1981 Optional G92 Performance Axle Ratio???

[81vette]

Since there are so many 81' on here I have a question for you guys that's been bugging me for quite a while.

I've read many places that the 81's only came with 2.72 for the 4spd, and 2.87 for the automatics. However, there was an optional G92 Performance Axle Ratio available that year....of which there were 2400 purchased. I've often wondered what that G92 ratio was. If it was the 2.87 ratio then it must have only been available with the MM4 (4spd) option as the automatic already had it. If it was the 2.87 then it wasn't much of a performance option.

Additionally, in my owners manual it list a 3.07 axle ratio in a chart and refers to it as a high performance axle ratio. This leads me to believe that the G92 option may have been the 3.07 rear that was first installed in the 80' rear axle. I'm stretching here, but maybe GM had 2400 3.07's left over from the previous year, and decided to offer it as a performance option on the 81'. I've never read anywhere what the ratio actually was for the G92 option. Does anyone have any additional information on this?

 

[Tom Bryant]

It seems to me that you are right about the 3.07 being the perf axle ratio but I'm not at home where my books are right now. Did you check the specifications for '81 here on the CAC? Maybe it tells there.

Tom

 

[fastred87vette]

:confused any answer on that... i will have a look on a 4 speed 81 this week end and wandered what is the answer and why the ratio so looow on 80 and up cars my 79 was auto/3.55 but doing 3100 rpm at 60mph:W i have since own 2 c4's with 3.07 and o/d but i now want to go backward to c3's... btw where are rpo listed on late c3's? thanks in advance!!! pat

 

[6880 Mike]

The 81 owners manual will probably list ratios.

 

[Hib Halverson]

"G92" has been the RPO for a "perf axle ratio" for automatic trans cars since the late-70s/early-80s.

That the number of cars built in MY81 with G92 is so small, the answer to the question "What was the actual G92 ratio" may be a challenge to answer.

What's in the Owner's Manual might be a clue but won't really be conclusive as Owner's Manuals often contain errors.

Since the axle in 80-82 uses the D-44 gearset and diff, as did the 85-96 manuals, I'll guess is that G92 in MY81 was a 3.07 ratio and was available only with automatics.

It'd be interesting to find someone with one of the G92-equipped 81s and get them to check the ratio by marking the driveshaft and tire then turning the tire once and counting the number of driveshaft turns.

 

[Yoda]

Ditto on what has been said

Not sure if this will answer the other part of your question or not...

The RPO's for the 1981 would be listed on the Window Sticker or the Build Sheet from the factory. I don't know of any other place on the car that has the RPO's listed. There is a information on the door about tire size that came with it, and on the door frame is the Trim Tag that ID's the paint color and interior color (Leather or Cloth)

If the car you are looking at was built in St. Louis then do a search here on the Action Center to find the "Company" will sell you a copy of the "build sheet". If it was built at Bowling Green then you can contact the National Corvette Museum for a copy of the "build sheet & or window sticker" both place's charge a "fee" for their material and service.

The List of RPO's for 1981 can be found here at the Action Center under the heading Specs then click on 1981 or you can research it at the L81VetteRegistry under the Tech Center header.

Good hunting hope you bag your limit

Bud

 

[Hib Halverson]

The issue is not whether or not there was such an RPO or how someone might determine if the car had RPO G92.

The issues is what axle ratio was in a car equipped with G92.

What we need is someone having an 81 w. G92 to measure the ratio.

Either that or get some answers from a credible source. The guy who was the powertrain development chief back then is retired-GM and a friend of mine. I've contacted him asking the question. If he can remember, I ought to have an answer soon.

 

[Yoda]

The issue is not whether or not there was such an RPO or how someone might determine if the car had RPO G92.

The issues is what axle ratio was in a car equipped with G92.

What we need is someone having an 81 w. G92 to measure the ratio.

Either that or get some answers from a credible source. The guy who was the powertrain development chief back then is retired-GM and a friend of mine. I've contacted him asking the question. If he can remember, I ought to have an answer soon.

Good luck Hib. I didn't question IF there was an option G92, if that is what you were aiming at, I was referencing to:

:confused any answer on that... i will have a look on a 4 speed 81 this week end and wandered what is the answer and why the ratio so looow on 80 and up cars my 79 was auto/3.55 but doing 3100 rpm at 60mph:W i have since own 2 c4's with 3.07 and o/d but i now want to go backward to c3's... btw where are rpo listed on late c3's? thanks in advance!!! pat

Bud

 

[bucket]

Since there are so many 81' on here I have a question for you guys that's been bugging me for quite a while.

I've read many places that the 81's only came with 2.72 for the 4spd, and 2.87 for the automatics. However, there was an optional G92 Performance Axle Ratio available that year....of which there were 2400 purchased. I've often wondered what that G92 ratio was. If it was the 2.87 ratio then it must have only been available with the MM4 (4spd) option as the automatic already had it. If it was the 2.87 then it wasn't much of a performance option.

Additionally, in my owners manual it list a 3.07 axle ratio in a chart and refers to it as a high performance axle ratio. This leads me to believe that the G92 option may have been the 3.07 rear that was first installed in the 80' rear axle. I'm stretching here, but maybe GM had 2400 3.07's left over from the previous year, and decided to offer it as a performance option on the 81'. I've never read anywhere what the ratio actually was for the G92 option. Does anyone have any additional information on this?

..................
wasnt much of a performance option...???
only if you want to go fast

 

[JohnZ]

NCRS specs only list two available axle codes for '81 (OJ for the 2.87 automatic, OK for the 2.72 4-speed); G92 probably got you the 2.87 with a 4-speed.

 

[Hib Halverson]

I emailed Jim Ingle yesterday and he can't remember what ratio G92 was. Ingle did powertrain development for Corvette back then.

 

[pbcanney]

interesting thread. I have no idea if this option is in mine but I do know (doing the wheel/driveshaft count) that mine is 3 and 1/2 turns. However, neither my son or I ever changed that from the 2.87 we presumed was in there. The car was in such run down and beat shape when we got it, I doubt anyone actually had the ring/pinion swapped in it's previous ownership (pre-1995).

I never really noticed the G92 option before and am very curious now what the details on it are.

 

[GerryLP]

Gail's build sheet clearly says RPO "HK1 2.87 axle", so my Vette does not have it either.