2vettefamily

I currently own a C6 (2013), had a C3 (75)sold it-looking to possibly purchase a C4 (84-88). Gotta have a stick, but I'm reading about way too many 4+3 nightmares! Best off staying away?? New to the forum>Thanks

AirForceOne!

Get an 89 with the ZF 6 speed if your worried. In 90 the interior changed quite a bit, you may look into that too!

mazdaverx7

its a matter of opinion really... the T10 4spd transmission is a rock solid transmission by any account. the weak link is the overdrive unit that's bolted onto the back of the trans. if it has not been service properly or has been abused then in the chances are higher that it will fail. in my opinion it is not wise to engage the overdrive switch when in motion without first depressing the clutch pedal. if this is not done i personally feel as though it can prematurely wear out the overdrive unit.

with that said, the ZF 6spd trans found on the later C4's is near bulletproof and does not have a weak link really. if anything is a weak link in that particular setup, i feel the dual mass flywheel would be that link. if the flywheel's rubber innards has gone bad there is no new dual mass flywheel available from GM. they don't commonly fail but when they do, finding a replacement can prove to be difficult.

there are pros and cons to both. i have personally owned both the 4+3 and the ZF 6spd. i do prefer the 6spd trans over the 4+3 but i cannot fault the Doug Nash 4+3 much either. as with any car its a gamble and it comes down to personal preference. i say go out and drive an example of each and decide what you prefer. the 4spd unit is really unique and is fun to drive in its own right. if i found an early C4 that i had to have, i would not hesitate one bit if the car had the 4+3. i would welcome it in fact.

FOURSPEEDVETTE

If you're reading a lot of negativity on them, figure about 90% of the comments come from people who have no clue and never owned one to begin with.

artvette

27 years and still happy with mine.

lkl2005

My 86 is a low miles car. 20 K but the 4+3 works flawlessly and I like it. It is a part of the corvette history and intend to treat it right and enjoy it the way it is.

redrose

inside the OD unit, the friction discs (rumored to be ford base) are too small for engage/disengage of the OD under load, use the clutch pedal to go in/out of OD and no problem...84/85 have a problem with early fail of the seal between the OD and the front (ST-10) case...computer control of OD is marginal, convert to manual switch for greatly improved operation and life

Little_Red_Corvette

My 85 has 15500 miles I changed the fluid in it and it too works great. Only weird thing on mine is the O/D engage switch is in the console next to the mirror adjust. I also don't disengage it until the car has slowed enough to dis-engage itself then I turn it off while driving around town.

1985 Corvette

It's an oddball trans but it is more misunderstood than all out disliked. Even the official description for the C4 drivetrain section under articles on this very website refers to it as a "Doug Nash mash up". Probably just a playful jab at it. I believe the electronics and the mystery of all the OD's operation patterns turns a lot off to getting involved with it.

I kick around the idea of doing a rebuild of an 85 unit I have with the hopes of providing a "how to" on a complete 4+3 overhaul from T10 to OD to shifter linkage. After figuring the costs of all the tools involved along with parts, I am pretty close to a low miles ZF with bellhousing by the time I was done.....

Anyone's 4+3 shifter linkage shift smooth? My shifter linkage is clunky...even when aligned. An old Motor Trend video from 1988 even mentioned the shifter was clunky and it looked it too when they rowed it through the gears. Gotta be a way around that clunky, notchy feel.

2vettefamily

Thanks for all your input. I guess it's like anything else. Treat it right and it will treat you the same!

milsurpman

I owned one in an 86 and it held abuse. But when my original engine went away with a boom, I tore down the overdrive unit as precautionary with my new build. I ran into the planetary carrier missing needles due to poor factory assy. My trans would probally of failed short order under the new power level. I searched high and low for a planetary bearing and ended up after 3 months buying a full carrier which was supposed to be the last one from darrels back in the day 1998. which back in the day carried all the 4+3 parts pretty much. If you have no hard parts problem your golden and its easy to rebuild but if you loose a hard part your screwXX. Other then the the parts problem I had, Its was a great trans and I loved it. JP

vetteoz

No trans with external linkages esp one designed in the '50's like the BW T10 that the 4 spd part of the 4+3 is based on,
is going to have the smooth shift of a internal rail trans like a ZF6 or T56

c4cruiser

I've had my '87 with a 4+3 for some 8 years now and never had a problem with the OD unit. The car sees a lot of autocross events and track days. To be fair, I don't use the OD unit at these events. Going in and out of OD at high RPM and high torque is not a good thing to do with it. The 4-speed is basically the same as the Borg-Warner Super T-10 and is rock solid.

