Originally Posted by
mudski
I reckon the tacho is out of whack. When I did the conversion from ZD to TD in my GU, I sent the loom to Killa Kustoms to get it cut and shut to suit the TD. It came back with a little box in the loom which is for the tacho signal. This box is adjustable too so they must calibrate it or something to suit.
I'm gonna guess you either dont have this box, or you do and it just not calibrated right. Theres no way you can do 100ks at 4000rpm in a TD. I had 4.3's in mine at it was at 2700rpm in 5th at 100ks. Now with 4.1's its at a nice 2450rpm. So you can't be at 4000rpm when you had 4.6's...
As PeeBee said too, the RD box is different and wont fit the TD. So we know the box is right. Can you take a pic of where the speedo sensor mounts into the box too? The GQ and GU boxes are different to each other, but i have seen GQ TD boxes used in GUs. But the speedo pickup is different.
If its a GU box, remove the sensor and tell me what colour the speedo gear is. Then take the car for a run with a GPS in hand that tells you the actual speed. We can then work out if you are actually going at the right speed too, if your speedo is out, you should be correcting this to by using a different tooth counted speedo gear.
Finding different speedo gears for a GQ box is near impossible these days.