Thirty-one years ago, the production of the Syclone, Typhoon, and Sonoma GT was launched from GMC Truck Division bringing the world the fastest production...

Thirty-one years ago, the production of the Syclone, Typhoon, and Sonoma GT was launched from GMC Truck Division bringing the world the fastest production trucks ever to be made at the time. Famed for their faster than a Ferrari track times and neck snapping 0-60 acceleration, as quickly as it started, it was equally gone just as fast.

While some trucks went lovingly into collector status mode and carefully stored away, others were enjoyed on the weekends with the occasional spirited drive and car show, and of course lots were busy chalking up hard mileage down the track and looking for that unknowing victim at the next stop light on the streets.

The market today is full of trucks with varying histories and condition. While the low mile gems still can be sought out, most of the trucks today all show a bit of age with some mileage and modifications. Potential buyers need to be aware that these trucks require a caliber of maintenance that is unique to the SyTySoGT. Built as a high performance truck, there are many parts that are shared with the s-series platform it was built on, but the trucks also used specific parts that can only be found on the Syclone, Typhoon or Sonoma GT.

This buyer’s guide is designed to cover both the common areas of the Sonoma/Jimmy platform but also focus on the unique features of the Syclone, Typhoon, and Sonoma GT and what should be considered when looking to purchase one of these sportmachines.


Research these trucks and ask yourself if this vehicle is worth your time and money. The SyTys (excluding the SoGT) are trucks that require a high level of maintenance in order to run at peak performance in both stock and modified form. If you are not mechanically inclined, be ready to learn or be sure you have someone who is certified or can be trusted to work on your truck. Just like you wouldn’t take a Ferrari to a Honda Dealership or a shade tree garage, most mechanics are not going to be knowledgeable or able to diagnose specific issues that the SyTys are known to have.

“Many can afford to buy a Syclone or Typhoon, but many can’t afford to own a Syclone or Typhoon.”

If you can bring along a current owner or someone who has knowledge of these trucks when going to look at a potential truck to purchase, it is to your advantage. What an inexperienced eye might miss, one who has been around these trucks will quickly be able to point out both the positive and negatives.  You don’t know anyone? Ask. You’d be surprised how many people will offer to help or might already know the truck and be able to give you history on it. The SyTy community has been around since the mid 90s and many of our resources are spread out across many social media platforms.

Some helpful resources to ask questions or seek help:

Read the ISTR SyTySoGT FAQ page for commonly asked questions!

  • Check for broken or cracked cladding pieces. The more common pieces to break are the fender arches due to the tabs that secure them to the fender break plus they tend to see the most interaction of touch when you’re bent over your fender working on the truck. While OEM pieces can still sometimes be sourced through private sellers, certain ones are becoming harder to find and can go for hundreds of dollars. Today’s market has opened up to fiberglass alternatives.

  • Syclone cladding should appear as a matte black finish. The discussion has been brought up that the cladding was indeed painted with the matte finish using a flex agent from the factory due to owners being able to peel what seems like a layer of paint off their aged cladding. If the cladding appears to be various shades of color (sun bleached), this is an indication of a truck that did not receive routine treatment with cleaners/plastic shine products and usually in a very dried out brittle condition.  ALL Typhoon cladding for 92 and 93 trucks are painted! Refer to the FAQ for correct color breakdown on Typhoons/SonomaGTs.

  • Sonoma GT cladding shares the same front and rear bumper as the SyTys while the rest of the pieces are unique only to the Sonoma GT. The front fender bumperettes are a common broken piece along with the rear bed corners. The SGTs have skirt cladding that flows underneath the cab and on the lower front quarter of the bed.

  • Look for cladding that is not properly riveted onto the truck. It is common for the front bumper to be misaligned to the front of the fender arches. This could be either from incorrect placement on the bumper hangers (can be easily adjusted by 2 bolts), broken cladding tabs, or a possible sign of a past accident. Be sure to inspect this closely and ask questions. The front fender arches are known to be weak on the tabs around the fender and can easily break off resulting in a lost piece of cladding on the road. Giving a gentle pull on each piece of cladding can help indicate loose or broken pieces. We emphasize gentle. Lets not rip cladding off of a truck you may or may not purchase.


