ok so its kind of a stupid question, but does the 4+3 set up come both in an automatic and a standard? How does it work? i would imagine cars set up with this are much faster then without?

 

The 4+3 is a stick trans with a two speed mini-powerglide bolted on the back of it.
It is basically two transmissions in one.
it has a low gear ratio capability, and a high ratio capability.
In the low range, it is a normal 4 speed.
In the high range, it is basically an intermitant 5 speed, giving you overdrive....
You can always use any of the 4 speed gears, and the computer chooses whether or not to make that gear overdriven by shifting the powerglide, thus giving you 7 speeds (4+3)
The powerglide shifting is mainly taken care of by the engine computer uess you floor it, and then it unshifts out of high range, and you get your 4 speed back.
I have made mine a manual shifter, and removed the computer controls from it.
Essentially, I have a 4 speed trans, and I can flip a switch, making the powerglide portion shift. Then whatever gear I choose, I can use the 4 speed gear of choice with the aid of the powerglide to make it a higher 4 speed gear.
Essentially, you have 1st, 2nd, 2nd overdrive, 3rd, 3rd overdrive, 4th, and 4th overdrive.
You could actually shift like that, but the overdrive lowers the cruising speed of each gear to a ratio close to that of the next gear.
For instance, in heavy traffic, where the speed varies between 30 and 40, i might chose to use 2nd overdrive, or basic 3rd. There's only 200 RPM difference between 2nd overdrive, and basic 3rd. So if there are no hills, I would use the one that gives me 200 RPM better engine speed for gas mileage.
If I am on the freeway, and doing 55-60, i would be in overdrive, and shift between 3rd and 4th a lot.
On the freeway, if I'm doing 75, I am in 4th, with overdrive switch on, and taching 1800RPM.
without the overdrive, I would be doing 3000 RPM.
The corvette stickshift between 84-88 is the 4+3. Since the cars didn't come with an auto 4+3 , they came with the 700R4, and it is a 4 speed auto.
The top speed on both is around 150.

 

so assuming on a stock 4+3 equipped car can u rip through the gears lke 1st, 2nd, 2nd od, 3rd, 3rd od, 4th, 4th od like on a quarter miletrack? It sounds like a sick concept, i would imagine a 4+3 car would accelerate way stronger then one without?? almost like an f1 gear box where u dont get much of a drop between gears.........anybody ever time thier 4+3?

 

No, it won't work like that.
The 4+3 wasn't designed for drag racing. It was designed for fuel mileage.

If your going to drag race, just use the 4-speed like any other old school 4-speed equipped car.

The +3 part is an automatic overdrive added to the back of the trans, and would probably slow your 1/4 times down considerably.
By the time you got done shifting in and out of OD for each gear, the race would be long over.

 

This is probably the best description of it I ever read here. I too have the 4+3. After you go through the first 4 gears, you just push the O/D button while pushing in the clutch and the car then goes into overdrive. It's used by most as a 5th gear and gives the car a top end of about 150mph. I had mine to 147 with no problem on an abandoned highway. As said before in the other post, the first 4 gears can be used as normal if you want. It's a strong T-10 4 speed transmission that works very well on 1/8 or 1/4mile track.

 

I recently posted this on another forum. It may be useful to folks here considering a 4+3 car.

I've been driving my 86 with the 4+3 as a daily driver for 3 years now (it has 86k miles). I actually think having 2 sets of 4 gears (1 set for performance and set 2 for better economy(OD)) is kinda nice. OD engages automatically when using light throttle pressures in 2nd, 3rd and 4th, as long as the engine temp is 120 degrees or greater. You can also force shifting in and out of OD with the button. I generally use the clutch when I shift intentionally in or out of OD. It is just a whole lot smoother that way and easier on the OD unit I think. I like to shift, so I don't mind this.

I cannot complain about the automatic shifting of the OD except when it drops out of OD in 2nd gear when too much throttle is applied (intensionally or not) the car launches pretty briskly and my wife gets pissed at me....LOL. She hates speed! I try not to do that when she is in the car. It can also happen in 3rd or 4th gears when you apply a little too much throttle (say on a hill and you want to accelerate a little).

