During the end of the 1970´s and the beginning of the 1980´s the fourth series of Rc-locomotives was produced and delivered. General improvments were done. The Rc4-locomotives weigh slightly more: 78,0 tonnes. The max speed was the same as the Rc1-2-locos, 135 kph. The Rc4-s were used in all sorts of trains from the beginning but are now only pulling freight trains. Some of the Rc4-s still have the original orange paint scheme. Between 1976 and 1977 Amtrak, USA, borrowed the loco Rc4 1166 as X 995 for test driving. They drove it with a maximum speed of near 200 kph (125 mph). The test-drive lead to orders of similar locos from Amtrak, and other train companies in USA, to Asea. 130 Rc4-s were produced.

There is also a Norwegian version of the Swedish Rc4-s, El16, which also has, apart from all equipment from Rc4, higher power output (4440 kW vs. 3600 kW), an extra electrical braking system and reinforced and pointed front (and rear) so the loco can run through snow obstacle without damage. Some of the El16-locos were not needed in Norway so in the beginning of 2003 the Swedsih train company Tågkompaniet (TKAB) bought six El16-locos for use in Sweden. TKAB are painting the locomotives in their red and white paint scheme. The El16-s weigh also a little bit more than the Rc4-s, 80 tonnes.

One additional version of the Rc4-locos was buildt. A variant for the Ore line (Malmbanan) in the very north of Sweden. Their designation is Rm. The differences here are higher weight, 90 tonnes; lower gear ratio so the max speed is only 100 kph (63 mph) and stronger bogies and suspension. Today the Rm-locos are used in freight traffic all over the country. When the Rm-s only were used on the Ore line they had automatic couplings, but now they have conventional screw couplings. The Rm-s don´t have disc brakes, they have electrical dynamic brakes and shoe brakes.

Rc4 1263 hade en tillverkningsskylt som det stod Strømmen Verksted vid första turen till Göteborg.

Rc4 korgarna 1263-1282 är dock inte tillverkade av Strømmen utan är tillverkade av Nohab i Trollhättan.

Utrangerte RC4 lokomotiv:

Rc4-1292 (Ulykke ved Lerum 1987-11-16)
Rc4-1300 (Ulykke ved Lerum 1987-11-16)