WASHINGTON — In pitching the $1.5 trillion tax overhaul, Steven Mnuchin, the Treasury secretary, has said repeatedly that the plan will pay for itself through a surge of economic growth and that over 100 people in Treasury are “working around the clock on running scenarios for us.”

Mr. Mnuchin has promised that Treasury will release its analysis in full. Yet, as the full Senate prepares to vote on a sweeping tax rewrite, the administration has yet to produce the type of economic analysis that it is citing as a reason to pass the tax cut.

Those inside Treasury’s Office of Tax Policy, which Mr. Mnuchin has credited with running the models, say they have been largely shut out of the process and are not working on the type of detailed analysis that he has mentioned. An economist at the Office of Tax Analysis, who spoke on the condition of anonymity so as not to jeopardize his job, said Treasury had not released a “dynamic” analysis showing that the tax plan would be paid for with economic growth because one did not exist.

Instead of conducting full analyses of tax proposals, staff members have been running numbers on individual provisions or policy ideas, like lowering the tax rate on so-called pass-through businesses and figuring out how many family farms would benefit from the repeal of the estate tax. Activity has picked up more recently as Treasury has sought to provide technical assistance to the Joint Committee on Taxation and the Congressional Budget Office for their estimates.