Monza factory posi rear end

[duckblaster67]

Does anyone have any production numbers for how many came with this option?

[cjbiagi]

Surprised none of the guru's responded on this, maybe there isn't a record? My guess is it's probably a fairly small percentage. It had to be ordered as a option and most likely most people didn't bother. I would guess maybe 10 - 15 % of the total?

[johnk]

Don't know how many came from the factory but mine was installed by the dealer when I purchased it with 3:90 ratio for 1/8 mile. lot of fun now restoring for the street and I am replacing it with a new 9.5' with 3:50 ratio.

[cjbiagi]

GM never made a 3.90 gear ratio. It looks like you still have the stock 4 lug 7.5" rearend in there. Where did you come up with that ratio? A Monza never came with anything numerically higher than a 3.42 gear from the factory and those were used in some 4 cylinder applications. Most V8 cars came with anything between 2.29 to 3.08 depending upon engine, trans and year.

[stage169]

If you want to see production numbers Bryan's site is the place to go for the H body. http://monza.homestead.com/files/MonzaP ... umbers.htm

RPO G80 for 1977 = 2,866 That is only 3.9% of all Monza's made for 77.

Brian

[johnk]

Clyde in the post I said the dealer installed it when I purchased it. It came with the 2.90. Yes it has a different carrier for the 3.90 with POS. and is a 7.5" stock 4X4 You can not drive on a long trip with 13" tires as it is at about 3000- 4000 RPM's at 65 MPH. But no shifts in a 1/8 mile with the powerguilde. Been in the garage sense the mid 80's That is why I have replaced it with a 9.5" so I can drive it on the road again. Just realized that the stock sway bar will not clear the new rear it is a lot bigger than I thought but I don't think I can break it

[cjbiagi]

Oh ok, my point was that GM doesn't make a 3.90 gear set for a 7.5" rear so it wouldn't matter who installed it. Your original one must have been a 2.93. GM gear sets for the 7.5" are 2.29. 2.56. 2.73. 2.93. 3.08 3.42 3.73 & possibly 4.11.

[johnk]

Clyde you might be right. They put in a 4:11 and it was too short so I took it back and they put in what they said was a 3:90 but I have never had to go into it so have not counted the teeth. LOL It's sitting on the floor right now, to make one round of the brake drum how many times should I have to turn the pinion for 3:73 ? Don't want to take the cover off unless some one wants to buy the thing right now planing on just taking to scrap yard with that low a ratio not very useful and the pos carrier is only good for a small number of ratios. I might put in the for sale section but not much hope anyone would want it. shipping would be a pain.

GM gear sets for the 7.5" are 2.29. 2.56. 2.73. 2.93. 3.08 3.42 3.73 & possibly 4.11.
JohnK

[duckblaster67]

Thanks Stage169 for the numbers and link!