Reagan team still faces challenges on budget, trade, dollar. UNFINISHED BUSINESS

The Reagan economic agenda is not yet finished. In the 10 weeks before George Bush sits in the Oval Office, the Reagan administration plans to submit a budget for fiscal year 1990, make some important trade decisions, and calm the financial markets.

As a signal to those financial markets that his administration has not turned off the lights, President Reagan has decided that key staff members will work through the Thanksgiving holiday to finish the next budget. The Gramm-Rudman deficit-reduction legislation mandates the deficit drop from $136 billion to $100 billion.

On Wednesday, Mr. Reagan and Vice-President Bush began discussions on how involved the Bush transition team would be in that budget process.

One key issue, according to a senior administration official, is how to patch up the ailing savings-and-loan industry. According to most reports, the Federal Savings and Loan Insurance Corporation will need an additional $50 billion over the next five years to repair the damage to the industry.

``We will tee it up for the next administration,'' says the official, referring to the issue. ``There is a fiscal impact on the budget depending on how it is handled.''

The most pressing problem facing Reagan's administration is the foreign-exchange markets, where the dollar is bumping a 10-month low. The stock market also registered its concern about the twin budget and trade deficits, with the Dow Jones industrial average falling 78.77 points for the week. (Marketwatch, Page 23.)

Part of the concern of currency traders is the philosophy of Bush economic adviser Martin Feldstein, who believes the dollar must go much lower to resolve the trade deficit. In a speech last week, Mr. Feldstein repeated this view.

But yesterday, Craig Fuller, a leader of Bush's transition team, said the new administration will reject advice that it seek a lower value for the dollar.

Economist Alan Reynolds says the administration has to make it clear who speaks on dollar policy. ``Loose lips sink currencies,'' says Mr. Reynolds of Polyconomics, an economic consulting company in Morristown, N.J.

In three weeks, trade will become the focus when the US joins 95 other countries in Montreal for the mid-term review of the negotiations involving the General Agreement on Tariffs and Trade.

This week-long session will revolve around such key issues as agricultural subsidies and the elimination of roadblocks to trade in services. It ``will be an indication of how hard and tough continuing these negotiations is going to be,'' says Kelly Winkler, a spokeswoman for the United States trade representative.

And there are still ongoing trade disputes that must be resolved before Inauguration Day.

Prior to the election, US Trade Representative Clayton Yeutter rejected a request by the US Rice Millers' Association to retaliate against the Japanese, who refuse to import foreign-grown rice. Mr. Yeutter promised to reconsider the rice millers' plea, if the Japanese try to stymie efforts to limit agricultural subsidies.

The administration may also seek to retaliate against the European Community on Jan. 2, when the EC plans to bar US beef raised with chemical hormones. Yeutter will bring up this dispute again this week when he meets with EC officials in Brussels.

On the same trip, Yeutter also intends to complain to West German Economics Minister Martin Bangemann about the recent German decision to subsidize the foreign-exchange losses of Airbus Industries - the European aerospace consortium.

If the West Germans do not reconsider the subsidy policy, it is likely President Reagan will raise the issue when me meets with West German Chancellor Helmut Kohl in Washington on Wednesday.

The White House is also in the process of overseeing the writing of executive orders to implement the Omnibus Trade Act passed by Congress this fall.

The orders include appointing the newly established Competitiveness Council, setting up a mechanism to monitor foreign investment in the US, and establishing an office of barter to monitor countertrade - non-currency transactions between the US and other countries. The executive order will also bar government agencies from buying most goods produced by Toshiba Corporation for three years.

Meanwhile, White House officials are bracing for a flood of last-minute regulations proposed by outgoing Reagan conservatives intent on keeping their policies in place. ``The last few months of an administration are filled with requests by ideologues in agencies to promulgate regulations,'' says a senior White House official.