- Thu Jan 17, 2008 1:38 am
#37919
TROUBLESHOOTING MANUAL TRANSMISSION PROBLEMS
Note: When Referring to a “Nicked” or “Beveled” gear teeth below, it will look like the following.
- Overview.
Honda manual transmissions have constant mesh gears for all forward speeds.
The locking mechanism for any individual gear consists of a synchro sleeve on the shaft which is able to slide sideways so that teeth on its inner surface bridge two circular rings with teeth on their outer circumference: one attached to the gear, one to the shaft (one synchro sleeve typically serves for two gears; sliding in one direction selects one transmission speed, in the other direction selects the other. Fifth gear has it’s own single-sided synchro sleeve). When the rings are bridged by the synchro sleeve, that particular gear is rotationally locked to the shaft and determines the output speed of the transmission. Transmission troubles are usually caused by the wear of these associated parts.
- When shifting gears, there is a “grinding noise”.
Why: This is normally caused by a worn synchro ring, or are shifting to fast. The grinding you hear are your gears hitting each other when they engage. Synchros are designed to match speeds between the synchro sleeve and your gear sets. If you shift faster than your syncho ring can match the gear speeds, they will grind. If the synchro ring is not replaced, the gears themselves will begin wearing.
You have several choices:
1). Slow down your shifting.
2). Double clutch between gears.
3). Replace the synchro for that gear set.
How to Fix:
You will want to replace your synchro ring for that gear set. If it grinds all the time, even with slow shifting, then it’s a synchro ring problem.
- While in gear while under power the shift lever pushes back against you.
Why: This is because the inner teeth on the synchro sleeve and that particular gear have worn to the point where their contact edges are no longer square, but beveled. The gears are pushing against themselves and are trying to disengage.
How to Fix:
Replace Gear set and synchro sleeve that has the worn teeth. The synchro rings should also be replaced as they are worn and no longer acting as a “clutch” between the gears by this point.
- Transmission sometimes pops out of gear, especially at slow speeds, or going up a hill.
Why: This is because the teeth in the gear sets are worn and "Beveled" to the point that they actually disengage the transmission.
How to Fix:
Replace Gear set, synchro sleeve and the synchro ring for that gear.
- When driving there is a “Roaring” or “Growling” noise from the transmission.
Why: There is a bearing going out in your transmission. Most commonly it’s a main input shaft bearing. It could also be one of the needle bearing sets on your Main or Counter shaft.
How to Test: With your transmission open and gear clusters out. Put your finger on your main input shaft bearing (pressed into the bell housing side) try spinning the input shaft and feel for resistance or roughness, also try rocking it back and forth. If it is not smooth or has a lot of resistance, it should be replaced.
To test the needle bearings, rotate the different gear sets on each shaft, if you feel or hear roughness, take apart your gear clusters (description here, under “REPLACE SYNCHRO/CHANGE GEARS”) roll your finger inside each “needle bearing cage” and feel for smoothness or resistance. If it is not smooth or there is resistance, the bearing should be replaced.
How to Fix: Replace bearing that is bad. Replacing a “main input shaft bearing” is discussed here.
To replace one of the “needle bearing cages” you simply install the new one in place of the old one. Use a diagram of the main and counter shafts before you take them apart, they are available here.
Note: When Referring to a “Nicked” or “Beveled” gear teeth below, it will look like the following.
- Overview.
Honda manual transmissions have constant mesh gears for all forward speeds.
The locking mechanism for any individual gear consists of a synchro sleeve on the shaft which is able to slide sideways so that teeth on its inner surface bridge two circular rings with teeth on their outer circumference: one attached to the gear, one to the shaft (one synchro sleeve typically serves for two gears; sliding in one direction selects one transmission speed, in the other direction selects the other. Fifth gear has it’s own single-sided synchro sleeve). When the rings are bridged by the synchro sleeve, that particular gear is rotationally locked to the shaft and determines the output speed of the transmission. Transmission troubles are usually caused by the wear of these associated parts.
- When shifting gears, there is a “grinding noise”.
Why: This is normally caused by a worn synchro ring, or are shifting to fast. The grinding you hear are your gears hitting each other when they engage. Synchros are designed to match speeds between the synchro sleeve and your gear sets. If you shift faster than your syncho ring can match the gear speeds, they will grind. If the synchro ring is not replaced, the gears themselves will begin wearing.
You have several choices:
1). Slow down your shifting.
2). Double clutch between gears.
3). Replace the synchro for that gear set.
How to Fix:
You will want to replace your synchro ring for that gear set. If it grinds all the time, even with slow shifting, then it’s a synchro ring problem.
- While in gear while under power the shift lever pushes back against you.
Why: This is because the inner teeth on the synchro sleeve and that particular gear have worn to the point where their contact edges are no longer square, but beveled. The gears are pushing against themselves and are trying to disengage.
How to Fix:
Replace Gear set and synchro sleeve that has the worn teeth. The synchro rings should also be replaced as they are worn and no longer acting as a “clutch” between the gears by this point.
- Transmission sometimes pops out of gear, especially at slow speeds, or going up a hill.
Why: This is because the teeth in the gear sets are worn and "Beveled" to the point that they actually disengage the transmission.
How to Fix:
Replace Gear set, synchro sleeve and the synchro ring for that gear.
- When driving there is a “Roaring” or “Growling” noise from the transmission.
Why: There is a bearing going out in your transmission. Most commonly it’s a main input shaft bearing. It could also be one of the needle bearing sets on your Main or Counter shaft.
How to Test: With your transmission open and gear clusters out. Put your finger on your main input shaft bearing (pressed into the bell housing side) try spinning the input shaft and feel for resistance or roughness, also try rocking it back and forth. If it is not smooth or has a lot of resistance, it should be replaced.
To test the needle bearings, rotate the different gear sets on each shaft, if you feel or hear roughness, take apart your gear clusters (description here, under “REPLACE SYNCHRO/CHANGE GEARS”) roll your finger inside each “needle bearing cage” and feel for smoothness or resistance. If it is not smooth or there is resistance, the bearing should be replaced.
How to Fix: Replace bearing that is bad. Replacing a “main input shaft bearing” is discussed here.
To replace one of the “needle bearing cages” you simply install the new one in place of the old one. Use a diagram of the main and counter shafts before you take them apart, they are available here.
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