me want to change joint strength in-game

//a simple question which i hope has a simple answer?

using UnityEngine;
using System.Collections;

public class tehscript : MonoBehaviour {

public Transform dude;
public float rotateSpeed;
public float dodgedat;

// Use this for initialization
void Start () {

	
}

// Update is called once per frame
void Update () {
	var conjoint = GetComponent().angularXDrive.maximumForce;
	
	if(Input.GetKey(KeyCode.G))
	{
	conjoint = 10;
	}
}// unfortunately its not changing the strength

}

You are assigning a temporary variable conjoint and adjusting its value and not assigning back to the joint component.

You want something like:

...
private ConfigurableJoint joint;

void Start() {
    joint = GetComponent<ConfigurableJoint>();
}

void Update() {
    ...

    if (Input.GetKey(KeyCode.G)) {
        joint.angularXDrive.maximumForce += 10;
    }
}