Robert Bowen
Robert Bowen Editor
1/4/18 1:15 p.m.

Manual transmissions are crude, simple devices. Most of the internal parts are big, heavy and made from steel alloy, which makes them tough. The basic technology—helical gears and sleeve synchronizers—has been around for more than 100 years. This is good, because we enthusiasts tend to ignore our gearboxes until something goes wrong—like when nasty noises appear or the shifting becomes hard.

Some transmissions are better than others, of course, but very few stock manual gearboxes are truly flawed. Most are plenty strong for weekend track and autocross use. Full-time racing is even possible with an unmodified box in a light, low-powered car.

While hard use is unlikely to result in catastrophic failures, it does put more stress and wear on the all-important gearbox than street driving does. This doesn’t mean you’re doomed to suffer shifting problems and transmission failure, however, as there are a few simple things you can do to keep your transmission swapping cogs like new. In fact, here are six tips that should reward you with a trouble-free transmission.

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jdoc90
jdoc90 New Reader
1/5/18 7:51 p.m.

Of course none of this will help an alfa romeo 5 speed transmission 2nd gear downshifts .The grunch was added to the dna and cannot be overcome even by stem cell transplant .lol  So the 4% of Americans who can use a manual transmission can now keep the 1% of cars still running with one going longer until they are outlawed and replaced by a toaster with wheels ! viva la manuale !

mad_machine
mad_machine MegaDork
1/5/18 9:45 p.m.

Both of my manual equipped cars come with fragile transmissions. Both are flawed from the factory simply because they were designed for lower power levels than the engines they are bolted to. The Fiat Box is not a bad one, but it's biggest flaw is that it uses springs to hold it in gear instead of springs to push it out like most modern boxes.

The saab 900 box was never designed to hold the 185hp the turbo engine puts out. Combine that with the heat of the turbo next to it and the temeratures of the engine oil that uses the side of the box as the sump, and you are looking at a transmission doomed to an early death.

Empathy will go a long way. When I was much younger I destroyed a rebuilt fiat box in the course of a summer by doing reverse to forward burnouts. Reversing the power through the gears quickly shredded that transmission. Older and hopefully wiser now, and with many years driving big commercial trucks with manuals, I have no urge to powershift or rush a shift.

Vigo
Vigo UltimaDork
1/5/18 11:03 p.m.

I disagree with the statement that rev matching without double clutching will do anything to ease the job of the synchros. IF the clutch is working properly, there will be almost no power transferred while the clutch pedal is pressed, so the speed difference between the mating gears will not be substantially reduced. If you have an unsynchronized reverse gear, it's pretty easy to tell whether your clutch imparts any rpm to the input shaft and all of its meshed gears by simply slowly shifting into reverse while the clutch pedal is pressed. Most (maybe all?) unsynchronized reverse transmissions use an idler gear that slides back and forth to engage. If the gears being meshed by the sliding idler gear are not at a stop, the 'clash/grinding' of the gears can be heard or at least felt through the shifter. If your reverse idler doesnt 'clash' trying to engage reverse while revving the engine with the clutch pressed, that means that all those gears are stopped and that by extension revving the engine while the clutch pedal is pressed is not going to do anything for your synchros because it doesnt transfer enough torque to overcome the friction of all the parts and actually impart rpm to the input shaft.

What rev-matching without double-clutching will do for a racer is reduce the shockload to the drive tires when you release the clutch. If you downshift the trans without rev-matching, you are asking the tires' contact patch to transfer energy from the movement of the car to spin up every component upstream of the synchro you just engaged by probably thousands of rpm. The input shaft, all of the gearsets, the clutch disc, pressure plate, flywheel, crankshaft, rods, pistons, timing parts, cams, everything on the belt drive, yadda yadda yadda. Spin that 100+ lbs of crap up by a couple thousand rpm in a fraction of a second. That's a pretty huge load, sometimes enough to break the tires' traction even while coasting in a straight line. If you happen to be already using 90% of your available traction turning around a racetrack, that additional load on the tire will cause you to break traction and depending on which wheels are driven you'll either oversteer or understeer.    

 

 Cliffnotes: rev-matched 'single-clutched' downshifts are less likely to cause you to lose control while turning hard on a racetrack. Rev-matched 'double-clutched' downshifts do that AND reduce wear on your synchros both on the track and on the street.

 

mad_machine
mad_machine MegaDork
1/6/18 7:50 a.m.

In reply to Vigo :

rev matching also reduces the "reverse" load on the clutch, transmission, and differential as those units now have to deal with torque coming FROM the drive wheels back to the engine rather than the other way around. If you can bring the revs up to where they would be, it is a softer transition to the entire drivetrain

Knurled.
Knurled. MegaDork
1/6/18 9:29 a.m.

In reply to mad_machine :

Depends on if your transmission has weak synchros or weak mechanicals.

 

Of course the real fix is to not use the clutch at all, no synchros = no problem!

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