The Btr 4 Speed Auto Thread.

[razbagz]

Ok, so what im leaning towards in regards to mods vs power; we can say if you are not murderous on your car everyday upto 240rwkw should be fine with a well serviced standard btr, this power is typically achievable with a good custom tune and CAI. For an extra safety net, add a transmission cooler(around $200), this should be safe for a little more power... say 250+rwkw e.g full exhaust, CAI, and tune.

The above seems like the typical "stage one" tune for the T. For us BA T owners its starts getting a little more expensive to go further safely and getting into the "stage two" tune territory, this would require valve springs, cooler,strengthened box, fuel system, more boost etc.

Edited 21/12/10 03:43 PM by razbagz

[Headsex]

The aim of this thread is to compile an information factsheet and experience register on the 4 speed that graces the early XR6Ts.Ill start with a few Qs that hopefully can be easily answered:

What are the telltale signs of a tired 4 speed?

Flaring 2nd(and 4th) and/or 3rd(and 4th)

What transmission oil should I use?

Standard specification should be fine of any brand type.

What power (on avg.) can this box handle? I dont mean the one that broke standard, or the freak that held up to do 10's. An agreed power figure would be nice.

Seen 250rwkw break one..

but, its a rather silly question.

Traction breaks these boxes.. The less power you have, the more traction you have, the more strain it puts on the box.

So a 400rwkw monster© "*Beep*" will wheelspin its head off, not putting any load on the drivetrain.

A 250rwkw car will not be wheelspinning, yet causing enough load on the drivetrain to train things like the planterys, which seems to break

But also in saying that, a Bad tuner can make a box last 10 minutes.

How and why does a transmission cooler extend and increase longevity of 4 speeds in regards to handling extra power?

Keeps the oil cooler, which keeps the oil pressure high to keep shifts in order.

When a rebuild is in order, what modifications and how much should I be looking at on average?

My box is a standard rebuild.. Ie, Standard frictions.. When people say they got "kevlar" frictions put in, I laugh, they are Hi energy/kevlar frictions standard.

My box also has a Servo for the band, But realistically, one is not required unless you produce a sh*t load of power. I've still managed to wipe my band clean (shifting to 4th in a power skid)

My box also has fairly extensive valvebody modifications, Which is the real secret to these boxes.

Most of the modifications are around the BAR and CAR hydraulic circuit, which is the BAND(/Clutch) Apply regulator.

I've seen modifications to remove the bias feed to the back of these circuits, which as a PRO allows maximum pressure, however with a CON of Maximum pressure 100% of the time, and NO PCM controllability.

Not recommended, however a lot of auto shops do this.

Another method is to change the multiplication ratio of the BAR/CAR circuits, which is done via a spring (welcome back to the old school way of shift kitting a auto).

Pro's of this method is to allow a wider range of control from the PCM(ie, higher pressure to the band/clutch), however, the CONs of this is if your tuner is sh*t, you can still burn the auto out.

Bayswater autos do the second method. And you need to rely on your tuner getting the auto shifting right. If you go back to Bayswater automatics with dead frictions in a newly built auto, be prepared to get your tuner embarrassed as they have HP TUNERS and can read and verify if the auto settings are the cause of the failure.

Bayswater automatics also open up a number of restriction in the valvebody to improve flow to the Band and clutch apply circuits, essentially the end goal is to get maximum clamp on the Band, to stop loosing 2nd/4th gear, and excessive wear on the C1 clutch (3rd/4th gear)

Mine also has a AU oil pump setup, which requires your convertor nose be changed to a AU type. Main point of this is the BA oil pump no longer have a bush to support the front of the internals of the auto.

If I was to take my car to the dragstrip, should I use tiptronic to improve my time? and is it fine to stall it up at the tree with generally no ill effects?

I drive mine manually, Only for 1 reason, to hold 3rd gear crossing the line. If I left it in auto, it attempts to shift 4th gear, which is bad for the auto with high power. It just CANNOT handle it.

But in saying that. it also depends on your tuner. You can command different pressure in Drive, vs sequential mode.

