GV Under/Overdrive in a AC?

[Silversmith]

Has anyone installed or investagated the install of a Gear Venders Under/Overdrive in a ERA S/C Cobra? Mated to a 10 bolt top loader? The concept seems quite compelling; 8 forward gears! My driveshaft is 12.5" long. w a 427 s/o & a 10 bolt toploader. I was told min. driveshaft leingth needs to be 13.5" for a GV overdrive mount. Needless to say I won't have a driveshaft if one could be installed. The IRS has a hard mount chunk. but where to save an inch? Any thoughts??
Thanks,

[rpatton3]

Keep us posted with photos if you do it. Maybe a different yoke could solve the distance problem.

[strictlypersonl]

The drive-shaft length is not an issue with a stationary differential. The problem with adding that OD is tunnel space and interference with the chassis X-member. You're better off changing to a TKO 600 with overdrive. Lighter and cheaper to do.

[bobcowan]

8 forward gears is not that big of a deal. IMO, it's a bad deal. That's a lot of shifting. The main purpose of a seperate OD/UD unit is to be able to split the gears while shifting and keep the engine in a very narrow power band while hauling a heavy load. That's why they're such a heavy duty duty unit. You really don't need a 10,000# rating in a muscle car.

A lot of hot rodders liked to use them coupled with a C6 or TH400 because you could get an OD gear. That was back in the days before OD transmission became standard factory equipment.

Nowadays, an OD transmission is so much cheaper, lighter, and smaller that there's really no need for a separate unit. It doesn't make sense no matter how you look at it.

If I was looking for a new transmission, I'd look at the new heavy duty 6 speeds, with two OD gears.