PSIG wrote: ↑Mon Sep 13, 2021 9:23 am
blackbird wrote: ↑Mon Sep 13, 2021 1:39 amFor your 4l70e the 4l60-70 family is pretty scary to deal with. The 3-4 clutch vs the band is just a terrible design. Lots of issues in those things... Plenty of better newer and older trans to work with. That being said, what exactly are you attempting to do with it? Maybe time for a new thread, but I'm curious what you're attempting.
I'm just after simple control of the 2009+ 4L70E, 4 forward gears and lockup, programmable auto-shift. I'm only familiar with sisters such as the 4L60 and 80, and don't really know what's different in control of the 70. A bit of an orphaned oddball.
That said, it shouldn't be too tough, but without a working example here to test signals, I don't know the specific sequencing or how it's different than the common 4L60. No option to swap for another trans. Any info to get a auto-shift going on one would be very helpful. AFAIK, there is only one active commercial controller out there that even tries to handle the 2009+ 4L70E, so there is a small but eager bunch of potential users.
A 4l70 or 60 is pretty similar. I know there are some internal hard part differences, but the 70 hasn't quite solved the core issue of the transmission. If you ever plan on exceeding maybe 450whp I would flat out go a different route. They "can" hold 600whp or more depending on vehicle weight. But, some of those transmissions are basically never driven on the street, and will get rebuilt far more often than other solutions out there. And once you get into a billet converter (which I think is sort of mandatory if you plan on making power, and want it to last with a lock up), and built trans, you're spending very much the same money as just a better transmission that's been built. I guarantee you there are solutions that don't need much work at all that will take a lot more power, for less than a built 4l60. And will give you the benefits of an efficient transmission. The controller opens a lot of doors in that regard.
The terminator X Max, and Holley Dominators have 4l70 control built in. There isn't really any electronic solenoid trick that is specific to that transmission, beyond understanding a few basic ideas. As in there isn't much you need to worry about slipping or partial filling.
What is critical is that the 3-4 drum has A LOT of preload springs. The preload springs act similar to a wave plate, and cushion the apply. The Band is on, and releases as the 3-4 drum applies. Which means the band also needs to be not too tight, nor too loose. If the band is too slow or sticks too much, the 3-4 drum will apply and not be able to overcome the huge surface area and total friction of a dragging or slow releasing band.
This is probably the biggest issue in the 4l70 4l60 700r4 etc. You really can't have that clutch pack setup to have maximum hold, nor maximum apply rate. You really need to delay the application as much as possible to allow that band to release. Borg Warner High Energy factory clutches should exclusively be used in that 3-4 position as a result. The fibers allow fluid to flow through the clutch material even once the pack is applied. Borg Warner truly is lightyears ahead of the aftermarket in terms of clutch paper technology and application. Only the GPZ one sided pack can compare, but for the price difference it's honestly not worth it.
There are some other little tricks you can do to help this apply the way you want, send me a PM if you'd like to know more.
In terms of strategy electronically, you need that pack to apply late, but obviously not too late. I believe (although to be fair I really don't look through anything about these transmissions at all, I wrote them off personally), the 4l70 has pillow switches. These would be very very useful to have integrated as an initial condition to trigger a solenoid activation for 4th gear. Look for the pressure to drop in the band circuit to increase apply pressure. You may want to also have apply pressure ramp in/stagger the pressure increase. This also gets into fluid choice, which will matter. As well as steel separator choice etc.
Then super critical is setting up a good torque management profile. You want to cut power just before the shift, all the way until the shift is completed. This will help a lot. But can be tricky to do. Some engine setups will be fine for all situations just pulling out a few degrees or even a lot of timing for this period. Others it can cause drivability issues, and you really would want a throttle closure (use of DBW). Some cars a throttle closure will make it drive like garbage, where as a few degrees of timing would significantly drop the crank torque. So that's really up to you to figure out, but it's going to make a hell of a difference. So some kind of output signal when it should be active, how aggressive it should be, and whatever variations needed for the ECM to be able to adjust. IE if the car is in high load midrange rpm, you treat that differently in terms of timing cut amount or throttle closure to a WOT high rpm situation. Or low load mid/low rpm etc.
Finally line pressure. Line pressure is a funny one. Some situations higher line pressure will actually result in less clutch wear, others it will increase clutch wear. Generally I believe in following boost/air flow to decide how much line pressure to use. The exception is for some boosted performance setups where you might leave at a low boost for example.
The valve body is pretty critical for this application, and that's something I really can't shed much light on (each valve body is it's own deal). Precision Transmission on YouTube definitely has plenty of info about these trans and I would recommend looking at their videos for an idea.
Then you want to look at how each trans comes together (as most will be "upgraded" or modified) and how each part works/changes the effective apply rates/pressures.
Sad, as I was watching to pull crossover info for a 4L70E project, but it is what it is.
- By MarcoRosi