Directions seen above for my new trans with trans brake.

It calls for tying into a wire on the stock harness for the pressure solenoid. No big deal.. it sounds like I will also have set no error reporting for code p0748. Is that all? Or does tuning need to be totally re-done for fixed pressures and such? Or is simply no error reporting the code enough?

 

Ugh! ... CK 4L80E Trans-Brake Valve-Bodies:


240 PSI?!?!

 

Yeah its a CK. I didn't choose it. Long story.

I guess my other question is why the hell do I have to tie into it 3 inches off the connector when I can do it right off the wire going to pcm instead (obviously not on the pcm side)? The harness is annoyingly short down under the car lol. Feel like it's just a signal wire... I should be able to do that. Thoughts?

So Does this thing need different tuning or can I just delete the code? It's already been tuned for the 4l80 within the the 4l60 software (pcm of nc harness )

 

I also don't give two $&>ts about using the trans brake. I just want reverse. Ffs...

 

Oh 1 more thing. I should add that this is a fully built 4l80 trans from a very reputable builder.

 

Personally, I hate fixed line pressure anything. and unless the trans was built specifically for the transbrake why not just go to a stock or performance modifed valvebody if you doing care about the brake. In face most including the CK brake require multiple internal mods be done they are not simple bolt on. Was the unit built specifically for the transbrake?

 

Yup the trans was built specifically and all proper mods have been done. It is someone else's build for a 1200+ HP car and he changed plans. I got it for a great deal.

I will use the trans brake someday, but for right now, I want the CAR TO MOVE. It's been down for months lol

 

it just says minimum of 3". the way id do it is pull the pin out of the ecm connector and tie in there.
with that said, i think you should keep the epc solenoid functional. many pros will say they see lots of burned up 80s as a result of the epc but thats from bad/neglected tune and they like to see fixed line pressure to eliminate that variable. understandable from their perspective.

just delete the code. when you unplug the epc solenoid it defaults to max line pressure.
as long as youre digging around in the tune anyway, why not do a proper segment swap so you can get rid of those inverting relays? or better yet, sell the transbrake and install a stock valve body while youre at it.

 

I will delete the code.
The PCM of NC harness is, in my opinion, the superior way to do the swap. The trans will lock and unlock the converter using the 60e software. Which is much more pleasant than the 4l80 software. Overall drivability will be a better experience using their harness and no segment swap BS is needed. I was doing some more reading and the valve body has its own pressure solenoid.
I dont think it'll be an issue.

 

Tied into the wire up by the pcm instead of the harness under the car. Much better and easier to work with. Going to a stock valve body isn't in the cards. As I will use the trans brake some day. For now I just wanted to drive the car after being down for months.

Trans works flawlessly and we're up and running again. Thanks for the assistance.

 

Glad you got it going.

 

Don't listen to the haters. This brake works very well. If you want to keep the variable line pressure (I don't recommend for turbo applications) , wire in a relay that open the epc circuit during brake activation.

 

I won't listen to the haters. A very reputable builder put this together. He's not going to put cheap garbage in it. Very happy thus far

 

Who's the builder?
And the brake has a couple different versions from CK
Is this the version that uses a detent solenoid, or the version that uses a "nitrous" type solenoid? They behave differently

 

are you doing that with PR spring or full/fixed via the boost valve mod?

I have been drilling the epc plug with the modded boost valve like you were doing awhile ago. I went to .050 and it idled (750 rpm) hot at around 40psi which is not quite enough to engage reverse to come up onto the brake. my solution at the time was to just foot brake into the first bulb, engage the brake and then bump in from there.

seems like a custom holley table could control the epc relay.

 

Why would a transbrake need 220 PSI - 240 PSI in a low power application? Guys are running trans brake setups with 1000 hp with 180-190 PSI fixed line just fine.

My last two builds I saw 210 PSI in and 180 PSI in the other. Both are built exactly the same with a .040 hole drilled in an EPC plug with a TB VB electronic shift that kills reverse boost. All new GM parts unmodified used in in the PR bore. OE PR valve, boost valve, boost sleeve, boost spring, shim, and small spring. Line to lube drilled .093. No aftermarket boost valve spring was needed in either case. The setups call for fixed line pressure for the brake to function correctly. I had no idea that different pumps can result in a 30 psi swing, but that's what I'm seeing. I was skeptical about line to lube at first and was looking into the sonnax PR valve with built in check valve, but then heard that sonnax setup with it's nice drain back feature is sometimes not enough, and line to lube with stock PR valve was the goto. Fast forward and now certain vendors are now going with the adjustable boost valve setups and a modified PR valve (not the sonnax) in these 4L80E electronic shift transbrakes. I haven't seen these new modified PR valves in person, but I'm assuming they are similar to the PR valve that Superior has with the ground land to enable the pump to function very similar to how the line to lube works. Going to try this adjustable setup in the one that's 210 PSI and try and get it back down to 180 PSI and seal the line to lube hole. It's nice that these adjustable boost setups are available now on the market in the event that you get a pump that is putting out more pressure than expected, even with all OE unmodified parts in the pressure regulator pump bore with line to lube drilled. People complain about the price of these adjustable boost valve setups but fail to take into account how much R&D and testing goes into developing these parts. I'm just thankful they are even offered outside of full 4L80E builds so that a DIY guy like myself that builds the occasional unit for a local guy even has the option in the first place.

So to those of you that tested these EPC mods, adjustable pressure mods, and did all the ground work for the rest of us and openly and graciously shared this info, thank you once again!

 

i would assume chris just put 240 max as above that will generally shear the intermediate lugs off the case.

you can see my trans line pressure here. top left number on the lil holly screen.

I do my PR boost just like the CK/Trinity brake does. i see right around 200 unless the pump is in incredible (new, old-stock pump body) shape and then i'll see 220 or 230. pressure rise is generally faster as well. not many NOS pump bodies around anymore though.

 

Leave the pr valve as is with reverse land modified. Just use a stiffer spring to raise pressure. Max line pressure isn't as stable though as I've seen it drop through a pass (guessing the pressure pushes epc open).

 

Man, your idle pressure is really low. I face .002 off my inner gear and still have 70psi at 200*.

 

I assume you're facing .002 off the gear in an attempt to keep it from tearing the pump body up like some of the fixed pressure 80e seem to do?
If that is your reason for doing so, there's a better way to remedy that problem and you don't have to cut the pump gear and create a deliberate inefficiency in the pump