Manual Transmission Problems
Manual transmission issues can develop because of high mileage, abuse, or lack of proper maintenance, however, they’re rather rare. Most manual transmission problems originate not with the transmission itself, but from connected parts like the clutch assembly, linkage, or driveline: the parts that transmit turning power from the transmission to the wheels. Also, as we discuss below, symptoms that appear to be coming from the transmission can return from unrelated components of the car.
Diagnosing the Issue
The key to diagnosing your manual transmission problem is to collect elaborate data concerning the actual problem. for instance, does the problem appear in only one of the gears, solely at a precise speed, only when turning, only when downshifting, or after having serviced the clutch or another transmission component? Are you able to feel a vibration? Are you able to hear a clunking or grinding noise?
Symptoms of a Bad Transmission
Here are some symptoms which will indicate a worn-out transmission, all of which we discuss below:
- Odd sounds (whirring, squealing, bumping, or thumping)
- Grinding noise
- Transmission jumps out of gear (into neutral)
- Difficulty shifting gears
- Car stuck in one gear
- Car that can’t get into gear
- Leaking transmission oil
This guide can get you started on distinguishing the source of those issues. You will need to investigate more and keep in mind that manual transmission configurations can change from one model to the next.
Remember that this guide only deals with symptoms coming from the manual transmission (or transaxle) itself. Some symptoms that may appear to originate within the transmission really come from the clutch (or another system), and vice versa.
- Odd noises that may come from the transmission
The most common cause of a loud transmission is low oil, causing the gears or internal assembly to hum or whir. If a loud transmission does have enough oil, the lubricant could also be contaminated with metal shavings or particles. Insufficient or contaminated oil might cause the transmission to become noisy in some or all of the gears, however, if you hear noises in a specific gear, that gear’s teeth or synchronizer could also be worn or broken.
Sources inside the transmission that may cause noise:
- A worn-out synchronizer
- The gears on the speedometer drive
- Misaligned transmission
- A worn or broken input shaft bearing, if your transmission makes noises only in neutral (sometimes a bumping sound)
- Worn-out gears
- Output shaft pilot bearing issues
- Metal shavings in the oil
Some noises that seem to come from the transmission are actually coming from an outside though possibly related source. For instance, if you hear a thumping noise when you accelerate or decelerate, check 1st for these issues before you blame the transmission:
- A loose or broken engine or transmission mount
- A worn or broken drive axle inner CV joint
- Problems with the differential case
- Noises that manifest when turning might point to a problem with the CV joint. knocking noises when driving at low speeds may come from the differential case or the CV joint.
- The Transmission Makes a Grinding Noise
Problems with the transmission may also be revealed through a grinding noise. A grinding noise might come from clashing gears. The clashing might happen due to linkage issues like wear or need of adjustment. Other potential sources may well be a worn or broken synchronizer, shift fork, or rail and bearing shafts. If you can hear the gears clashing only when downshifting, the problem might come from the synchronizer (too much play at the output shaft end). However, a grinding noise can also come from a dragging clutch.
- The Transmission Jumps Into Neutral
This appears to be a common problem on worn-out transmissions. You shift into gear, and the transmission jumps out of gear. Once again, there might be other causes for this problem, besides a worn-out transmission. A common problem is a worn out, stretched, or maladjusted shift linkage. A stretched linkage may be caused by a broken engine or transmission mount. an external linkage can wear out or become loose and maladjusted, causing the transmission to jump out of gear. look for rust and binding. you can attempt to adjust the linkage. however in most cases, you’ll need to rebuild or replace that part of the assembly.
You may be dealing with a weak or broken spring within the shift rail. In an internal shift linkage, the spring is part of the spring-loaded ball that locks the transmission into gear. If the ball slips out of the notch, the transmission can jump out of gear. Also, you may be dealing with a worn-out pilot bearing (the gap causes the input shaft to vibrate, which causes the shift forks or synchronizers to move). You may have issues with a worn synchronizer or shift fork assembly or other internal parts.
Other potential causes to keep in mind:
- Loose or misaligned transmission (possibly after service)
- Misaligned clutch housing
- Loose shifter cover
- Worn-out gear teeth
- It’s hard to Shift Gears
This problem happens when you find it hard to maneuver the shift lever from one gear to another. Usually, this points to a problem with a loose linkage, worn shift cables or worn bearings.
Other causes for a hard-to-shift manual transmission include:
- Worn or loose internal parts (shift fork, levers, shafts)
- Low oil level (or the incorrect kind of oil)
- Misaligned transmission
- Synchronizer issues
- The Transmission Is Stuck in gear
You may notice that you just cannot get the transmission out of gear. This symptom might indicate:
- Low oil level or the incorrect type of oil
- Problems with the linkage or shifter assembly. search for maladjustment, or wear or damage to rods, bushings, or shifter arms.
- Internal components: shift rail, detents, forks or a stuck synchronizer sleeve
- Worn-out or broken drive gear teeth
- A stuck shift rail
- Misaligned transmission
- The Transmission will not Get Into Gear
When you have trouble getting the transmission into gear, examine the shift linkage for adjustment, looseness or damage. However, keep in mind that failure to get into gear may also be caused by the clutch, if the clutch is not fully releasing or has alternative issues. The clutch may need adjustment.
- Leak From the Transmission
Manual transmission leaks are often caused by:
- Bad or worn-out seals or gaskets
- A broken case or part
- Loose bolts
To verify that a leak exists, first, check the transmission case and oil level. If it leaks after you just replaced the oil, you may have put too much. Consult your local Eagle Transmission technician.