R34 De+t gearbox problems

[theonlypancakeofdoom]

Hey guys new here but at my witts end with my car and really looking for some help.

 

 

 

 

 

 

 

Time for a long story. Owned my r34 NA Auto for about 9 years now. Car was running well until about 4 years ago when I started to get the A/T limp mode whenever the car went to shift into 3rd gear. Wasn't to fussed at the time as the car was about to go into the shop for a full motor and gearbox build.

Car ended up with a full forged motor with turbo and all the bells and whistles which I haven't had a problem with. Gearbox was also completely rebuilt from front to back and absolutely everything is brand new. Car is running a haltech 2500 elite if that helps. 

Now to the pain. After all the money and things replaced it still has the same AT problem when it tries to shift to 3rd and it just sticks on 3rd gear limp mode from there on out. 

Car has always been and is still auto. It has the original box and motor in the car and me and my mechanic can not figure out why the hell it keeps happening. 

My next move is replacing the TCU module as it's separate in the GT model but other than that I'm lost

Any ideas or help would be much appreciated 

Picture just coz I like to show it off.

Thank you guys

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[GTSBoy]

Yuh, I'd start with swaptronics on the TCU also. It's probably a crappy capacitor or solder joint or something equally pissweak.

The good news is, if you have to throw it all away, it's relatively easy to run it all from a Haltech now.

[theonlypancakeofdoom]

@GTSBoy so are you saying that if I got rid of the tcu that the haltech could also control gearing? If so why in the world did my 

[theonlypancakeofdoom]

Tuner not do that in the first place?

[Kinkstaah]

This is a normal and expected outcome from doing what you have done.

I'm tired of going over what is going to be needed to fix it. The best solution is to not fix it, and to put a manual in.

Can't drive manual? Learn.

This is both the best solution and the simplest solution.

The more complicated solution is to reconnect the OEM ECU (yes, ecu) and reconnect its relevant parts to the TCU. Then you effectively splice the Haltech into the engine-parts of the OEM ECU, and run the haltech like an old school piggyback.

But it's a NA gearbox which will not last at all. It won't last if you put a shift kit in. It just won't last, period, so doing all of the above work will cost you thousands and leave you very sad.

Still don't want to go manual? You could go a Turbo gearbox and build that, but it's still a $10K adventure to get it close to being able to perform the way you want, including an aftermarket gearbox ECU, which gets wired in similar to the TCU's original setup. You will need aftermarket flex plates (they do not exist) and other bespoke things.

Your other option is to fully manualize the transmission.

The crux of the issue is that the R34 Turbo ECU has the gearbox/TCU pins on the engine ecu. The NA has them spaced out to a seperate TCU with the same inputs/outputs for Nissan reasons. It is plausible to rewirewire wires that lead to the NA TCM pins into their corresponding R34 GTT ENGINE ecu pins. This _will_ work, and then you could feasibly run a Nistune Engine ECU, which also only works for the Turbo/GTT ecu. The workshop manual pinouts are a treasure.

In theory you could look ingo the workshop manual and see what inputs the R34 TCM actually needs so it can operate the gearbox. It probably has wiring for power, tach, TPS and such from the engine ECU. Probably. I never looked into this.

Lots of ECU wiring and f**king about ahead for you. All of it more expensive than a manual swap. Much more complex than a manual swap. Much worse result than a manual swap. My car spent years at a workshop with them trying to figure this out until I did it with a mate in about 30 minutes by actually reading the manual.

Oh look I said manual again.
Go manual.

Any excuse you have about this is invalid. Refer to this post in the future, so you can re-read it and be like "lol shit yeah he was right I'm glad I went manual"

[theonlypancakeofdoom]

I understand the whole going manual thing but I had a work accident a couple years back where I lost alot of feeling in my left leg so I am unable to feel things like clutch pressure so unfortunately manual is not an option for me.

 

 

 

 

 

 

 

 

[admS15]

If that's the case and you read what Greg (kinkstah) wrote. You may as well go full retard and put a gearbox worth spending $ on, slap a zf8hp in it. 

[Kinkstaah]

24 minutes ago, theonlypancakeofdoom said:

I understand the whole going manual thing but I had a work accident a couple years back where I lost alot of feeling in my left leg so I am unable to feel things like clutch pressure so unfortunately manual is not an option for me.

 

Then you're in for a rough spot.