As others say, the key is regular maintenance and don't abuse it. Change the filter and fluid every 12-15K miles or annually. It uses regular Dexron III ATF and the filter had be bought at parts stores (same filter as used in early 70's Ford FMX auto transmissions).

Driving around town at speeds like 45 or below, I usually don't use the OD although 3rd gear and OD is a good combo for 45-50MPH cruising.

The OEM shifter is sort of clunky and it bolts to the body, not to the 4-speed like the Hurst Competition Plus units that were popular on the muscle cars that used Super T-10's. Worn bushing are sometimes an issue but they should be available.

I think one of the questions down the road will be parts availability and experienced rebuilders. I had read that S-K Speed is getting out of the 4+3 business and they were selling off parts.

There is nothing wrong with the ZF 6-speed that came in the 89 and later C4's either. It's a good tranny and will handle a fair amount of HP in modded motors.

The early 4+3 cars can be retrofitted with either a ZF or Keisler has some 5-speeds that are available as a bolt-in replacement for the 84-87 cars. They can be pricey, but a straight forward install and the 5th gear is about the same ratio as the OD unit.

zr1fred

There's a very good reason people switch to the ZF or the Keisler. If you find a 4+3 that works flawlessly....great, but the newest ones are 25 years old. They've been a problem since they came out. I've had a lot of them, and worked on a lot of them. Choose very carefully.

Netfly

I've owned both and after a few days with the 6spd, the 4+3 becomes old fast. It was slower shifting, had a weaker clutch and the OD was a heavy, clunky bandaid to an old 4-spd. Drive both before you decide.

skybolt31

I had one in an 86 and it took a little getting used to but I had no issues with it. I used to drive it like it was a 5 speed, when stopped, hit the button to shut off the OD, go through the 4 speeds and then hit the button again to turn the OD back on.

What I didn't like is that it is an orphan transmission, only used on 84-88 corvettes. I did a lot of reading and there are very few people that know how to fix them. I drove my car from CT to Mt. Rushmore and had if failed while on the trip, I am not sure I know what I would have done. My 95 is a auto and serviceable almost anywhere. You might want to check out this site and give these people a call:

http://www.skspeed.com/corvette_transmission.aspx

QCVette

I have had two (an '85 with 0.67 OD & an '87 with 0.60 OD). I used them the same way. I used the OD like a 5th gear. I also used the clutch when I shifted in or out of OD. Never had a problem with the OD in either car.

That being said, I have had two ZF 6 speeds (both '94's), and I do like them better. They shift easier/smoother, and more ratios. I really like the 0.50 6th gear for good cruise mpg on the highway.

Joe Gibson

I have an 86 Convertible Corvette with the 4+3 and a 97 Camaro LT1 with the 6 spd; between the two I find the Corvette to be more playful and way more fun to drive.

This is my second Corvette and I spent 2 years looking for one in decent shape with the 4+3 and another 5 years tearing it down to bare metal and rebuilding her.

I love me the sound of a beefed up L98 as it drops into 4Low and tears off.

The Corvette makes me giggle like a lil girl every-time I climb into her for a drive.

Regardless of what you decide love on her and worship her and you will have fun.

On a side note: Keep in mind ALL CORVETTES are Dominatrix and sadistic; it's all about her Pleasure and Glory and your pain. If you are like the rest of us you will happily bow down and ask for more.

Rohn

My 1984 4+3 is 130K old. Still just fine. the overdrive leaks a bit. I depress clutch when I engage OD and it stays engaged during cruise and never forced out of OD and used only over 62 MPH over 1700 mph. My car is cammed so I lose TQ. A POI is that I datalog often and whether in or out of OD at that spot on 55-62 mph gas mileage is the same. I found this out as the wires to OD shorted to each other and for about 10 days I could not use OD and my logs showed same mileage on way to work.

blkvette85

Also 80K on my 85. Never any issues. Change the filter and fluid on a regular basis.