Okla. Stat. tit. 43 § 111.1(B) says,

B. 1. Except for good cause shown, when a noncustodial parent who is ordered to pay child support and who is awarded visitation rights fails to pay child support, the custodial parent shall not refuse to honor the visitation rights of the noncustodial parent.

2. When a custodial parent refuses to honor the visitation rights of the noncustodial parent, the noncustodial parent shall not fail to pay any ordered child support or alimony.

If that's not clear enough, in 1983 the Oklahoma Supreme Court ruled, 

The welfare of the child is paramount, and the duty of a non-custodial parent to support his or her child is contingent upon the needs of the children. It is not dependent upon the opportunity of the parents to exercise visitation privileges.

The duties of support and visitation are not interdependent and should be separately enforced.

Entitlement to child support is not contingent upon visitation rights. 

This was in the case of Hester v. Hester, 1983 OK 50, 663 P.2d 727.

So, we are told that "legally" custody and visitation are separate from child support.

However, as a practical matter, if a parent is behind on child support, that parent should expect extra scrutiny and skepticism from the judge if the parent who owes child support is in court for any reason. Many parents know that child support is separate from visitation, so they expect to be able to go to court to ask for changes to visitation or custody and have a level playing field. 

They won't. 

Okla. Stat. tit. 43 § 112(G) says,

G. In any case in which a child support order or custody order or both is entered, enforced or modified, the court may make a determination of the arrearages of child support.

This means even if neither side really brings up the issue of child support before trial, if the parent who was ordered to pay hasn't been paying, you can expect it to be brought up. The reality on the ground is that judges are very critical of parents who are not paying their court-ordered child support. By not paying child support, the nonpaying parent effectively hands the other parent a hammer: a powerful, blunt weapon that they can use to attack any claims for visitation or custody made by the nonpaying parent. Some examples:

The nonpaying parent says, "Judge, they're not taking the child to the doctor as needed. I am available and will take the child if given the opportunity."

The other parent: "It should would be easier to make appointments if we had the child support we need to make ends meet!"

The nonpaying parent says, "Judge, the child is making statements that indicate that the other parent is talking bad about me."

The other parent: "Judge, he's not paying child support. Life in our home is extra-difficult as a result."

Child support deliquency will be treated as a complete defense by the other parent, and the judge will likely be very critical of any issues raised by the parent who is behind on child support.

Times get tough and people get behind, but if you have custody and visitation issues, you cannot afford to get behind on child support. You cannot imagine the additional scrutiny you will go through. If you are behind on child support and go to court about an issue related to custody or visitation, you can expect to be asked about your hobbies and lifestyle in the most invasive, intrusive ways possible.

If you're behind on child support yet you frequent casinos, use tobacco, vape, travel, carry an expensive cell phone, play video games, eat at restaurants, drink at bars, donate to a church, hunt, fish, drive a nice car, or buy new tires for your car, your credibility will be absolutely destroyed in court. If you are behind on child support, you cannot afford any indulgence, any luxury, or any extravagant expense. Court will be a very unpleasant experience.

Child support and visitation are not equivalents. A noncustodial parent who pays all their child support and is being denied visitation cannot expect the custodial parent to receive the scrutiny and criticism that the noncustodial parent would receive if they did not pay child support. Being timely and current on child support is viewed as a minimum standard, and a parent who pays on time will not receive special credit or even acknowledgement for it.

All child-related matters are controlled by a concept called equity. Here is the rule you need to know about equity:

He who seeks equity must do equity and come into court with clean hands.

If you are ordered to pay child support and your child custody situation needs to be changed, you should prioritize making your child support current. Otherwise, you risk spending a great deal of time and money only to lose the case, and for your child to not get the help it needs, because you allowed the judge to be distracted by your nonpayment.