Our CR-X budget build-up kicks into gear (literally), with a transmission rebuild courtesy of The Gearbox Factory and the delivery of a new clutch from Xtreme.

BOX OF TRICKS

The Racer-X project is all about doing things on the cheap. We’re achieving this by doing much of the work ourselves and, where possible, re-using good parts that already came with the car, like the Toda lightweight chromoly flywheel we had BNT grind flat for us in last issue’s update.

With all builds, though, some things are best left to the professionals. Case in point: the project of the CR-X’s 5-speed gearbox. On any performance rebuild, unless you know the car’s intimate history from the day it rolled off the production line, to a large extent you’ll be going in blind. Our Honda is 18 years old and lived most of its life in Japan, so we definitely are. We’re lucky, then, that the CR-X’s original B16A engine is still in good health and we have no need to pull the head off the block. But the gearbox, with its strange whining noises and graunchy gear selection, is another story. It’s just another one of those things you never wish for but which you really should expect.

Although gearboxes are really quite simple in the way they operate (see How It Works, page 36), the inner workings are a puzzle of shafts, gears, bearings, hubs, synchros and forks. They are, therefore, not the sorts of things someone with limited mechanical knowledge should attempt to pull apart and try to rebuild, let alone repair.

That’s exactly the reason why we left the Y1 trans in the very experienced hands of The Gearbox Factory.

Very well versed in the highly specialised art of gearbox repairs, rebuilds and reconditioning (it comes with being in the business since 1976 33 years!), The Gearbox Factory guys had a good idea what they’d find inside the box before they even cracked it open. Those suspicions were confirmed when its guts were laid out on the bench.

First up, the manual transmission workshop manager, Chris, showed us what the gearbox was going to be up for: a whole lot of machining, gear lapping and the replacement of some bearings, including the worn main diff bearing, which was definitely the source of the gearbox’s whine. It might sound bad but Chris said all these issues were to be expected in a gearbox of this type and age, and therefore it was a pretty straightforward job. Time to get into it.

With five-and-a-half years’ experience at The Gearbox Factory, transmission technician Paul was the man for the job. He also pilots a DC2 Integra, so we knew we were in good company!

The first thing on the list was to remedy the mains gear’s worn 'dog’ teeth issues. These small teeth are straight cut and allow a hub to lock a gear into position. To obtain a clean mesh between the two parts, each tooth needs to guide an opposing tooth into position without clashing. Normally these teeth start life quite pointed and sharp, but over time and use they wear down and flatten off, and therefore don’t help the gear shifting cause, but instead cause graunching. Instead of replacing those gears completely, it was Paul’s first job to re-shape each tooth with a grinding stone. It’s a slow and tedious task, but one that needed to be done especially on the lower gears, which tend to take the biggest hammering.

Once all the machining was done it was assembly time. The pinion shaft was placed in the vice (with aluminium jaws so as not to damage it) and the first and second gears were installed, followed by the cluster gears for third to fifth. Once all gears were in position and the clearances between them checked very important for lubrication the outer pinion bearing was fitted. Because it’s such a tight fit, the bearing was first heated to expand it, and then dropped on. The main nut followed and the pinion shaft was complete.

It was a similar story for the main shaft, with first and second cluster gears going on to align with the first and second main gears on the pinion shaft, followed by the main gears for third, fourth and fifth, and finally another bearing.

With the shafts complete, Paul turned his attention to the differential, which, if you can remember back to last month’s progress report, was found to be one of the limited slip variety, and better still an aftermarket job (OS Giken, we’ve since discovered).

Since our last visit, Paul had pulled the LSD apart to check its condition, and as Chris had suspected, it was in fine form and duly put back together. All Paul needed to do was fit new bearings on both sides and it was ready to be dropped into the gearbox casing. Because those bearings had been heated as well, it required some subtle jimmying, but quickly slotted nicely into position.

Once the diff was in and the opposite main shaft bearing fitted into the case, Paul connected the selector forks to the two shafts, picked them all up together and fitted them into their rightful positions.

The selector toggle fitting followed, and the two cases were ready to be siliconed and bolted back together. A job well done!

