I rec a tax free disability pension due to an injury from the nyc sanitation dept.
I was just approved for ssd benefits to start in about 2-3 months and some back pay... due to the disabiltiy pension do I have to pay taxes ?

It depends on how big of a lump sum you will receive, but, yes, you probably WILL owe some taxes.

I guess it depends; as long as you have ONLY the SSD benefits as your income, then it isn't taxable. If you have other taxable income, then it may become taxable.As you are approved for SSD benefits, your benefits may be taxable. You may find yourself with tax obligations if you have other sources of income besides your disability payment, or if your spouse earns a substantial income.If you file a federal tax return as an "individual" and your provisional income, MAGI , I mean is between $25K and $34K, you may have to pay income tax on 50 percent of yourSSD benefits. If your MAGI is above $34K, up to 85 percent of your SSD benefits is subject to income tax. If you are married and file a joint return, you may have to pay taxes on 50 percent of your benefits if you and your spouse have a combined income that is between $32K and $44K. If yourMAGI income is more than $44K, up to 85 percent of your SSD benefits is subject to income tax.

If the retroactive check covers any months of 2012, that portion can be subtracted from your 2013 taxes.