andy-gts

any Ideas as to why our torque converters are made to non lock up in 3rd or 4th gears.
Is it to protect input shaft from snapping?

andy

IcemanG17

How does the torque converter determine this...there is no "input" to it other than fluid?

blown 87

$$ that Porsche did not want to spend to redesign the transmission, there is a lot more to it than just sticking a locking converter in the car.
I also think the transmissions would not have the reputation of being bullet prof like they do if they have had a locking TC, seems to be a weak point with other makes as far as the lock up.
Lots of cars "Hunt" at some speeds and throttle positions.

WallyP

Smoothness and power were higher priority than fuel economy.

Remember that the torque converter is not just a fluid coupling that slips. When you put power in against resistance, the converter actually acts like continuously-variable gearing, with a max reduction of about two-to-one. A locked converter has no cushioning and no torque multiplication.

dr bob

Consider that lock-up converters didn't exist when the car/transmission was designed. Lock-up controls are integrated with engine load management software, so the same controls also manage what gear the trans is actuallly driving, what the actual road speed is, and other considerations like fluid temp, calculated engine load, throttle position, etc. Most of these signals are not available to existing engine controls, much less to a transmission 'brain'. Plus, there's hardly anyplace they could have put another controller in the car...

It would be nice to have a converter that locks in gears 4 and 5, with a hefty 1.2 overdrive in that top gear that isn't there yet.

At some poin in the car's development, the box currently offered in the Panamere will get grafted into a 928. The first conversion will likely be into a race car, where the ease of tub modification will make at least the initial fitment practical. It's just a matter of time before the Panamere box is cheaper than the unobtainium 928 fifth-gear/input shaft.

IcemanG17

Is the panamera a transaxle?

Another option is the later electronically controlled Mercedes 5 speed unit that is still used in the the twin turbo AMG V12's.....I saw them side by side with my automatic...and the transmission itself (torque converter housing back to where the diff mounts) looked fairly close in size to ours...just a tad longer for the 5th gear..which is a .86 overdrive anyway..... I asked the transmission shop that rebuilt mine how hard it would be to install the 5 speed....they said "hard".......but it could be done and would hold up to 850ftlbs continuous vs 500ftlbs for the 722 we have

blown 87

But in the end, you would still have a automatic.

Steve Cattaneo

It will cost Thousands $$$$$$$$$$$$$$$$$$$$ for a 722.6 conversion,

andy-gts

ball park number for thousands?

IcemanG17

Thats what I was told too...but for guys with big power strokers....I think it is worth looking into (PM Andy).....

Since what is their other options.....race guys can get a sequential...thats about $30k....and probably would suck on the street......

IcemanG17

EXACTLY.....I like knowing I have the stronger, less troublesome of two!!!

I've said it before & I will say it again, I DO NOT think the automatic is any slower on track..... I am 100% sure my Estate can keep up with any 5 speed Race 928 with similar power-weight.....

Steve Cattaneo

Let’s start with the transmission case, 928 transmissions are transaxles, differential and transmission components are combined into one assembly. On a 928 transmission the differential pinion gear is bolted to the transmission output shaft, and held in place by a nut and plate that’s between the differential case and transmission case. MB 722.6 Transmission cases are a one piece design and do not have a bolt on tail like the A28 has. The A28 differential pinion gear will not bolt onto a 722.6 transmission out put shaft. One would need to be made.

722.6 bell housings are bigger than the A28 transmission housing, here too bell housing would have to be casted to fit, and an adapter plate will not work, because it would push the transmission to the rear and out of aliment with other mounting components. The torque converter is also an issue, the input shaft on a 722.6 transmission is larger then an A28 input shaft, the A28 torque converter and will not fit onto a 722.6 input shaft.





MB Lock up Torque Convertors, use a PWM signal to lock the clutch on in all Forward gears,
An incorrect signal or wrong torque converter will put the transmission in LIMP MODE

MB Transmission Control modules are VIN coded to the vehicles, Engine, Transmission and
Differential ratio. If any is incorrect the transmission will default to limp mode. The Porsche Engine Control module will not work with this conversion

722.6 Transmissions are electronically control, by a Transmission Control module and are CAN connected to other modules and sensors in the vehicle and needs the correct input signal from the following control sensors Transmission range sensor (P R N D 4 3 2 1) which is a control module in the shifter housing and the fallowing components:

ABS module, signal
Wheel speed Sensor signal
Engine RPM Sensor signal
1\2 / 4/5 Shift Solenoids signal
2/3 shift Solenoid signal
3 /4 Shift Solenoid signal
Torque converter PWM Signal
Shift pressure solenoid signal
Solenoid valve voltage supply signal
Transmission RPM Sensor N2 signal
Transmission RPM sensor N3 signal
Accelerator Pedal position Sensor signal
Engine Torque input. Signal.

IcemanG17

SO clearly it would be a COMPLICATED project.....better off with a strong as possible 722.3.....

Steve Cattaneo

The 722.3 transmission in these vehicles can handle the torque, with no catastrophic failure.

andy-gts

so with our torque converters not locking up it actually saves the sudden application of power to the transmission and potential failure in high torque applicaitons.