turbobuick33

I know the 85 - 88 vettes had the 4+3 manual trans. How good are these trans? And why is it call 4+3?

85 500 horse

My 85 HAD the 4+3 and now a Keisler 5-speed TKO-600 resides in there. The 4+3 acts like an automatic. It will automatically downshift to another gear depending what gear you're in. It can do this 3 times, hence the name 4+3. It's a 4 speed with 3 other gears that automatically shift.

They're prone to breakage, are finicky and expensive to repair.

ottawabarber

Here is a link to an older thread that is very informative. I love my 4+3

http://forums.corvetteforum.com/c4-g...-using-it.html

69427

That was my experience with the 4+3. I'm now running a Richmond 6spd.

zr1fred

Actually it's a 4speed trans with an overdrive on the back of it that works in the top 3 gears. It will shift in and out of overdrive manually or automatically. Most of them are "prone to breakage, are finicky, and all are expensive to repair". Kinda like the lottery, very few win, most lose.

jrzvette

It's a strong transmission, good enough to be installed in the Calloway Twin Turbo cars. But the overdrive unit (which is essentially an automatic) required more frequent servicing and fluid changes. Many owners neglected this and that unit is prone to failure. Hence the bad reputation.

tequilaboy

I've always been happy with mine. As of now, its configured more like a 3+2 in my 88, but is off by default.

I've modified the programming so that when OD is enabled its now very unlikely to upshift to OD in 2nd gear on drive off (unless the throttle was always below 5% in first gear prior the the shift).

It will upshift normally in 3rd gear (instead of 4th) after a 2.5 second delay, if also above 34 mph. I can drive normally 1st->2nd->3rd->3rd OD. I can always manually shift to 4th OD if desired.

For me, 3rd OD seems to be a better overall choice for normal driving below 60 mph.

The ratio drop from 3rd to 3rd OD and the 2.5 second delayed shift timing also feels pretty natural and is well suited for my current 3.73 gears.

I've experimented with just about every possible variation of the control logic, and I'm reasonably happy with the current arrangement.

xlr8nflorida

The thread should have said how bad are they?

FOURSPEEDVETTE

Just someone else who didn't know how to use it or take care of it.

RedVette84

I agree that the lack of fluid changes doomed many a OD. But another problem is the bearing in the OD that is lubed by the factory and can't be lubed again except if you take the OD out.

nassau66427

I had one in an '84 that I bought new and kept for about 6 years.

Other than having it replaced under warranty after about a year, I had no problems with it.

If you're unfamiliar with its operation, it'll scare the crap out of you when it automatically engages at 115 MPH.

DanZ51

I think you're referring to the front carrier bearing. It does get lubed but not enough for a healthy life. IIRC there was a Service Bulletin out years ago that mentioned drilling the carrier plate for an oil feed to the bearing. Replacement bearings came with a new carrier plate already drilled.

Combine this ball bearing (not tapered) with Doug Nash Engineering's poor assembly tolerances (some had too much lash, some had zero lash, some were preloaded ) you had a recipie for disaster.

Aurora40

As to how good they are, I think I'd put it like this: No one swaps a 4+3 into anything.

That said, I wouldn't shy away from a car with one if I liked the car and the trans worked properly.

KeislerSales

Well said.

redrose

wrong

4-3 is a couple inches longer than most other trans, needs fluid piping/cooler, no "std" rear mount, minimal tech savy for control scares newbs away.

have seen a few in "high end" rods.

4-3 is good, o/d clutch packs are marginal but "real" driver can avoid their short, "genius" that did ecm interplay was bad.

Aurora40

Let me take a guess: You have a 4+3

coupeguy2001

Well aurora, i swapped one into a 57 Chevy pickup, and it's manually engaged by a switch on the shfter, and manually disengaged through a switch on the clutch pedal. I love that thing.
My ol' pickup is a hoot to drive now. I concur with tequilaboy in that 3rd overdrive is an around town cruising gear.
I installed an 87 power steering cooler in line with a spin on oil filter adapter on the cooler lines, a K&N breather filter, and the thing seems real happy in the old hauler.
What's funny, is that sometimes I get paced by people that like my truck, and I ham it up by shifting about 7 times, and at stoplights I get questions like "is that a semi trans in there?" or "Geez dude, how many gears does that thing have?" or " is that one of those new 6 speed automatics?" or my favorite "Hey dude, pick a gear and stick with it" There's more, but those are the funniest.
I can't do burnouts as well since my old 4 speed had a lower first gear. The overdrive outweights shortening my rear tire life by offering 1800 RPM @75 mph in overdrive vs the 3400 RPM @ 75 mph before. Hey, now I can hear the radio on the freeway!!!!
I just have a ZZ4 hanging on the input shaft of the trans, 3.38:1 gears, but If I had more power, it would handle it.
See my "corvette photos" ....albums..."cars" for a pic of my '57

redrose

4-3 currently in the car...present 'weapon of choice'

"under the bench":
NOS 4-3 complete trans, dated 88.
super t-10, 2.43 first (complete good trans , poss gear change for 4-3).
chevy case NPG 4 speed, o/d in high gear (426 hemi torque capable ?).
t-5 W.C. from v-8 camo(future project liteweight 4-3 replacement).
t-5 with 4.00 first gear from s-10 4-banger (too cheap to pass by).
two complete muncies and parts enuf for at least two more (old gold).

researched zf 6-speeds and rejected same due to useless "second" overdrive, 1-4 gear ratios same (for all practical) as stock 4-3 and "wide" t-10 (why bother), torque rating same or less than other choices, parts and service unavailable locally...low, low price of NOS zf's is ?????

tk-600 looks interesting, 'feedback' limited.
richmomd has poor customer support history.
t-56 next on research list, rumors of headaches at install are discouraging...another useless 'second o/d' ???

Aurora40

I give. The world is divided into two types of people. Those with 4+3's, and those that wish they had 4+3's.

To the OP, if you find a 4+3 car for sale, buy it. Worst case if the car is junk, you can sell the 4+3 for big bucks to someone looking to upgrade their ride. Also, I apologize to you on behalf of all 4+3 owners for previously trying to answer your question honestly.

89er

Make sure it it '85 or newer. Then toss the 4+3 and you have a vette with a Dana 44.