime.

75W-90 is fine. Bearings, gears, axles, etc. are all pretty much the same, no matter what name is cast into the housing. Don't let the marketing dept fool you into thinking otherwise.

Ransford2987

Ok, one more question regarding diff fluid: royal purple 75W90 says you don't have to use additives, but should you add it anyway? I'm sure that stuff is engineered for LSDs, but I don't want to have issues because of it. I have a couple weeks until I can change that stuff out anyway. It's frowned upon to jack a car up in an apartment complex parking lot...

86WS6

iTrader: (1)

On my 86 I used the Lucus gear oil which does not require an additive.

My car has 29K actual miles on it, and five years ago I changed out the OE lube for the first time. The car has 25K miles on it, and the diff was so tight that it would drag a wheel going into or out of the garage. Suspecting that the OE lube has broken down, I put the Lucus gear oil in it, and it works perfectly. It is quiet and smooth, but will quickly kick in the limited slip if I get onto it. Just 2 more cents...

Ransford2987

I appreciate the info. I think I'll skip the additive. It's just one more thing that has probably become redundant with the better fluids that are made these days...at least that's my thought.