Registrations of three wheelers, mainly used as taxis, were down 15.8 percent from a year to 5,724 units in May. JB Securities said finance companies were tightening credit as non performing loans (NPLs) and repossessions picked up.
Mini truck were down 20 percent to 999 units, light trucks were down 20 percent 295 units and medium trucks were down 13 percent to 153 units.
Large trucks were down 41 percent to 70 units.
"The accentuated NPLs faced by finance companies in heavy truck leases is dampening demand since there are a number of repossessed vehicles coming into the market," JB Securities said in a research note.
"Some leasing firms are choosing to reschedule/restructure lease rentals since the loss on liquidation is very high."
But there was a pick-up in private car and motor cycle registrations, a trend seen for several months.
Private car registrations were up 1.8 percent to 1,965, SUV sales were up 21 percent to 404 and motor bike registrations were up 8.7 percent to 15,661.
Private car sales were dominated by hybrids where rulers have reduced taxes. Brand new cars including luxury vehicles and SUV are driven by tax slashed permits given to state workers.
In May 580 units of brand new cars were registered, down from 668 units a year earlier but in line with a month earlier. Micro branded cars, which are locally assembled with parts imported at a lower tax picked up to 172 units from 103 units in April.
Used or re-conditioned car registrations rose to 1,369 units in May 2014 from 1,262 units a year earlier.
Of that 1,115 units were hybrids.JB Securities said financing share was about 50 percent stimulating credit growth. If high taxes on small imported cars are lowered to more reasonable levels, more economic activity and credit will be stimulated, the brokerage said in a note.
Small cars were hardest hit following tax hikes that started in 2012 in at attempt to fix a balance of payments crisis.
In Sri Lanka there is a belief among rulers and bureaucrats that imports - particularly car imports - are a cause of balance of payments trouble, which is really caused by central bank credit or printed money.
JB Securities said in the premium brands segment 14 Mercedes S-class vehicles have been registered, which could have been cars imported for a commonwealth summit meeting last year.