[Hobbs64]

I'm looking for some input from the community regarding the ability to lock the Tcase in the E90's to a static torque split of 37/63 front to rear ala the first generation E30. The reason I ask is that it would open up endless options for engine swaps. I happen to want to use the E90 Tcase and transmission in my E30 project.

In the alternative, does anyone know of a separate controller available to control the torque split independent of the ecu?. I would like to look at un-marrying the functions if I can't lock the Tcase for a static split. Any input or thoughts are welcome!

[Hobbs64]

I have now done more reading and spoken with Jim at Kassel Performance, as well as some people who rebuild these Tcases. The Tcase is infinitely variable torque split via an actuator motor that tightens a clutch pack. Standard position is a 45/55 torques split front to back. At the same time the actuator motor in the Tcase is adjusting the clutch pack, and thus adjusting front to back torque bias, the ABS system is applying brake pressure the the slipping wheel for right to left bias on the axel. What all this means is that WE CAN INDEED MANUALLY CONTROL THE THE TORQUE SPLIT.

I may lock the Tcase down at a specific value for use in my e30 for the moment, but I'm going to try to get Jim to help me build a control interface for use in E90's by unmarrying the idrive function from the engine control unit. If this can be accomplished, all kinds of engine swaps become an option. In addition we should at some point be able to temporarily (and safely) turn off idrive and have a RWD drive car on demand. Any thoughts?

[BLKSAPPE92]

Read the article cause it interested me. I don't know enough about bmw transfer cases and multi plate clutch system. But by not changing internals and gears that give it automatic 45/55 split.

Wouldn't you be decreasing the service interval and be putting more stress on the actuator/pump and multi clutch. Say you wanna drive in rwd all summer those systems will be engaged all summer wearing the clutch and running the actuator to hold it in that position cause it's not the natural position till you change computer settings back in winter but I may be over thinking things plus it might need to operate brakes to achieve that.

I think the only way to get a true 0/100 or 100/0 or anything in between without wear would be if bmw removed the transfer case and drive shaft and used and electric motor to put power to front wheels but I'm probably over thinking this cause I don't know much about multi clutch systems in tcase or lsd but I though anything other then factory settings is causing wear why it only changes when wheels slipping is present and goes back to factory once all is under control

[rothwem]

The transfer case defaults to 100% rwd when there's no power applied to the actuator. Try it yourself and unplug the actuator, you'll be able to chirp the back wheels easily. The connection to the rear wheels is solid.

As far as making the torque split static, I would think you'd run into issues at the times where the computer normally uncouples in daily driving. The biggest example I can think of is when you turn tightly in a parking lot--the t-case uncouples to take torque off the front axles when you're turning so it doesn't stress the transfer case. I'm not sure if you've ever driven a 4wd truck in 4wd on the road, but you get a lot of binding, tire chirp and uglyness until the transfer case pops.

I think to make it full independent of the ECU, you'd have to have some control logic written to decouple it at certain times, or somehow try to wedge a differential into the spot where the transfer case is so that the front and rear shafts can spin at different speeds like a Subaru.

[TemjinX2]

based on what rothem said. Cheapest and easiest way, would probably rig a relay and switch to the actuator. That way if you want rwd only only, turn the switch off and if you want to go back to stock, just turn the switch back on.