The stock fell 4.03 per cent to settle at Rs 91.60 on BSE.
At NSE, shares of the firm sank 3.83 per cent to end the day at Rs 91.60.
On the volume front 45.12 lakh shares changed hands on BSE and over 2 crore shares were traded on NSE.
The company had sold 11,054 units in July last year.
Sales of heavy and medium commercial vehicles declined by 7.39 per cent to 8,182 units last month as against 8,835 units in the year-ago period, the company said in a statement.