DatsunBanana

Had a go at the stuck crush tube this afternoon. Tried things like grips and a chain wrench first but wouldn't just twist straight off. So got to work with a drill. Started small and kept a depth stop on to make sure I didn't drill into the bolt. Made a line of drill holes all the way up and enlarged them. Then a combination of chisel and Dremel to split it all the way up. Levered the split to get oil in there and eventually it gave a bit while levering. Worked it back and forth with loads more oil till it was spinning freely, then with grips I could work it downwards and off. And no significant damage to the bolt (not by me anyway - just the 27 years of rust)

Drilled the rubber out on a slow speed and it didn't catch much at all. Probably only half a dozen holes was enough to shred the rubber and it dropped off easily leaving the inner sleeve behind. Will tackle that later

Thanks both. All good advice. Reminds me of drilling through stone wall for drainage pipe 😬 I'll let you know how I get on if I still have use of my hands afterwards 😅

So ... I got everything disconnected and started dropping the frame. Three of the four mounts started to come down but the fourth one (the one with the nut that gave me all the trouble) won't budge. The inner metal sleeve stays up tight against the chassis rail although the outer part of the mount drops a bit (and can be levered quite a lot more) but it's just stretching the rubber bushing. So I reckon there's some serious corrosion inside the inner sleeve and holding it tight to the lug at the top of the bolt. Tried everything I can think of so far: penetrating oil, whacking the top of the sleeve to vibrate it and wedge a screwdriver blade in there. I also tried to turn the inner sleeve a bit by hitting it with a chisel at the bottom. It's stuck solid. What do you think about cutting the rubber with a blade so I can drop the subframe around it anyway. Then worry about getting the inner sleeve off after? Will that work? Is it gonna give me even more problems?

I didn't know about induction heaters but checked them out and they look awesome but too pricey for the occasional job like this. And I'm too nervous to take a flame anywhere near there as the petrol tank is so close, although I was intrigued with the crayons suggestion 😁 I filled a coke bottle lid with penetrating fluid and raised it on the jack so the nut was submerged in it all night. Then went in with a tiny cold chisel and got it almost to the point of splitting but not quite (I didn't want to damage the bolt threads). Then I hammered a socket back on and gently worked it until I felt movement. And it's off 😀

Thanks everyone for the replies and suggestions. Got the seats out (hoping I could find some existing grommets but no such luck). By tapping and measuring etc. I could figure out where I could drill through if needed. But first I borrowed an inspection camera and managed to go through factory holes in the chassis rail and could see that the captive nut was holding steady which is why it could retighten. So it was indeed a stripped section of thread, so I applied downforce by levering the bolt head with a screwdriver and went slowly back and forth until it came out. Camera helped a lot cos I could monitor that the captive nut was holding tight. Now I just have one very seized main subframe nut to tackle 😅

Yeah, I'm pretty sure that's how it's going to end up. Mechanic suggested I cut a hole in the chassis/body to access the inside. I can cut the hole for access but will have to get someone else to help if any welding is needed afterwards. Things I'd like to know are: Assuming there's a captive nut inside, how's it fixed? And how can it be tightening but not fully loosening? If I cut a hole to access/replace a captive nut, is there a good place to cut for this one? Does it have to be at the side, or is there somewhere I can cut from above inside the car?

Trying to swap the rear subframe on my R34 and can't remove the L-shaped stay brackets between the front subframe mounts and the sill/chassis. I'm in the UK so rust is a problem. I've used loads of WD40 and then Tunap 103 for days beforehand. I backed off the bolts forward a bit, backward a bit repeatedly for ages to try and avoid snapping. They have all moved a few full turns. The one I've spent most time on has come loose and I can turn with fingers, and it will pull down and push up 2-3mm. But it won't come out. I can tighten it back up and loosen it off again repeatedly but it still won't come out. I assumed there's a captive nut inside but if that's broken loose then I can't understand why I can always tighten the bolt back up - I'd expect it to just spin both ways. Any ideas what's happening here? I can't visualise what's inside there to cause this.

Nice! That makes perfect sense now - thanks 👍

Couldn't quite see what you mean from your photos, can you share a pic of the drilled hole and spacer? Still promising myself that one day I'll fit all the manual bits I've got in the garage. Is the rusty one the R33 pedal?

You may have already seen it but there's been a bit more discussion on this and the other valves (swirl valves) in the NA RB20 and 25 NEO differences thread in the Naturally Aspirated Performance forum. When I posted above I was still trying to decide what to do. I've been running 5 years now with the hose just disconnected from the diaphragm and all runs really well. You've got me thinking again about trying to connect a boost/vacuum line from the plenum now to see if there's any noticeable difference.

That 'pump' is a vacuum tank, I guess just a reservoir for holding the vacuum. On the 20DE looks like it's used for both the swirl and torque butterflies. One line is to the plenum and the other two will go to your torque valve solenoid and swirl solenoid. The solenoids will have their own lines to the actuators. The solenoids seem to switch the actuator hose to either the vacuum tank or the air filter side of the throttle body. This is from page EC-3 in the manual. On 25DE the tank is just for the torque valve so I binned that and the solenoid and related hoses and used the old tank take-off for my boost gauge I think. From experience I know the torque valve is under spring pressure keeping it in the default open position. I don't know about the swirl valves but if they are sprung to open position then removing the vacuum tank, solenoid and hoses from the actuator would (I'm guessing here) let them spring quite firmly open (??) Page EC-44 in the manual gives info on the RPM threshold for the solenoid ON/OFF signal.

The main torque valve shouldn't need hacking as it defaults to open without the vacuum pipe connected (at least on the 25DE). Not sure about the swirl valves but in your pic they look open by default. On the 25DE I used a GTT ECU but it doesn't have the signal to control the valve. Other discussions seem to suggest at boost the valves won't do much but would still be cool to know what it's like controlled by an aftermarket ECU.

Have you tried Conceptua tuning on eBay? They have a few options for 33 gtst. Great to deal with too.

I was always of the same opinion as Kinkstaah that using a GTT auto ECU would be complicated. If you've got the R34 service manual, pages EC11/12 show that GT auto and manual have the same ECU wiring that uses a separate transmission control unit and the GTT auto has the transmission control built in to it. Page AT3 states that plainly. As per the diagrams, wiring for manual GTT ECU is same as GT auto/manual so that's what I used on my auto NA+t. It works fine and just uses the original GT transmission control unit to look after the auto box. As mentioned above, popular opinion is that there could be problems if the transmission circuit inside the GTT auto ECU creates conflict or doesn't talk with the GT transmission control unit still in the car. Pages EC13/14 will show you which pins are different and what they control. On page EC11, pin 79 of a GTT auto ECU (multiplex communication) is shown as only being for TCS/ABS but on page EC12 for non-turbo it also goes to the separate GT TCU. Pages AT8/9 have the transmission circuit diagrams (top right corner on page AT9 shows the connections from separate TCU to ECU). If you're gonna give it a go, those refs might help and if you get it working report back to feed the knowledge base. R34Nur posted a couple of weeks ago and said it worked fine with auto GTT ECU but that does go against popular opinion.