Do a typical inspection as you would for any vehicle for rust. This is more of a concern on trucks that are in areas that snow or near the coast due to salt exposure. It is not untypical to see light rust scale on the frames or suspension. Use your discretion for how much is too much. Other specific areas to look for rust:

  • Check the bottom of the doors
  • Check the bottom of the tailgate (opening the tailgate will expose the bottom side much easier)
  • Rust is known to hide behind cladding. Make sure to reach up behind any panel possible.
  • Typhoon – Check around the gasket seal of the rear windows
  • Typhoon – Check around the rear glass
  • Check body mounts

While many trucks still wear their original paint, after 25 years, many have also been repainted. Check for signs of paint work along any rubber trim or overspray on the wheel wells. If the truck has been repainted, ask if the cladding was removed when painted. A quality paint job should have had the cladding removed to paint the entire body. Cladding can also hide hidden secrets (see rust above).


Check the FAQ for color breakdown.

  • Check if it’s a correct 92 color scheme. Other than Blk/Blk, Radar Blue, and Raspberry, all 92s should have painted gray cladding.
  • Silver Typhoon decals (specific for 92)
  • Two-tone grille:  Body color + gray headlight buckets and center portion. If grille is all one color, suspect replacement or paint work.
  • Has door escutcheons (plastic piece surrounding door handles)

Check the FAQ for color breakdown.

  • Check if it’s a correct 93 color scheme.
  • Gold Typhoon decals (specific for 93)
  • Monotone grille: The grill is the same as the body color. NO gray headlight buckets or center portion.
  • NO door eschucheons (plastic piece surrounding door handles)

Know the interior differences between the 92 and 93 Typhoon by reading the SyTy FAQ page.

Syclone & 92 Ty Seats – Check for the lumbar support bulb on the front part of the seat. This is a common thing to break on the trucks as the hose becomes hard and brittle and breaks off at the pump bulb. 93 Ty seats are electric controlled! Test to ensure the seat electronics are properly working, including positioning.

The emergency jack should be located behind the passenger seat for Syclones and with the spare tire on Typhoons.

Check the center console lid. This is also a common area of wear and tear due to usage. The outer cover is known to peel up or the spring to the button will break and not allow the lid to latch and lock (can be opened without depressing the button).

Check gauge needles. The oil pressure needle has been known to flip all the way over and become stuck on the lower needle stopper. The fix for this is to take part the gauge cluster and flip it back around by hand.  Some have added a 2nd stopper to not allow the needle to flip.

Check for cracks in the dashboard. Common places are around the vents and speaker grilles. 1st generation dashboards are becoming increasingly hard to source and expensive to purchase when in good to mint condition.

Check the passenger side carpet under the dash area for any sort of moisture or signs of wetness. Smell the carpet. A common problem with the trucks are the heater cores leaking. When this happens, coolant will dump onto the passenger floorboard. If you notice a coolant smell and the carpet is wet to the touch, changes are the heater core is leaking. The heater core can easily be fixed using this article.

The Typhoons are famous for having what is called “window squeak” which is due to the back window latch having worn out and rubbing on the release hook while driving. This is very common among all the platforms (Jimmy/Blazer/Typhoon) and is easily fixed with an aftermarket latch system from Sportmachines.


Many trucks today have been lowered by means of using rear drop blocks and then turning the torsion keys on the torsion bars to lower the front. Inspect that the rear blocks are property installed. If the rear wheel seems to be off center of the wheel well, changes are setback plates where not used. Re-centering the rear wheel can be fixed easily with the installation of setback plates.  Many also go the route of lowered leaf springs for the rear.

Check all bushings and greased parts for signs of cracks or tears. This includes areas such as – upper/lower control arm bushings, tie rod ends, ball joints, idler arm, u-joints, and even CV axles.

Inspect the forward propshaft. Stock trucks used a booted propshaft that commonly get ripped or torn, therefore destroying the joints (think in the same manner as a CV shaft). There are stories of propshafts failing and denting/destroying the floorboard right under your feet. The stock propshaft is not serviceable.  Inspect the boot for any signs of rips and leakage. Many trucks have switched to an upgraded double cardon joint propshaft. These proshafts tend to be serviceable as well as much stronger than the stock propshaft. They range from $300-500.

