Good idea, might try that myself, I usually run a loose diff and a medium tighness slipper.

You should be able to spin the gearbox freely by hand when constructed without the pinion attached. If it is tight then it could be a number if things. Badly meshed gears, missing spacer on the layshaft, or the diff is way to tight.

Take it apart and check that everything is seated properly. Take apart the diff and clean it rebuild it. Put some black grease on the thrust race. Compress the diff spring with a pair if pliers a couple if times and take your time to put it back together. Tighten it a bit at a time and checking it by inserting a Allen wrench in each outdrive. Holding them together and trying to turn the pulley. Once it has become very difficult to move the pulley by hand give it a quarter turn more just to be on the safe side. Your diff should feel very smooth and when you turn one outdrive the ithe should turn in the opposite direction.

When you come to putting the gearbox back together make sure you have all the parts in the right place. When you put the long bolts in to hold the gearbox case together and also hold the motorplate in place only do them finger tight, this can stop it binding and also helps to nit strip the threads in the motorplate.

Thanks for the advice, I'll give it a go later.

I checked the hubs and found one was tighter than the other, sorted that out and now with wheels in the air both spin at the same rate, which is one thing sorted.

at the moment it moves, but doesn't take off, visibly not using all it's available power, so something slipping somewhere - will try your method for re-building the diff and checking the gear box.

how much grease (if any) should be in the diff?
and if so, where should, and shouldn't it be?

This is a good little guide for rebuilding your diff

http://mrmagoo-rc.blogspot.com/2011/...-diff.html?m=1

This is pretty much the way I do mine.

Diff build and working, think it might be slipping slightly from time to time,

just got to get the clutch set up now, although running it a little loose while motor and gear box wear in might be a good idea?

Do you still have the original diff washers and balls fitted?, also are you using the original bronze bushes in the centre of the diff & outdrive or replaced with bearings?

I found that if I fitted 2xbearings in the centre of the diff they were very slightly to wide,meaning the diff wouldn't tighten fully, now use 1x bearing and 1x bush in the centre of the diff,works fine, I am also using the kevlar diff,1xmetal idler and 1x nylon idler and AE spur. I'm not sure on the diff balls, I never fitted the kit ones, put some others in that I had in a parts box.I also started to use AE diff plates, direct fit, I have had no probs with these, but others have so take care! if you use them

Been running for around 3xmeeting with a 6.5 and all is well so far:thumbsup:.

I've built it following kit instructions with the kit parts, no upgrades and no intentional modifications :)

Ahh, may be worth changing the diff balls,and upgrading they are not the best and could well have flat spotted by now,thus causing the diff to slip and also sound rough as old boots. I have read that most people have done this