MLS I cant see how pinion angle can attribute to traction vs no traction in a cornering example. I can however see it attributing to power.
I beleive the noticed difference in traction is from suspension geometry not driveline angles.

Lemonhead I see where you are looking now. And I guess once the sump mods etc are done, its only a matter of adjusting the height of the engine and box mounts to vary the angles back and forth.
If the angles were getting bigger I guess you would look to the other way.

No, actually it is to do with the pinion angle.
You could go to the lengths of repositioning the arm mounts on the diff to bring the pinion angle back but you will find that the traction will be lost again.

Don't ask me exactly why it is so but thats what happens.

On a side note, sedans in speedway typically use 2 - 3 degrees nose down on pinion.

Another thing to bear in mind with changing the pinion angle is that when you increase positive acceleration traction you are decreasing negative acceleration traction by the same amount. i.e. the more traction you gain on acceleration the less engine braking traction you will have.

Monkeywrench, what you described is usually referred to as a torque arm and reduces the amount of spring wrap on high hp leaf sprung cars.

ok a little info I can add, as it seemed to launch pretty well out off the hole. Was a rx4 I had together once that on luke warm 245x17inx40ish slicks would get moving quite well. You could let the clutch out at 5500rpm and would just get out of there.
No idea what leafs are under it but they were different maybe lovells ? but as the set-up was quite stiff.(extra leafs) It had an added panhard rod bar and another bar that mounted from the top of the diff housing to inside the cabin and located to bracketry were the back seat should have been.
what looks to be the case before this modification. is that it was added as the diff flange/tailshaft yoke were wearing through the floor.this mod seemed cheap and effective but seemed to work well not sure you could talk you way out of it in a street car but

phunk, I agree with you, the difference in grip has come from the changed link arm lengths and the way load is supplied to the diff , the neg. pinion angle is unwanted but thats what works best on drag cars, speedway cars and rally cars.

It is another option to cut off link arm mounts and rotate the diff to a desired degree and weld them back on, in my eyes its a painful way of experimenting though, after the initial time it takes to make the adjustable arms it takes less than five minutes to adjust the angle.

I would be inclined to think the noticed difference in grip, is actually a result of the changed 4 link arm lengths and the way they make the vehicles body supply load to the wheels. And the changed pinion angle is just an unwanted result of adjusting the arms.
I believe you could correct the pinion angle by cutting the link arm mounts off the diff and rewelding them with the pinion set on the correct angle. And still have good grip with good pinion angle.

Matty, Sorry I should have mentioned before its in a Sunny (a few photos of it in my photo album)

I'm not the best person to discuss leaf spring set ups with on this site.

I do know though from what I have read that is on leaf spring set ups people usually set the pinion angle somewhere between 4-7 deg. neg. to allow for spring wind up.

Gary
Edit: I have just put a photo in my album of the T & B adjustable link arms.

so this 4 link set up is in what sort of car as im trying to picture in my head how your setup would look. also with vechiles that run a standard setup say a 1200 coupe with just a panhard rod added and no major changes( slick's fitted) you get massive spring wind and alot of nastie thing's start to happen at the rear of the car.

Hello monkeywrench and welcome to the site. Where are you from? Fill out your profile so we know abit about yourself.

Your question about changing the pinion angle is a good one, my answer is I have been adjusting the pinion angle (via the adjustable top and bottom four links I have made up) over the last couple of rallies I have been in. The changes I have made to this area have been by far the most significant changes I have made to the rally car with respect to getting power to the ground.

Prior to the changes the pinion angle was at 4 deg positve, I thought the car handled pretty good with that. After fitting the adjustable link arms and setting the pinion angle to 1 1/2 deg neg. I was completly amazed at the difference to the whole car it has made, it really is truly amazing.
No axle tramping off the line, the hook up is instant, before I would have to wait till after the apex of the corner before I booted it now I can literally attack corners before entering them knowing full well the arse end is going to stick to the road. This modification alone has given me nearly two seconds per Km and best of all it has given me more confidence in the cars handling.

So as far as I'm concerned if making the gearbox and the pinion angles is a lot of work but if it give me a chance of getting more power to the ground its very well worth the effort.

or what about changing the pinnion angle by re-positioning the diff by its mounts, platforms etc ? surely that would be work bit easier than cutting up the sump make new mounts to lower the engine?
anyways the only A series ive seen come loose was tightened and the bolts worked loose as they had no form of theard sealant on them if i were building a powie A series I would look into dowling the flywheel aswell