Edited 22/12/10 01:17 AM by Headsex

[Headsex]

you can buy electronic shift kits for them there are 3 stages from Shiftkits.com.au

there's not alot you can do to them,bigger aftermarket transcooler, fit au pump, clutches, cryogenic the hard parts, billet servo

Why waste your money on those electronic shift kits when you can do the same via the tune in these cars.

People do vary the clutches they fit, but realistically the factory ones is all mine has. its good enough.

Cryogenic the parts do help, but you can still break the plantery's.

Billet servo necessarily required, but helps with bigger power, but is known to break the band. Where some shops even weld the band to increase its strength.

[Headsex]

IMO the best way to increase the life of this box is to disconnect the S3 and S4 solenoids so that the box shifts hard. The so called shift kit by playing with the S5 solenoid is not the way to get everything shifting as hard as possible and doing it thru the tune isn't either. I have detailed this mod previously so not going to explain it in detail again. If you are really electronic literate you can get this mod to work just under load so that soft shifting during normal driving and hard under load.

S3 and S4 are associated to the BAR and CAR circuits, which are controlled via the S5 solenoid.

The S5 does not produce enough pressure alone to get the S5 line high enough for the BAR/CAR circuits. So this is why the Electronic shift kits fail. It will give you a tiny increase, but not enough as turbotrana explains.

The BAR and CAR circuits essentially do all the work controlling the shift pressure. Internally have a spring which multiplies the oil pressure ratio higher based off the S5 line. So the S5 line is basically the PCM controlled line pressure, but depending on what "ratio" springs the BAR and CAR circuits contain, that's what really drives your pressure higher.

So yes, your wasting your time with one of those electronic shift kits.

[bjcrown]

So it seems an external tranny cooler is the way to go.

I dare say it is to bypass the stock one.

Can someone please advise the size required (for say a tuned 245rwkw car)?

Thanks,

[xr6t_ute]

By "full manualised auto" do you use sports mode or still change old school?

I change old school

[Headsex]

in saying that, you've never "down-shifted" to use engine braking.

when the car comes to a stop, it automatically selects 1st gear again.

[turbotrana]

The S3, S4 and S5 solenoids are all there to provide soft shifting for the girls. By shutting off the S3 and S4 you render the

S5 redundant and it maintains full line pressure to the bands and clutchs. Fluids are going directly to the bands and cluches instead of bypassing through these solenoids which gives extremely firm shifting.

You dont need to modify the box internals, you dont need to drop the pan, you just need to disconnect the solenoids and trick the ECU into thinking the solenoids are still there by putting a couple of resistors to ground. It is so simple and cheap and works great.

Yet people are still talking about external oil coolers to save their box, different oils, electronic shift kits which are nothing compared to this mod. Its all about getting the box to shift hard and fast under load which makes it survive more than anything else. Yet I find this mod so overlooked but the guys who do try it find its a great bang for you buck mod.

Its similar to what Headsex said above"" I've seen modifications to remove the bias feed to the back of these circuits, which as a PRO allows maximum pressure, however with a CON of Maximum pressure 100% of the time, and NO PCM controllability.

Not recommended, however a lot of auto shops do this.""

Whilst I am no pro box builder, I personally do not want any PCM controllability on the BTR for performance purposes as IMO its the soft shifting circuits in this box that stuff it up in the first place so just get rid of them.

[XR64LT]

Before I started modding my BA T, my mechanic gave the transmission a service (oil, filters etc).

Power was at 256rwkw at first for about 5months and was fine.

Few more mods went to 302rwkw for another 5 months, still fine.

Fitted surge tank and new tune to 328rwkw, lasted 5 days, flaring in 2nd and 3rd. Surprised me as I was driving normally too.

Now rebuilt by CAT (Central automotive transmissions) with aftermarket clutches, bands, valve body and AU pump and 2700 TCI convertor and taking 348rwkw, hasnt missed a beat. Although I must say this is not my everyday car, would be lucky to get driven twice a week.

Leo

[Headsex]

Whilst I am no pro box builder, I personally do not want any PCM controllability on the BTR for performance purposes as IMO its the soft shifting circuits in this box that stuff it up in the first place so just get rid of them.

I agree.. For the sake of how many tuners that don't have a understanding on how to control the auto properly =)

But me on the other hand? I know how to, and the longevity I get with my frictions would be the proof in the pudding.