How to level dual extruder?

More pics of back, top and side might help...

Also, those two nuts on the bottom may have something to do with it.

How is this mounted to your printer?  If the base sits flat on your printer carriage, then perhaps a cheating method would be to put a shim under one of the mounting flanges.  This assumes that they are off by only a very small amount.

From the one pic, my guess is that the nuts on the threaded portion are there for locking in place. If you back off that nut, you may be able to thread the nozzle in/out as necessary.

It's just a theory, though.

It's really a theory, because it's really hard to tell the height difference with only eyes.

Thank you IronMan, your method is so detailed! I will try it later. And thank you TheBaron.

I tried to use vernier calipers to calibrate thier height difference today, and it works! It performs better than before.

I have a Replicator 2X and both extruders have to be the same height or one of them will knock the print over.

using the lowest extruder level the bed using a piece of post a note.
then lower the other extruder until  the post a note feels the same under both nozzles.

I do the leveling with the bed up to temperature .
after I think I have it t I do a dual test print.
sometimes it takes me 3 to 4 times before I have it rite .

What if the bed is not level itself?

So what's the precision of feeler gauge? Can it reach 0.01mm?

Since getting my Geeetech Prusa i3 PRO C dual extruder 3D printer about a month ago no matter how many times I pulled the extruder apart and tried to get both extruder's the same hight, I couldn't.

Not saying I'm not happy with the printer or Geeetech. As both have been great. The printer wasn't too hard to put together and think they have fixed most of the issues they have found to sell a printer that is pretty much build and print. Deliver was amazing with the item taking around 5 days to arrive from China To Melbourne, Australia. Plus the email support for pre sales has been quick and concise. The Wiki and forums has also been a great source of information to complete the addition of the Auto bed levelling, but thats a different topic.
Once built with minimal adjusting I managed to print a small object straight away no problem. So thats a big win in my book.

Now back to my winging.

As the extruder are not the same hight when you go to print an object that was big enough for the second extruder to travel over the printed part from first extruder it would either damage the print or pull the printed part off the bed.

After taking the extruder off and on like 15 times over the month to get it working I had screwed the second extruder up high and used it as a single extruder printer. Till today. I found the energy to give it another go.
After messing around for a few hours, I came to the conclusion that its just a design flaw and the threads where slightly different. So no matter how much i played with it, as is it wouldn't work.
As to get the extruder's even close to level one extruder needed to turn half a turn around and then both the extruder's Y Axis was different.
This wasn't so much of an issue as you can fix that with an offset but you still cant get them to be millimetre (sorry America we have real measurements here) perfect.

With such small differences making an impact i thought there had to be a better way and thought if there could be a way to mod the design. Figured as I cant use the second extruder if i damaged it in the mean time wouldn't be a big deal to wait till a new one arrived.

What I came up with was to drill out the thread (i know but stay with me ) in the hole where one of the extruder's screwed in. This way it could slide up and down to get it exactly the same as the other.
I then drilled a hole in the side and threaded it with a M5 Tap set. As I didn't have a Tap and Die set I was lucky to find a 3 piece Tap set with M5,M6 and M8 for around $10 aus. As the my extruder mechanism is Aluminium, which is very soft. I suggest you do much smaller hole then normal then Tap that.
Once this new hole was drilled and had a thread I then put in a M5 Grub Screw.
The reason I went with a M5 was that if I made a mistake or the thread didn't work I could then go up a size in the Taps I bought. Though seeing as though this was my first experience with threading something I did a few tests on a scrap bit of metal first.

You can see the black grub screw in the pictures, I have circled them in red. The location I did the hole for the grub screw I put in green. Sorry for the bad pictures I didn't think about posting my idea till after it was all back together and working.

So the process to get them the same was to set the un-modified extruder to the correct high that would reach the bed before the mounting hardware. Then slide up and down the other extruder till that was correct.
Basically using the same method posted in this video (https://youtu.be/XGpcueIfUn8) but with the modded extruder being able to be adjusted to perfection.
The nut that you normally have to use to set the extruder high, is still needed to be tightened as this holds the 2 parts of the extruder mount together. But the top part is held in my the grub screw, so just need the bottom one.
I also noticed that that when i tightened the nut it would change the high ever so slightly so found the amount it would change by and added this to the hight so when you tightened it, everything was at correct hight.

Please let me know if you needed something explained better if I haven't made sense. Hope this helps your issue like it has mine.