Auto Mods For Big Hp

[GTSBoy]

Well, yeah.....the clutch in the converter.

[steve200b]

I will let you know in a few weeks for sure

[sonicz]

Well, yeah.....the clutch in the converter.

Hi. I'm having a problem with my stock rb25det auto box slipping. I am 99.9% sure the culprit it worn out burned out clutch plates. Are you saying If I simply swap out the torque converter and keep my box I will have a fresh set of clutch plates?

This is good news if that is the case.

[GTSBoy]

No. I was saying that there is a clutch in the converter that does the locking of which he was speaking.

An auto trans is absolutely full of clutches. There's pretty much one for every gear.

[scotty nm35]

There are 5 or 6 clutch plates for each gear, and steel plates between them. (Like a motorbike clutch pack.) The clutch plates only have 0.5mm of material on them so when they slip it doesn't take much to wear them to metal requiring a rebuild.

They have in excess of 200psi oil pressure pushing the pack together when locked so there is massive heat generated if slipping occurs, more than enough to warp the metal plates between the clutches. If you get the box rebuilt they will usually toss the lot and laser cut some thinner metal plates, to allow extra clutches to be installed in each gear's clutch pack. That way it can hold more power.

[sonicz]

There are 5 or 6 clutch plates for each gear, and steel plates between them. (Like a motorbike clutch pack.) The clutch plates only have 0.5mm of material on them so when they slip it doesn't take much to wear them to metal requiring a rebuild.

They have in excess of 200psi oil pressure pushing the pack together when locked so there is massive heat generated if slipping occurs, more than enough to warp the metal plates between the clutches. If you get the box rebuilt they will usually toss the lot and laser cut some thinner metal plates, to allow extra clutches to be installed in each gear's clutch pack. That way it can hold more power.

That still doesnt answer if the cltuch plates are in the torque convert or the inside of the transmission.

[scotty nm35]

GTSboy answered that. There is a single plate lockup clutch in the torque converter, it's job is to obviously lock up the torque converter, to make it direct drive, like a manual clutch.

There are also many clutches in the gearbox for the gears, and a band (like a drum brake) to slow the car when you back off. If yours is revving right out on slip it will be the gear clutch which has worn. If it only revs out onto the stall converter speed, it will be the lockup clutch that is faulty.

[sonicz]

My bad. Well while we're on the topic. Its Difficult to address what you raised unless you know exactly what I mean. The car is not revving out at all. In fact it begins to stall and shifts like a brand new box. The problem is there isn't a direct engagement between the Engine and wheels like there should be under WOT, or even 1/4 throttle sometimes. I am not talking about the first few seconds or pulling out of the driveway.

After a certain point when pressing the accelerator the car stops continuing to accelerate and starts to shudder back and forth a bit. By this I mean the increasing rate of acceleration as engine RPM rises, halts. The car obviously still picks up speed in this state, but it would look like the powerband has flattened out on a dyno at 3000rpm but its not due to lack of power from the engine doing it. I hope you get what I mean by all this.

In addition, I think the ECU backs of timing or lessens power output depending on the state of the transmission and even when the clutch it slipping. I can also feel it cutting power in between shifts. This is normal, but it seems to confuse people to think the transmission works and sfhits normally, whereas I can easily detect when there isn't direct engagement. Its like if you held the clutch at 3/4 lock in a manual car and as soon as you felt slip backed of the throttle and kept it there. Its not right.

Edited October 1, 2013 by sonicz

[scotty nm35]

Sounds like what a torque converter should be doing. It should unlock as you accelerate and lock again once you are cruising, allowing the engine revs to rise onto stall when you boot it. Perhaps you have a high stall converter fitted already which may make it seem worse than usual?

Yes, the stock ecu mapping backs out timing between shifts.

[sonicz]

I'm not that familiar with the inner workings of an AT. What I do know is I can feel G forces in a car, and what is happening increasing acceleration it halted somewhere down line of the engine. I dont think its normal for at transmission to be the limiting factor on acceleration.

The following is a good anlogy of what i mean by direct enagement, Its kind of like wheel spin. When your wheels are not loosing traction, you have direct engagement with the road, but if you exceed a certain point and your wheels begin to slip, no matter how much HP your engine puts out, your acceleration will be limited. Solution is to get more grip on the tyres, not giving the engine more HP. The same thing is happening here.

Ive owned a few 300HP+ AT cars. I know in my mazda (200,000ks+ and previous owner never changed At fluid) I had the same problem. Mechanics said box works fine. they just drive it, checks if it shifts smoothly and that is all. Doh!

But I knew it wasnt. I was lucky enough to find a brand new box for $2000 during a mazda warehouse clearance and had it fitted. The car felt like it double the power. No more slip.

[Aldawy]

Does anyone know if the RE4RO1A auto that is behind the rb25det in the r33 (also behind 300zx non turbo)

Is this auto in any other skyline.

I've been looking on eBay at the autos that are in r32's & r31 series 3 ,the pictures that people have look like the same autos

Can any one confirm this is true

[steve200b]

From what I have found the series 3 r31 and r33 has the a series box and the r34 has the b series re box. The b series has more clutches and a stronger box.

[StevenCJR31]

Does anyone know if the RE4RO1A auto that is behind the rb25det in the r33 (also behind 300zx non turbo)

Is this auto in any other skyline.

I've been looking on eBay at the autos that are in r32's & r31 series 3 ,the pictures that people have look like the same autos

Can any one confirm this is true

The series 1 and series 2 R31 had the 4n71b. .series 3 31 +32 +33 are all re4ro1a

Series 1 R34 has the re4ro1B

Series 2 R34 has a different trans again afaik

[StevenCJR31]

The series 1 and series 2 R31 had the 4n71b. .series 3 31 +32 +33 are all re4ro1a

Series 1 R34 has the re4ro1B

Series 2 R34 has a different trans again afaik

The y31 cedric etc has a stronger re4ro3b

[Aldawy]

Thanks for all the info everyone

[Aldawy]

Has anyone connected a b&m shifter to one of these autos

I'm planing to make it 4 speed on the shifter instead of 3

[steve200b]

Has anyone connected a b&m shifter to one of these autos

I'm planing to make it 4 speed on the shifter instead of 3

4th gear is run of a switch when using a b+m shifter. If you are going to use a b+m shifter buy the correct brackets to make it work correctly

[Aldawy]

The person how is going to build the auto, does a manual valve body with 4 gears on the shifter & also can do a trans brake as well if I want

[steve200b]

From what I have found there was only one company doing a trans brake manual valve body but they went broke last year. All 4 speed jatco boxes have an electronic solenoid to engage 4th not activated through the selector

[Ben C34]

The person how is going to build the auto, does a manual valve body with 4 gears on the shifter & also can do a trans brake as well if I want

Can I ask who is building it and how much?