C4 --- 4 + 3 Manual Transmission Question

[Black 03 Z06]

I was reading in the latest issue of Hot Rod Magazine that Doug Nash had passed away. Nash was a successful drag racer turned transmission expert. His Doug Nash Equipment and Engineering company built the 4 + 3 transmission for the 1984 to 1988 Corvettes. According to the article it was in essence a Super T10 four speed with a two speed overdrive attached to the back of the transmission that could be engaged in 2nd, 3rd or 4th gear.

I have never driven one of these cars so I wondered what are they like to drive with that transmission? I take it they did if for fuel economy but maybe not. What was the shifter arrangement? Was the overdrive electrically engaged? Hopefully someone can let me know.

 

[NW-99SS]

Looks like you press the top of the shifter to engage the overdrive?

RIP Doug Nash

 

[Black 03 Z06]

Nice find NW, thanks for posting that.

 

[Riley P]

My friend had an 87 with a 4+3. From my recollection, the +3 was more like splitting gears than adding gears on top of the transmission. He engaged the overdrive by pulling a collar on the shifter.

 

[NW-99SS]

Maybe it's both pulling the collar and pushing the button, or one for engaging the overdrive and one for disengaging it?

 

[Range]

The collar is for reverse only.....you push the button on top to engage or dissengage. I leave it in OD 90%. Of the time....it will "downshift" like an auto if you tram on it. Much maligned tranny, drive it smoothly, service regularly, it will last. Personally, I like four gears...less,rowing"

 

[Black 03 Z06]

Thanks for the input Range. The Super T10 was a pretty stout unit in its heyday as I recall so is it the OD that is the weak link?

 

[Rmktim]

mine has the 4+3. Range drives like I do. 90% time leave the switch on. 50 km hr in second at 1900 is fine around town. Turn off to get sporty. 4th od is about 1850 or so at 100km. The little auto unit did have its problems, as range said service it lots about every 10,000 fluid change. If you are into hard core racing it will let you down. My 85 there is a od switch on the console. Trying to find someone who knows anything about them and who has worked o them is very hard.Parts still avail.

 

[Riley P]

Thanks for the clarification Range! Seems the memory or his explanation of how the OD works was a little off.

 

[CCO]

Murray, our friend Kent in Peterborough had an '88 with the D/N 4+3 .

He also may be a good source of info.

Love the thread. Learned a lot too.

Here's the thread from when Kent had it up for sale in '13. I almost bought that baby. Very nice car.

1988 Corvette C4 Base Coupe Fully Loaded

R.I.P. Doug Nash

Colin.

 

[razzyrazz]

I have a 88 with the 4+3 in it. I have only had the car for about a week and drove it 1200km to get it home from where I acquired it. To get into the auto mode you need to engage the clutch and push the button on the top of the shifter. The gear selector indicator acts as the button. This car when you start it though starts in auto mode even if auto is shut off when I turn the car off, I am not sure if it is suppose to do that or not? I run the manual gears in town and only have the auto engaged when I am on roads with speeds +70kmh. IMO it not a track transmission but on the highway I have gotten it down to 10.4L/100km and a DTE of 740km.

 

[Black 03 Z06]

Thanks for the input.

 

[VikingTrad3r]

I have a 88 with the 4+3 in it. I have only had the car for about a week and drove it 1200km to get it home from where I acquired it. To get into the auto mode you need to engage the clutch and push the button on the top of the shifter. The gear selector indicator acts as the button. This car when you start it though starts in auto mode even if auto is shut off when I turn the car off, I am not sure if it is suppose to do that or not? I run the manual gears in town and only have the auto engaged when I am on roads with speeds +70kmh. IMO it not a track transmission but on the highway I have gotten it down to 10.4L/100km and a DTE of 740km.

razzy, wouldnt it hold up fine if a person just left the od off on the track?

 

[vintageracer]

First year of the Corvette Challenge series I believe they did use the 4+3 with good results, but wouldn't be surprised if they blocked out the overdrive.