mikewilson88

Ok so I am new to the site and corvettes. I am looking at a 1985 4+3 and was told buy the owner the overdrive is automatic but I thought they were all on a switch am iI wrong? I have tried google but found nothing.

DanielRicany

Yes the overdrive is activated by a switch.

HlhnEast

But if the switch is in the on position, it will work automatically. You will find that the OD is a dog in second and you may not want it on all the time. I use mine for a fifth gear and its off when in the city mostly.

mikewilson88

Thank for the quick reply. Is the switch on the shifter I tried to push down on it but it felt solid there are some buttons on the console but they have no writing on them it looks like they may be for a heated seat? Sorry for all the questions but I didn't even know about a 4+3 until 3 days ago

QCVette

Like stated, the switch in the on position enables the OD to work automatically. The switch in the off position disables the OD.

On my '85 and '87 I found that I used it like a 5 speed too. I kept the switch off until I was on the highway and/or wanted to shift to OD.

Here is a chart that shows the operation.

http://www.5speeds.com/43table.htm

The switch was on the console in '84 and mid year '85 (and after) it moved to the center of the shifter ****.

mikewilson88

Ok so it may be on the console thanks for all the info I look at the car again today and I'll see if I can find the switch thanks again

DanielRicany

The switch is on the drivers side. It's right in front of the tray on the center console.

c4cruiser

Ask the owner to show you what the various center console switches do. The C4 didn't have heated seats as an option.

The power window switches are on the console. There is one switch between them that energizes either the left and right outside power mirror. A toggle-style switch in the small storage box controls mirror operation. A power seat switch is also in there if the car had that option.

If the car has the rear window and outside mirror defogger, there will be a rotary switch on the right side of the heater controls.

383LPE

no offence intended, but you might consider doing yourself a favor and avoid the 4+3 models unless your just really a fan.

DanielRicany

There's nothing wrong with owning a 4+3.

jv9999

They actually work quite well if you ignore the upshift indicator and keep the OD fluid clean and full.

DanielRicany

1985 doesn't have the upshift indicator!

pezter22

I have a '84 that used to have a 4+3. I loved it until the OD unit began to die. Instead of rebuilding it, I chose to have a Tremec TKO600 installed. It was pricey, but much better than the 4+3.

DanielRicany

I broke my 4+3 when I had the Trans out. I fixed it myself but it's really hard to get parts for it. Had to wait a month before I found the parts.

Garrys85

I recently bought an 85 and it's been lowered an inch and a half. Any idea if I'd be able to replace the 16 inch tires with 17 inch wheels, tires?

DanielRicany

If the width is the same there is no problem at all because you should not be changing the outer tire diameter. However, I'm not sure about wider rims and tires on a lowered car. I know a '85 can fit 315s no problem with the stock outer diameter on stock height.

tunedport85inject

i can understand 85 manual owners defending their cars,but ,it's a fact,the dough nash isn't the best manual ever built.The best choice for a manual is a ZF6 transmission and you can find it starting from 89 MY.If you are valuating a C4 i would advice a 89 MY as a MAF car,or i would go to a speed density 90-91 My.These car are the best final production unit of their generation with all improvements and bugs fixed over the years.I own an 85 ,this is a one year car,very special car since it comes with unic feature like forged pistons i.e,but this MY has more cons vs pros,belive me i own one,it's my car and i love it, but i know there's more and best from next MYs. i would consider a 89 as MAF car ,or a 91 as a speed density TPI, stick or auto.

mikewilson88

Ok so I picked up the car today it runs and drives fine the only problem I am having is I can't tell if the overdrive is on or off I havent really driven it much just about 3 miles home I believe I found the switch but don't know where on or off is lol as far as indicators go the gauge cluster is Burnt out this is my first vette so I'm pretty lost. Also can someone tell me how to check the fluid in the overdrive?

DanielRicany

Gotta put it on a lift. There's a fill plug on the side. Stick your pinky in there and reach downward with your pinky. If there's fluid on it then you're okay, if not, pump it to the unit until it comes out of the hole. Also see if you can see the cluster numbers with a pair of sun glasses

whalepirot

I suggest changing ALL fluids when buying a used car, especially in the O/D's ATF and filter. The two most common reasons they fail is lack of roper maintenance and misunderstanding how, exactly, they operate. Learn both and treat it accordingly.

I ran the excellent 4+3 for over 20 years,with little problem. The Doug Nash part, the O/D 2-speed "automatic", was more robust than the Super T-10 portion, in my case. I kept using it, rebuilt, when I installed my monster engine, mostly as insurance against the 500+ ft.lb. engine.

I ALWAYS (mostly) clutched O/D engagement/dis to unload the clutch packs. Know too, that O/D is not available, per the ECM, until the engine is in 'closed loop' operation. That is, unless someone rewired the car.

Do I like my modified car with the ZF6-40 and its .50 6th gear? Hell yes, but the conversion was neither cheap nor easy.

Oh, all GOOD Corvette drivers wave to each other!