Car is a 85 Iroc w/TPI. The SPID show G92, GU6 but no G80.......did all G92 cars get posi-trac? Thanks in advance. It also has 4 wheel disc brakes.

 

Can you post your a picture of your spid? What month was your car made?

 

No not all of the LB9 TPI cars got positraction from the factory.

Not all of the L69 305 H.O. motors got positraction either.

Positraction was manditory with the L98's though.

It's just kind of strange because the L69, LB9, L98 engines were the high performance engines from the factory so you think that they all should have had the performance related drivetrain options to support that.

I'm sure it has to do with economics. I'm sure GM was able to produce non-positraction rear ends at a lower cost than positraction rears.

 

Does your car have B4Z,Z28 and 1C5? If it does have 1C5 then you have a California Iroc. None of them had G80, but did have everything else you said yours has.

Post a picture of your RPOs or list the Vin# and all the RPOs if you want to check it.

Here is a California IROC to compare your RPOs to.

https://www.thirdgen.org/forums/hist...-code-z5v.html

 

Not a California car, Blue, true Iroc. I'll take the cover off, when I remove it (parts car) wish they could have put G80 on the SPID or someone knew if G80 was mandatory with G92. I'll try to find the VIN tonight, car is at my storage location.

 

I don't think that the G92 option automatically selected G80 positraction for the LB9 cars all the time. A lot of LB9/700r4 cars didn't come with positraction even if they had the G92 option though.

For the 1985 LB9 IROC the 3.42 gears were the G92 option and I think 3.23 gears were the non-G92 axle ratio option. G80 positraction wasn't manditory though with the LB9

I don't think that the regular Z28 LB9 cars got 3.42 gears, I think that was just reserved for the IROC's. Many 1985 LB9 Z28's got 3.23, 3.08 gears, and 2.73 gears. Not all of them had positraction.


Check out these links below. They have transmission and rear axle gear information

https://www.thirdgen.org/calculations

https://www.thirdgen.org/1985-chevy-camaro

I know that with the '89-'92 cars that the G92 option (LB9 & L98) included some other performance options and a positraction rear end was manditory just like with all the L98 cars posi was manditory.

 

RPO G92 and G80 were extra cost options and were not required unless you ordered them .

 

here is more on the G92 and G80 options.

https://www.thirdgen.org/forums/hist...2-mystery.html

 

I know this is an old thread, but just came across a 1985 IROC Z with G80 (posi) and GU6 (3:42) SPI codes, but missing is the G92. From my recollection (owned 1985 IROC Z in the 80s) my G92 LB9 IROC had a 3:42. It leads me to wonder if the G92 was normally "special order", but it was possible to yield the same result simply by selecting the G80, GU6 combo.

 

My friend has a 1985 IROC-Z and it a LB9 (5.0L TPI) MX0/MD8 (700R4) J50 J42 (Front Cast Iron Disc/Rear Aluminum Drum Brakes) CC1 (T-tops) G80 (Limited Slip) GU6 (3.42 to 1).

His IROC-Z also doesn't have G92 on the SPID Label.

 

Not sure when G92 (some kind of "performance gear ratio" verbage, but also in some years included various other things) was introduced. In the early years you could just order gear ratios by their RPO code; so for example, in 84 the L69 auto cars came with either 3.42 or 3.73, but AFAIK the 3.73s weren't labelled "G92".

G80 is "posi". Generally an Auburn in the 10-bolts although some esp in early years got the Grenade-Lock, or a cone type deal in the 9-bolts. G80 may have been included in the G92 package in later years, when it also included for example the dual-cat option.

MANY cars esp in the earlier years didn't get posi; GM couldn't get enough of them. My 83 L69 Z28 came with 3.73 and aluminum drum rear brakes but no posi. I put an axle from about 91-92 in it around 2000 or so, with an Eaton posi, the stock gears, and PBR brakes.

 

My 3.73 aluminum drum rear-end came out of a '84 L-69 Z-28 with auto trans. It is not a posi. I have a new Eaton style posi for it but need to get new axles before I install it...

 

As has been mentioned, I'd like to see the SPID. All 1985 IROCs I've seen with an LB9 got the GU6, (3.42) gears without the G92 code. 1985 had a posi shortage roughly around May, So after that, no posi.