The Typhoons came standard with a ride leveling system in the rear. There is a pump located on the driver side behind the rear wheel. This pump is hooked up to air shocks.  If enough weight is put on the rear of the truck to engage the system, you will hear the pump run and the rear of the truck will slowly rise back up to proper height. If the pump is in working order, you can usually make it engage by sitting on the tailgate. Many pumps no longer work or have been disengaged due to lowering the truck. Is it necessary to have? If you plan to haul heavy items in the truck on a regular basis, yes, consider it. If not, there is no harm in not having it and many have choose to unplug it all together. This is something to consider if you are looking at a lowered truck as well. If your shocks have a leak, you will notice the pump running on a regular occasion to keep up with the leak and level the truck. Inspect the shocks and air lines for leaks.


Many trucks on the market today have some degree of modification under the hood. This can vary from minor reliability upgrades to heavily built and bolted on parts. Due to the range and degree of modifications, this list is an overview of more of the commonly known areas to focus when looking under the hood. This list mainly covers stock to mildly modded trucks with upgraded stock components or standard bolt on parts.


Blow-by occurs when the explosion that occurs in your engine’s combustion chamber causes fuel, air and moisture to be forced past the rings into the crankcase. This causes a loss in power and oil dilution. In short, a motor with blow-by means a definite rebuild coming soon.

Start the engine and unscrew the cap from the oil-filler neck. Look for smoke or vapors coming out of the oil filler. If there is a lot of smoke, the rings/valve guides are worn and the smoke you see is blow-by. If there is no smoke, hold your hand above the filler neck. If there is a lot of air coming out, it’s a sign of blow-by.


Run your hand along the radiator hose, specifically nearest the area of where the alternator is. You are feeling for any cuts in the hose (always on outer ride side of the hose, facing the engine bay) caused by the alternator fan. This is a quick indicator of bad engine mounts due to when the engine torques over, the bad mount allows the alternator fan to touch the radiator hose and cut into it.  Motor mounts aren’t fun to do on the SyTy, so a quick “bandaid” fix is to install a torque strap which is typically bolted on around the alternator and down to the frame. Various style straps have been made using chains and hooks or billet brackets and turnbuckles. A worn or broken motor mount isn’t a deal breaker when buying a truck as solid mounts are readily available, but the work to install them is a bit demanding due to limited work space.


If the truck you are drooling over to purchase has a stock intake tube, ask the owner if they could please take it off the truck to inspect. Yes, this sounds inconvenient, but you possibly could uncover a ticking time bomb or worse, a hidden issue that would have gone unnoticed. Check each end of the tube for cracks or if it missing altogether.  The intake tubes are prone to cracking when the hose clamp on either end is overtightened. This has resulted in way more than one incident of a piece of the intake cracking, breaking off, and feeding the turbo….thus destroying the turbo.  Which leads into….


If you have the intake tube removed, take an opportunity to inspect the turbo and shaft. You may notice a small amount of oil sitting on the turbo inlet, this is normal. If there is an excessive pool of oil, this could be an issue with the turbo itself or the PCV system.  Reach into the turbo inlet and grab onto the intake wheel (the truck should not be running of course) and check the in/out and side/side play. The shaft should have little to no movement. If you can feel the shaft moving excessively around, the turbo is ready for a rebuild. Inspect the intake wheel for any damaged or bent blades – protip: use the camera on your smart phone!


Here is an incomplete list of common modifications and upgrades you may find under the hood:

  • Adjustable Fuel Pressure Regulator (AFPR)
  • Intercooler lines changed from stock metal to 3/4″ hose (various methods to route)
  • ABS Delete
  • Stock intercooler replaced with “Air to Air” (A2A) intercooler system
  • Intake elbow or aftermarket cold air box (replaces factory stock intake tube – see above)
  • Electric fans (single or dual setups)
  • Injectors (stock injectors have “red tops”)
  • Battery relocated – Common places to relocate are bed, under the bed, back of truck (Typhoons) or lowered in the fender area
  • Oil filter relocated to the block