I have no apparent mechanical issues with my OD unit, but I think my 4 speed gear box needs some work. It will pop out of 2nd when compression breaking in 2nd gear. If I avoid down shifting to brake in 2nd I have no big issues with it. It also seems there is drive line play in my unit when you go off the throttle at low speeds (say idling through the neighborhood at 10-15 mph). I have no way of knowing if the play is in the OD or in the gear box.

Don't be fooled into thinking you are going to have 7 gears. It's not like driving a truck with a gear splitter at all. The reason I say this is the ratios the designers have chosen. The ratio of 2nd gear with OD engaged is very close to 3rd gear W/O OD. The same is true for 3rd with OD and 4th W/O OD. Those ratios are very close also.

If all the 4+3 shifters feel the same as mine, then this is an area where GM does not score well with this design. You won't be speed shifting this guy. It is less than smooth in transition between gears. It does not grind or anything. It just feels rough as you slide it from gear to gear (both directions).

Maybe this will help somewhat in understanding how the DNE 4+3 feels/drives for those who have not driven it. Hopefully so!

Tom

PS: Another owner posted that the Super T10 4-speed component of this design will never shift like a modern internal rail design because it has external linkage and the linkage and shifter are more subject to wear. He also stated that the T10 was used in many of the 60s Muscle Cars. If you are familiar with that driving experience, this may be similar.

 

and are they geard (rear end) the same way as a non 4+3?

 

The 4+3 will have the Dana 44 rear with 3.07 gears. Great for highway and still great for torque.

 

Didn't the 4+3 84 come with a D36?

 

Yes, in 1984 the only option was D36 (both automatic and 4+3 manual)
Note: The 4+3 wasn't available in the '84 until January, 1984

The D44 was released for the 1985 models, and only for manual transmissions.

 

If that's the case, hypothetically, a C4 swapping from auto to a 4+3 could use the 1984 C beam out of a manual trans car? I've wondered about that.

 

The 4x3 is only clunky when it is worn out.

When I rebuilt mine, the shifting was much improved.....

 

That's real good to here from another owner! I assume you are talking about a rebuild of the 4 speed. I cannot see how rebuilding the OD unit would improve the manual shift of the transmission, correct? I have been thinking about ceasing this opportunity to try rebuilding a manual trans myself.

 

You only change beam when you change diff ; not trans
An '84 man C beam is the same as any D36 auto beam.Beam length is determined by diff ; not trans type

 

Obviously rebuilding a 20 yo trans is going to improve it but you can't go past the fact that all external linkage trans are clunky compared to smooth shifting late model internal rail type trans.
Best mod you can do on a 4+3 is install the short shift kit

 

And a pistol grip

 

Understood, but let's be blunt here......people get in a ~20 car and judge the transmission by how it shifts.....and the inspection plates haven't been removed in that same ~20 years.

Again, being blunt, get a fresh rebuild on that thing and then tell me how it shifts.

Mine was much nicer...but before I [Had] it rebuilt, I just chalked up what I was feeling to the group think that they all shift horribly....

It's all relative isn't it? So folks are running around with a tranny that needs to be rebuilt....but since all they heard was that it was "clunky" and theirs is clunky like everyone described.......so leave it be and save up money for a Tremec..........

First address the ~20 year old component and then come in here and describe what you feel now versus how it felt prior......

 

Lemme be clear, I'm not stating that mine is smooth like butter.....I'm just saying that it is better than before.

 

Man I like that! I guess it's just screwed on where the original was? Cost?

 

Thanks.....its one of my favorite things I have done to my car. I also have the short throw kit. It fits your hand perfect when your forearm is on the console. The thread adapters are all the wrong size, i just drilled out the threads on the handle and it "self tapped" itself when I screwed it to the shifter. It was about 45 bucks at Autozone. They also make this with the button on it.....I kinda wished I would have got that one, but I like the clean, buttonless look. Cheap and easy.