Pure Stock Muscle Car Drag Race

[Rowdy Rat]

Joe,

I'm afraid that I don't have a 1969 Corvette standard order form close by, but if I remember correctly, the form is very similar to the standard Camaro form you are referring to. The code ZQ9 that you mention is most likely the standard rear axle available with a given engine/transmission combination (the ZQ code was used to designate standard equipment - for the 1969 Corvette ZQ3 was the base 350/300 engine, ZQ4 was the standard black vinyl interior, etc.). Any deviations from the standard gear ratio would be noted on the order form.

Available rear axle ratios for the 1969 Corvette ranged from 2.73 to 4.56 to 1, although not all gear ratios were available for a given engine. The solid lifter big blocks equipped with manual transmissions typically received the widest range available; for an L-71 or L-89 car with an M-21, this would include a 3.36 (economy), 3.55 (standard), 3.70 (performance), and 4.11 (special). The L-88 or ZL-1 Corvettes with M-22s would have all of the previously mentioned ratios available plus the 4.56 (special). For the L-71/L-89/L-88/ZL-1 cars backed by the M-40 automatic, the gear ratios were cosiderablly restricted (much more so than with the L-72/L-78 cars in the rest of the Chevrolet line up). Available ratios included a 2.73 (economy), 3.08 (standard), and a 3.36 (performance).

The high performance automatic transmission Corvettes are quite rare; I believe the general figure quoted for the solid lifter 1969 M-40 cars is 255 L-71s and L-89s plus an additional 17 installed in L-88s. I'm not sure that the automatic car would be the best choice for a completely stock drag car due to the relatively tall rear axle ratio you'd be stuck with. Hot Rod tested an L-88/M-40 convertible back in 1969 and turned a respectable 13.5 @ 111 or so, but even they complained about the 3.36 rear. Of course, if the rules allow ANY rear axle ratio available, then you just might have something!

Hope this information helps.

Regards,

Stan

[Charley Lillard]

I used to have a 68 L78 Chevelle with 488 gears, M22 and a Window Sticker showing it came that way. It is now in the Chicago area. Good candidate ?

[JoeC]

I misread the '69 Camaro order form. You are right Stan. There appears to be four selections under the "AXLE, REAR" heading. RPO's G80, ZQ8, ZQ9 and the fourth box is the blank space to write in a ratio. Then the power team chart has four columes Std, Econ, Perf, and Spec. My question is if you could have writen in "4:11" on the Corvette order blank for a TH400 L71/L89 or L88 or ZL1 would it be factory installed or dealer installed? I do not have a power team chart for the 1969 Corvette. The 1969 Camaro Power Team Chart goes up to 4:10 and the '68 and '67 goes up to 4:88. One book lists a 1969 Camaro COPO #9511 code DT 4:56 rear.
Maybe the '68 Chevelle Charley had was ordered by writing in the ratio. Yes Charley that 68 Chevelle would have been a "Contenddaa"

[Rowdy Rat]

Joe,

I'm sure that any available ratio could have been written in, but I doubt that it would have done any good without some sort of central office override. The Corvette power team chart shows a 3.36 rear as the only "performance" ratio available with the L-71/L-89/L-88 and M-40, with no "special" ratios available. For whatever reason, the engineers decided that the most aggressive rear axle ratio a person could get in a Corvette with an automatic and one of the the solid lifter engines was a 3.36. They even created a special broadcast code (AX) for this application even though a "big block" 3.36 rear already existed (although to my knowledge, there is no physical difference between the two). What I was never able to understand is why the higher numerical ratios were never offered. The COPO Camaros and Chevelles could get a 4.10 (maybe even a 4.56) as you stated. Plus, there was no doubt that the L-88/M-40 cars were built solely to make that combination legal for stock class drag racing, so why saddle the car with a rear gear totally unsuitable for its intended purpose.

For general information, the transmission used is nearly identical to the COPO Camaro/Chevelle/Nova THM400s although the Corvette version carried a "CY" broadcast code.

I've been fortunate to see quite a few of these automatic transmission L-71/L-89/L-88 Corvettes in person and with only one exception, the cars all had the 3.36 rear (the one car that did not was an L-89 with a 3.08). I've heard recently of an L-89/M-40 car with a 3.70 rear axle (supposedly with paperwork), but I have not seen any documentation to this point. If I ever get to see the car and the paperwork, I'll let you know what I discover.

Charley, that Chevelle, sounds like a great combination! It also sounds like you've had (and still have) some really outstanding cars!

Regards,

Stan

[Charley Lillard]

The Chevelle was Grotto Blue with Parchment bucket interior, manual steering, guages, no colsole. It even showed Simulated Mag Wheel covers on the Window Sticker. It went to Dave Simpsom in St. Charles Ill. Most of his collection was bought by Mecum auctions about a year ago then resold. The current owner only has a copy of the Window sticker. Simpson either lost or kept the orig. one. What a shame.

[sixtiesmuscle]

Re: the availability of taller gears in L71, etc. vettes, could the engineers have been afraid of the massive torque ripping the axles apart? My experience has been that the Corvette rear end wouldn't stand up to the same stresses that a 12 bolt will. It could have been strictly a warranty issue. For instance, Pontiac wouldn't offer a solid lifter car for street use,i.e., with a warranty, if my memory serves me. This was because they didn't want the added liability .

[JoeC]

The only reason I can think of that they offered no higher then 3:36 ratio is because of potential TH400 trans oil temp. problems. There was some problems with overheating with the 68 Corvette big blocks and some changes were made in 1969 but engineering may have felt the increased trans RPM with a 4:11 ratio would have caused high temps. in the trans oil cooler thus in the radiator. While the Corvette slanted radiator was good for bouncing a radar signal, it may not have worked as well as the Camaro/Chevelle set-up that did use the TH400 with the 4:10 ratio. Just guessing here.