4+3 overdrive trans

[928stech]

I have an 84 C4. Even though everything seems to be working ok, I would like to know what parameters this transmission works off of. Thanks..Mike

[c4c5specialist]

HI there,

Your 4+3 is basically a T10 4 speed manual transmission with a separate overdrive unit on that back that works in the 2/3/4 gear ranges.

4 speeds ,plus 3 overdrive ratios as well.

It uses the switches on the transmission to determine what gear you are in and will turn on the overdrive everytime you switch to second UNLESS you turn it off.

Allthebest, c4c5

[ChuckG]

Originally Posted by c4c5specialist

HI there,

... will turn on the overdrive everytime you switch to second UNLESS you turn it off.

Allthebest, c4c5

That is after the car coolant temp reaches 140 or so. Don't freak out if the OD won't come on for the first couple miles on a chilly day.

The OD is kinda cool. It's essentially a planetary gear box--an auto for your manual. It's less "7 speed" than 1st, 2nd, 2nd and a half, 3rd, 3rd and a half, 4th, 4th and a half, since the OD is between your T-10 gearing. I shut mine off around town and when I'm playing. The mileage penalty is only enough to worry a CAFE bureaucrat, not a Corvette owner.

Keep up on your maintenance and you'll be golden. I updated to the 1986L style and keep the fluid changed every other year. So far, no worries!