1990 4.3SS Chevy Syclone Prototype

During the stages of the GMC Syclone’s development into production, many prototype trucks were built from already existing trucks which were converted to test mules for various areas of testing. Once such truck is the 1990 4.3SS Chevy Syclone Prototype.

Actually VIN’d as a 1990 S-15, the 4.3SS was one of the trucks used in engine and drivetrain testing. The 4.3SS could be considered your standard sleeper truck as its unassuming appearance both on the exterior and interior wouldn’t give way to the truck’s potential and power. That is, until you notice a logo on the fender in gold vinyl lettering that states – “4.3SS Turbo”, a hint that GM and PAS were up to something.

Cladded in forrest green paint, the exterior is what you would find on most production S15/Sonoma/S10 trucks. The rubber wheel arch flairs, tonneau cover, steel front and rear bumper, and a 1-piece grille is most likely how the truck was originally built before it was chosen as a test mule. No cladding is on the truck. The only visible outside change to the truck is it wears production Syclone/Typhoon rims wrapped in Firestone Firehawk SVXs (what the production SyTys came with). Instead of the standard GMC emblem center cap, Corvette crossed-flags center caps where used. We can assume this was before the GMC center caps where ready for production.

The interior of the 4.3SS remains untouched with no signs of post-production alterations. A light gray cloth bench seat, manual roll-up windows, and the standard analog gauge cluster with a column shift setup is about as interesting as it gets. There is non leather wrapped “X-pattern” steering wheel and no logo emblem resides on the glove box door. The truck does have the standard cassette player with optional equalizer radio.

Underneath the hood is where the action starts. The 4.3SS truck is complete with a 4.3 turbo V6, its visual appearance the same as a production Syclone only with one missing element; a blank upper intake with no “Syclone 4.3 Turbo” machined into it. The intercooler reservoir does have the cosmetic cover plate on it – a piece not found on the production Syclone but is on the Typhoon. The exhaust system is the same as production with a dual muffler setup and pipe exits. Also like the production trucks, it also has a 700R4 4-speed automatic with an AWD setup.

Today, the truck is privately owned and makes regular appearances at the SyTys@Carlisle event during the Annual Carlisle All Truck Nationals located in Carlisle, Pennsylvania. It is one of the few remaining verified prototype trucks that still exist and in driving condition.