Still trying to eliminate the vibration that I have since installing a new quaife reverse box and props.

Convinced it was the angle on the short front prop, I removed the rear prop and spun the front prop and reverse box in the garage up to 85mph but had no vibrations.

Would it make a difference not being under load? I'm definitely not going to try with both props connected!

Should not make any difference as they don't balance them under load

If the prop is fine which it should be by the sounds of it, then I can only think that other parts of the drivetrain must be the culprit. Of course, the reverse 'box could be out of balance somehow, though if there is no vibration while in the garage, I would start by looking at the diff which can be affected by load (I'd have thought), then work outwards to the wheels.

Could it be possible that something completely unrelated could be at fault? Wheel weights (front and rear), tyre pressures, tyre bulge etc? It's not particularly helpful but anything that moves or gets faster as vehicle speed increases could be to blame.

Take the wheels off and try running it up (on axle-stands) and see if it still wibbles.
If it does, note the speed it does it, fit a couple of worm-drive clips to the prop and try it again. If it gets worse, move the heavy bits of the clips 180degrees and try again. Keep moving them until it gets better. If it's still not right, add another two clips and repeat.

I'll try running it tomorrow on stands with the wheels off.

Everything was fine before I fitted the box and new props so hadn't really thought anything else could be causing it.

I will check the tyres for bulges though.

Thanks for your help

are there any sliding joints that have been apart? Are there any U/Js out of phase?

Make sure you remove your wheels before running it up, I smashed my gearbox tail-stock with a bad prop running it up on axle stands, I don't think I had my wheels fitted, but be careful.

My money's on the reverse box, I had the same issues, and ended up changing to an electric reverse.

I had a similar issue with my Quaife box and had to send it back to Quaife to have the bearing replaced. It had only done about 1000miles at the time. In that case you could actually feel the play (up/dpwn) on the output shaft.

Pete

The box has play on the output shaft. Spoke to quaife and they were really helpful the chap said send it in they'll sort it out.
Bit annoyed because it's brand new from demon tweaks, just spoke to there customer service and didn't get much help at all.
I've spent a lot of money with them in the past and they won't be getting anymore.

Also make sure that one side doesn't start going the other way, trust me it can and that will knock the diff out.....