Hewland Gearbox Fgc Service Manual Illustrated Parts List

Working With the Hewland FGC: What You Actually Need

The Hewland FGC (Formula Grand Championship) gearbox is one of those units that shows up in vintage Formula cars, Sportscars, and a lot of hillclimb machines. When you're opening one up and need to figure out what's what, the illustrated parts list is the only thing keeping you from guessing. I've rebuilt three of these over the years and the manual does exactly what it says—it just doesn't make it obvious at first. The manual isn't published by Hewland anymore in any official capacity. The company was acquired, assets changed hands, and the documentation has scattered across a few different sources over the decades. The most reliable copies I've come across are held by the Hewland archive which is managed through the old engineering records community, and a few aftermarket publishers like Thoroughbred Toys and Motorsport Manuals who've reproduced selected sections. Your best bet is checking the classic racing car forums where members scan and upload the full documents. Search for "Hewland FGC service manual" on the HPD or Speedtalk boards and you'll usually find a direct PDF link posted by someone who owns the original. I should note that many of the scanned copies floating around are low resolution. The illustrations are small and the part numbers can blur together if the scan wasn't done well. Make sure you're getting a high-quality copy or you'll be squinting at a diagram for hours.

How the Illustrated Parts List Actually Works

The FGC is a close-ratio five-speed sequential gearbox. The illustrated parts list is organized by sub-assembly, not alphabetically. You'll find sections covering the main casing, input shaft assembly, output shaft pack, dog engagement set, selector mechanism, and the oil system. Each illustration shows the components in an exploded view with callout numbers that correspond to a table listing the part number, description, material where relevant, and sometimes a quantity per assembly. The key detail most people miss is that Hewland frequently updated part numbers during production without maintaining a separate revision index in the manual itself. If you're looking at a gearbox with a serial number in the 4000s and the manual you're reading was printed for early 3000s units, some of the drawings will be off. I ran into this head-on when I was sourcing a replacement synchronizer for a mid-production FGC. The part number in the manual didn't match what was stamped on the actual component. The workaround was cross-referencing with a later manual revision that covered the updated synchronizer design and confirming the fitment by measuring the dog teeth width rather than relying purely on the number.

Reading the Diagrams Correctly

The exploded views use a consistent convention but it's easy to overlook. Components that appear on both the input and output shaft packs are often listed with two different reference numbers in the same table. This is because they may look identical but have different tolerances or heat treatment. The synchronizer rings for example are numbered separately depending on which gate they serve. If you order based on a visual match alone without checking the reference number against the table, you'll get the wrong ring and it won't engage properly. Another thing that catches people out is the oil seals. Hewland used a mix of standard metric seals and their own proprietary dimensions on older units. The parts list will show a part number for a seal but if you go to a regular industrial supplier they might not carry that exact specification. I found that several of the seal sizes in my manual corresponded to what Metrix or Elring would catalog under completely different numbers. Having the internal diameter, outer diameter, and thickness measured and written down before you shop makes this way faster than trying to match numbers across multiple catalogs.

What the Manual Won't Tell You

The illustrated parts list is a reference tool, not a rebuild guide. It will show you that a certain bushing exists between the selector fork and the shift drum, but it won't tell you the acceptable wear limit. You need to measure clearance with feeler gauges and compare against the service limits that Hewland published separately in their technical bulletins. These bulletins are harder to find than the main manual and are usually only available through the same archive channels or specialist Hewland rebuild shops. The FGC is also known for having slight variations between race-spec and road-spec builds. The illustrated parts list doesn't always distinguish between these clearly. A gearbox from a Formula Ford setup might have a different final drive ratio cassette than one from a Sportscar application, and the casing drawings can look nearly identical even though the gear sets are different. Always verify your gear ratios against the original car's specifications before assuming the parts list matches your setup exactly.

A Few Practical Notes

If you're doing a full rebuild, the parts list will help you identify everything that needs replacement but don't assume you can order directly from the numbers without checking availability. Many of the older parts are no longer manufactured by Hewland and are either surplus stock or being reproduced by third parties. The shift dogs for instance are occasionally available from specialists like TransTec or even machined from billet if you can provide the correct specifications. Budget extra time for sourcing rather than expecting every item to be readily available. The selector mechanism is the part most people get wrong when rebuilding. The illustrated parts list shows the detent balls, springs, and rails clearly enough, but reassembly order matters. If you put the detent springs in backwards or miss a rail clip during reassembly, the gearbox will throw gears under load. I've seen this happen more than once on track. Take photographs as you disassemble and follow the manual in reverse rather than trying to remember the sequence. Oil capacity for the FGC is roughly 1.6 liters using a 80W90 gear oil. The fill and vent plugs are on opposite ends of the casing and overfilling by even a small amount can cause leaks past the output seal. The manual covers this briefly but the practical issue is that the sight glass or dipstick method isn't always accurate depending on how the gearbox is mounted. The safest approach is to fill to the bottom of the fill plug hole with the gearbox level and run it briefly to distribute the oil before topping up if necessary.