The Gearbox Factory lads were super-quick at their work, and we’re now looking forward to feeling the improvements once the CR-X is driving again. Cost-wise, for a similar type of gearbox rebuild (excluding the diff strip-down and rebuild) you’re looking at a minimum of $500 plus GST worth of labour, with the cost of any new parts additional. For us that was really only a few bearings, so the rebuild wasn’t an overly expensive task by any stretch of the imagination. Cheers to Keith, Chris and Paul for all their work!

How it works

The primary job of a gearbox is to take the power output created by the engine and transform it into drive to turn a vehicle’s wheels. The clutch acts as a bridge between the two components, and allows the engine (which is always turning as it runs) to connect with the gearbox (which, until it gets some drive, isn’t turning) by controlling the slip between them. When you push the clutch pedal the engine and gearbox are connected to each other; when you take your foot off the pedal they engage.

Inside any regular modern front-wheel-drive manual gearbox you’ll find two shafts and a differential. The main shaft (or input shaft) transmits power from the clutch to the gearbox, and the pinion shaft (or output shaft) transmits the power straight into the differential and out through the axles.

On the two shafts are collections of gears that are in constant mesh. In the case of our Honda gearbox, the pinion shaft features both first and second gears and cluster gears for third, fourth and fifth. The main shaft, on the other hand, features the cluster gears for first and second and the main gears for third, fourth and fifth. The main gears are not splined to their respective shafts, but because they are meshed to the cluster gears (which are splined to the shafts), they are always turning. When you select a gear, the shifter mechanism moves the shifter rods, which in turn move selector forks into position, and lock the chosen gear solid (from its freewheeling position). To ensure the gear change is smooth, each main gear has a synchromesh to slow the gear down and synchronise it for a clean engagement. Once the gear is connected, drive is transferred to the differential, with the selected gear’s ratio determining how quickly the vehicle’s wheels will turn based on revolutions from the engine. The higher the gear, the lower the ratio and the faster the achievable speed.

Slipping Clutch

When we pulled the CR-X’s engine out and cracked the gearbox off in Racer-X’s first installment, we found an Exedy clutch with a three-puck plate that was well passed its use-by date. There was sweet bugger all friction material left on the pucks, explaining exactly why it had been slipping so much in third, fourth and fifth gears. Whichever way we looked at it, the clutch was destined for the bin, meaning we had to fit something new. For that task we put a call through to BNT NZ, the local distributor for Xtreme Clutch.

Although relatively new to the performance clutch world, Xtreme has quickly made a name for itself, supplying its wares to the motorsport community and sponsoring a few big-name players along the way, including local drifters Gaz Whiter, Fanga Dan and Daynom Templeman. From what we had heard, Xtreme’s products are well built and reliable. Even better, they’re reasonably priced right up Racer-X’s alley.

Josh Strang is the product manager at BNT who looks after Xtreme Clutch for the local market, and he was happy to talk us through our options for a clutch. These ranged from an Xtreme HD setup, which included a heavy-duty pressure plate and organic clutch disc a basic HD clutch upgrade right the way through to an Xtreme Multiplate carbon twin-plate job for serious high-horsepower track-work only. Our ideal was something in the middle: a decent race-style unit that was not going to be too much hassle to use on the street. Accordingly, Josh recommended an Xtreme DSBHD setup, which basically comprised a heavy-duty pressure plate and a sprung-centre six-puck ceramic button disc that would provide aggressive but positive operation and not wear anywhere near as quickly as the three-puck style clutch it was replacing (see side panel: Hot Clutch Tip). The kit would also come with a new release bearing, giving us everything we needed to get the job done. Sounded good to us. We placed the order and a couple of weeks later it turned up, ready for installation.

We must point out that Xtreme also had a few performance flywheel options, but because we already found a decent Toda job in the car that was still useable, and since we’re on a tight budget, we passed them up. If you’re doing a performance clutch upgrade and you’re running a standard flywheel, a performance clutch/flywheel package is definitely the way to go.

Hot Clutch Tip

If you’re in the market for a performance clutch setup, it’s imperative that you get the right gear for the job. If track performance is the priority but street use is part of the equation, a multi-puck sprung arrangement is a good choice. As far as these types of clutches go, the more pucks the more contact between the clutch disc and pressure plate, and that ultimately equals better driveability and a clutch that will last longer. Choose wisely or you could end up with a clutch that’s a bitch to drive in traffic and is dead before you know it.

Words: Brad Lord Photos: NZPC

This article is from Performance Car issue 152. Click here to check it out.