Torque arm and 5th coil questions

[TWISTER]

Been looking over my car and noticed that there seems to be significant spacing between the drive shaft and torque arm towards the front of the car. Approx 4-5 inches. Is this common? What effects would it have on the car if i moved it closer to the driveshaft(moving it to the left)? Will that enhance forward drive at all? Or am i just wasting my time and need to leave it alone.
Also i have seen several post about 5th coil springs and locations. My question is this. When moving the 5th coil shock and spring towards the back of the car do you typically stiffen the spring when doing so and softening spring when moving it farther out? Also what about just softening or stiffening the spring but keeping it in the same location to help initial acceleration traction? I read on a couple of threads where some of you talk about how important the 5th coil set up is to forward drive and initial throttle traction. We are having some difficulty gettting the initial traction that we need and feel we should be getting. I do know that there are other areas of the car you can work on to effect this area as well, i am just curious as to the effect of the 5th coil on my area of concern.
Our track starts out with a lil bit of bite and we are usually a bit tight for hot laps, or right on the verge of it anyway, but for feature time the track changes dramatically and after about 5 laps into the race we are so free and have little to no forward drive and exit speed while other cars are just rocketing off the same corners with what appears to be much more drive than we have.
Any help on this would be greatly appreciated.
Thank you.

[Matt49]

Lots of things to consider here.
When thinking of a torque arm, I like to put my elbow on the work bench with my forearm flat on the work bench. Your elbow is the center section of the rear end which is what is generating the torque under acceleration. Take a 10 pound chunk of lead and put it in your hand and lift it about two inches while keeping your elbow on the workbench. Notice that you probably felt your elbow get a little heavier or push into the workbench. This is like the rear downforce effect of the torque arm. It’s natural to then think that a heavier spring would always be better but this will cause too much force on the contact patch and you could shear the contact patch and just buzz the tires.
Back to spring rate in a minute but let’s talk spring position real quick. Take that same 10 pound chunk of lead and put it about half way between your wrist and elbow. You’ll find it much easier to lift there than when it was in your hand because it is closer to the source of torque (your elbow). So given the same amount of torque you actually lifted it FASTER. But a lead weight is different from a spring. A spring gets “heavier” as it is compressed and eventually builds up potential and starts pushing back on the torque arm. You’ll often hear people use this simple maxim: 5th coil closer to the rear end provides more instant traction and forward bite off the corner but diminishes down the straight and 5th coil further from the rear provided less instant traction and forward bite off the corner and more down the straight. I think simple model above helps illustrate WHY this holds true. With the 5th coil further back, the spring can be compressed much faster given X amount of torque and hence will begin to unload sooner. Once the spring is unloading the lift bar is not providing as much downforce to the rear wheels which means forward bite will drop off.
The typical rule of thumb on spring rate is that a heavier spring is better for a heavier race track. Remember from our experiment that we could fell a heavier weight in our hand provided more force between our elbow and the workbench. Likewise, a heavier spring on the torque arm will provide more downforce to the rear end. But as I said, if it’s too much, you can buzz the tires very easy because of shearing the contact patch. But if traction is near limitless (e.g. hooked up clay surface) more spring works better. If the track is slick, you need the softer spring to absorb that force and keep the rear tires firmly planted but not so much that it shears the contact patches.
A couple of other nuances that many people don’t consider:
1) Moving the 5th coil changes the lift point that the torque is pushing into the car. If it gets too far forward, you could have a tendency to unload the front tires and pick up a corner exit push.
2) As the torque arm rises, the front of the rear end is rotating upward which is changing the relative location of that end of the j-bar (where it is mounted to the pinion plate). Too much axle wrap can take j-bar rake out of the car and free the car up.
The 5th coil is still important to forward traction but not nearly as important as it was when these cars had both rear springs ahead of the birdcage. Back then, we didn’t have nearly as much anti-squat and birdcage indexing which generates a ton of forward bite in the LR spring behind configuration. The 5th coil was about the only way to generate forward bite and plant the rear end. It’s still very important but not like it used to be given the other tools available to generate forward traction.

You'll want some gap between your lift bar and drive shaft. If you get it too close, you could end up getting the 5th coil into the driveshaft if the car ever sits down hard on the LR. 4-5" is not extreme. We usually try to keep the 5th and 6th coil as straight up and down as possible when viewed from ahead or behind.