C-3 70 LT-1 driveshaft diameter

[Chuck Caldwell]

Recently purchased a 1970 LT-1 and I'm in the process of doing a total chassis/suspension restoration.

Noticed tonight that the driveshaft, rear end pinion yoke and transmission pinion yoke were all of the wrong (smaller/weaker) diameter/sizes. The previous owners must have broken a few parts racing the car in the past as the only HD driveline parts still in tact are on the half shafts connecting straps diameter. My question is what is the correct diameter/size the drive shaft supposed to be for a 70 LT-1 and I'm also assuming the front/rear pinion yokes are also supposed to be of the HD type.

Does anyone know the correct sizes and where I might find the correct parts to restore the car with.

Thanks!
Chuck Caldwell
Pewaukee, WI

[Joe L.]

Re: C-3 70 LT-1 driveshaft diameter

Chuck-----

The original driveshaft for 1970 with LT-1 had an OD of 2". The transmission yoke and differential pinion yoke (companion flange) were of the "small" finger diameter of 3.84" for 1280 series u-joints. ALL 1970 Corvettes with 4 speed transmission used this size yokes and 1280 series u-joints.

The larger diameter yokes were used for 68-70 Corvettes with THM-400 as well as most 1971+ Corvettes.

[Chuck Caldwell]

Re: C-3 70 LT-1 driveshaft diameter

Thanks Joe....I was confused because I was comparing this 70 LT-1 to my other original 71 LT-1 which does have the larger HD trans/diff pinion yokes and a larger diameter driveshaft too.

I'm suprised GM used the smaller yokes and driveshafts on the 70 LT-1 and Big Block 4 speeds which had more torque/HP than the 71 versions.

The car does have the HD yoke/u-joint caps in place though on the half shafts to the differential carrier connections and the differential carrier yokes are of the HD type.

[mike cobine]

Re: C-3 70 LT-1 driveshaft diameter

I have a feeling that the larger size may have been more to standardize sizes (reduce number of similar parts) across the line by the bean counters than to increase the heavy dutiness of the parts.

I have never known anyone with a stock Corvette to break a half shaft or a driveshaft. With roughly 600 hp out of the 427 in the race car, the only parts I broke were the posi housing in the 3.70 and ripped the clutch material off of a clutch (a triple disc remedied that).

I'm not saying it couldn't happen, as in drag racing a lot of people made a lot more horsepower, but in stock configuration, I don't think that was an issue.

The weak spots were tires and rear end.