I would legitimately consider the crazy path of a BMW DCT conversion. Anything else is going to be underwhelming. Sensible me says buy a car with a decent auto in it. A V8 10 speed mustang is going to be a lot more fun and a lot more fast, and a lot more everything than the anguish of going down this path.

It really depends on how irrationally compulsive you are with regards to keeping a R34, or whether you want what an R34 can do. If in your mind this is a 100K, once in a lifetime car, BMW DCT is your answer. If logic is being applied in any way, shape, or form... A10 Mustang or one of the many other automatic-optioned vehicles is going to be far faster, simpler, easier, more enjoyable, less regrets.

[theonlypancakeofdoom]

8 minutes ago, Kinkstaah said:

Then you're in for a rough spot.

I would legitimately consider the crazy path of a BMW DCT conversion. Anything else is going to be underwhelming. Sensible me says buy a car with a decent auto in it. A V8 10 speed mustang is going to be a lot more fun and a lot more fast, and a lot more everything than the anguish of going down this path.

It really depends on how irrationally compulsive you are with regards to keeping a R34, or whether you want what an R34 can do. If in your mind this is a 100K, once in a lifetime car, BMW DCT is your answer. If logic is being applied in any way, shape, or form... A10 Mustang or one of the many other automatic-optioned vehicles is going to be far faster, simpler, easier, more enjoyable, less regrets.

I would sell it tomorrow if I could get what I wanted for it lol. But I'm so far invested that 

[theonlypancakeofdoom]

It would be silly to not get it done to sell it for more.

 

 

 

[robbo_rb180]

https://www.facebook.com/marketplace/item/707351387664345/?ref=search&referral_code=null&referral_story_type=post&tracking=browse_serp%3A5becc103-a884-4e65-93b8-d955e64cf3b4

[GTSBoy]

Ahhh. Greg's rage is palpable from here.

A version of Greg's ragey recommendation would be to look at https://support.haltech.com/portal/en/kb/articles/transmission-control and see that it should be possible to get this transmission (or, more sensibly, a turbo transmission, for the longevity reasons raged about) working direct from a Haltech ECU.

Having said that, in light of

22 hours ago, theonlypancakeofdoom said:

@GTSBoy so are you saying that if I got rid of the tcu that the haltech could also control gearing? If so why in the world did my Tuner not do that in the first place?

I can't speak for your tuner's willingness to get involved in trying to program the transmission control. He might not know that it's possible. He might be scared, or too lazy, or any of a number of other reasons.

Regardless, as per Greg's rage out - there is wiring to be done. You have to obtain all the wiring that is currently present at the TCU, work out which wire is which input and which output (and which might be able to be ignored, if they were originally signals to/from the ECU) and then marshal them to the Haltech.

But.....this now I think leads us to the answer. The TCU is probably having a shit fit because you have removed the factory ECU. It will not be happy about that, because they like to talk to each other. The TCU relies on some info from the ECU to do its thing, and not having that would be enough to make it go to limp mode. So, some of Greg's rant regarding putting the factory ECU back in, in parallel with the Haltech would be a (shitty) path forward.

Just wire it to the Haltech and get someone competent to set it up.

[theonlypancakeofdoom]

OK so update after today. Have plugged in a new tcu and actually have access to all gears and car shifts now. Still has AT light on but I assume that's now because this is a plain tcu and doesn't have any sort of tune on it

 

 

 

 

 

 

 

 

[Ben C34]

Good luck getting a tune on it...

[Kinkstaah]

1 hour ago, GTSBoy said:

Ahhh. Greg's rage is palpable from here.

Just wire it to the Haltech and get someone competent to set it up.

Not really rage, but "I turboed my NA auto and it doesnt work now" is a thing. Because people do this cheaply (not necessarily OP) it is generally "how much of my original NA car can I retain?"

Which is effectively nothing. It's _probably_ still cheaper to sell the NA and buy a turbo 😛

Still does not solve the issue of the cheese gearbox which won't survive 150kw, let alone whatever the forged motor is wanting to be. Haltech when I did it, did _not_ have an automatic gearbox controllable ECU for sale. Nobody did...

If the elite can do it, do it. The main issue will be finding an auto elec at $150/hr with the confidence to give this a try, but once you do it is fairly straightforward as long as the auto (any auto) has its inputs in the realm it likes. It just won't, and cannot, and never will be a straightforward plug and play solution.

Until someone makes an adapter I suppose, to go from the NA TCM to the GTT OEM ECU...