Kara's manual transmission woes

manual-transmissions
nissan

#1

After listening to this week’s show, I am truly curious. Does resting your hand/arm on the gearshift lever have any effect on the lifespan of the synchros, or is this another booooo-gus answer from the Tappet Brothers? I have two cars of the same make and love driving the 5-speed, while the awful three-speed slushbox barely qualifies for daily driver duty. With the small dimensions of the car, I generally rest my hand on the parking brake handle and not the shift lever, but this worries me. Are Click and Clack right or am I being paranoid?


#2

Click and Clack are right. You should keep your right hand off of the shiftstick until it is time to shift. But the emergency brake handle is a safe place to rest your hand, so long as your hand doesn’t feel a need to engage the e-brake while driving.


#3

The answer is: maybe.

Some shifters, espeacially aftermarket versions, have an adjustable mechanical stop to keep the shifter from pushing the synchronizer too far. The same stop is what you would be pushing against if you rest your hand on the shifter. Other shifters have no such stop, so you’d be wearing the synchronizers.

Resting your hand on the shifter is a poor idea in either case, since you probably don’t know whether you’ve got a stop or not.


#4

Yes, transmission damage can occur because of this habit. The worst vehicles I’ve seen for this problem have been Subarus and I can’t even remember how many Subaru transmissions I’ve repaired due to this very habit.

The weight of your hand is multiplied by the gear shift lever. This can edge the shift rail in the transmission off of the detent a little. In turn, this forces the shift fork (which is attached to the shift rail) to rub against the edge of the synchronizer sleeve. Eventually the constant metal on metal contract wears the shift fork fingers along with the sleeve and this causes too much free side-play in the fork/sleeve assembly.
When this occurs the transmission will start jumping out of gear due to the inability of the synchronizer inserts/hub/sleeve to remain stationary and the only fix is a rebuild.

What gear it jumps out of depends on the type of driving and how often the hand is at rest on the gear shift lever. Generally speaking, someone who has this habit on a vehicle that sees a lot of stop and go city driving will have a trans that jumps out of 3rd or 4th gear as those are the predominant gears being used.
Someone who spends a lot of time on the open road in 5th gear for example and who has this habit may have a trans that jumps out of 5th. C and C are right on this one.

(And this is a habit that one should not have on automatic trans cars either as it’s possible that fluid pressure could be affected and in turn this could cause subtle slippage problems. This is bad news on an automatic.)