Manual Transmission Diagnosis
Transmission Repair Manual
Last week’s post was about manual transmission diagnosis and repair. This week I will dive a little deeper into actually diagnosing problems.
Surprisingly, information about manual transmissions is not that easy to find on the Internet. That is why I decided to post a few more times about this subject.
But keep in mind the most accurate information is available in your vehicle specific auto repair manual. This should list the most common problems associated with, your transmission and/or trans-axle if you have a front wheel drive car.
Here is also a Amazon link for the how to rebuild manual transmissions
Many problems that seem transmission related may actually be caused by defects in the clutch assembly differential or drive shaft areas. Check these areas along with your standard diagnosis, particularly if you are considering removing the transmission for further inspection or repair.
Visually inspect your manual transmission
RWD Manual Transmissions
Before you start grabbing wrenches and removing bolts it is always recommended to perform a really good visual inspection. Here are five of the things that you should check for.
1) Check for looseness of the transmission by pushing up and down on the unit from the tail shaft (a pry bar in the right place makes this easier). Take a look at the transmission mounts to see if the rubber separates from the metal plate. If the case moves up but not down. The mounts may require replacement.
2) Check for lubrication leaks at all of the gasket and sealing areas. On manual transmissions the output shaft seals or rear trans seal where the front drive shaft yoke slides in is prone to leakage. So don’t miss taking a look at this tail shaft seal.
3) Check the case body for signs of porosity that show up as a leak or seepage of lubricant. Aluminum housings can have small imperfections that allow transmission fluid to leak out of areas that are not sealed by gaskets.
4) Move the clutch and shift linkage around the gate and check for loose or missing components. Cable linkages should have no kinks are sharp bends and all movement should be smooth. Lubricating and adjusting the linkage can alleviate binding problems.
5) Manual transaxle’s with the CV joints or tripod joints should be checked for lubrication leakage. Older vehicles may experience cracking of the rubber boot that allows the heavy grease to be thrown out of the joint while it is spinning.
It is also possible for the band clamp to loosen and allow the grease to escape. Finding these problems early can save you from replacing the joint.
Transmission noise
Many manual transmissions, complaints will stem from noise during operation. Once again be certain the noise is not coming from other components in the drive train.
Internal Workings
Unknown unusual noises may also be a sign of trouble in the engine or transmission mounting system. Inspecting all engine mounts along with the transmission mounts should be done early in the inspection process.
A test drive with the vehicle’s owner is recommended. If during a test drive, you hear a noise you suspect is coming from inside the transmission or manual transaxle bring the vehicle to a complete stop. Then disengaged the clutch.
If the noise stops with the engine at idle and the clutch disengaged the noise is probably caused from spinning parts inside the unit. If the noise occurs when the clutch is disengaged and the transmission is in the neutral gear.
The problem may stem from the input shaft bearings. When your foot is off the clutch pedal and the transmission is a neutral. The only spinning or moving parts would be the input shaft and clutch components.
Detailed and extremely helpful ladder diagrams in quality auto repair manuals will help guide you through the steps of not only diagnosis but also the repair.
The service manual also indicates where special tools will be required for disassembly. Knowing what is involved in the repair should be looked into before removing the transmission from the vehicle.
Return to the homepage and see the latest posts. This next link takes you to more auto repair information.
Mark Gittelman is an ASE Certified Automotive Master Technician With more than 24 years experience in the auto repair field.
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Hi Mark. I just bougth a 2001 Toyota Hiace LWB van. I noticed that when changing from 3 -4 gears there is a violent shutter. This only seems to happens if i try to change from 3-4 doing 30-34mph. If i get the van to 34mph in third and then change to 4th gear the shutter is not as bad, if i wait to 36mph or a little more the shutter dose not happen. It seems the problem is only between 3rd and 4th. The guy i bought if from said that driving a van is not the same as driving a car and that you need to give it a bit more revs. I am a bit worried that it might be the fly wheel or clutch or even the gear box.
The van drives well apart from this, but when it happens it is really violent until I get past 35-38mph. any ideas what it might be. I could take to a mechanic but I would like to know what im talking about before giving it to someone who might take advantage.
Brian.
Hi Brian: Its hard to say exactly what your problem is with out an actual road-test. But from the way you describe your symptoms it would seem an inspection of the drive-line would be in order. Checking for any play from the out put shaft of the transmission would be a good place to start. Also sometimes when you get a shutter in only one gear range it can be an indication of an internal problem inside the transmission.
Mark I had an auto guy look at it to day. He took it for a test drive and it sounded fine. in the end he put it down to thw way i was driving it. He told me that driving a van is not the same as a car and that I needed to give it a tini little bit more revs. Rigth enough, it did sound ok when he was driving. Better safe than sorry. so at the end of the day what I think he was saying was, I have to stop driving like a girl (grin) thanks for your reply.
Brian.
Hi Mark got another question for you. would a set of heavy duty jump leads do to wire my van battery to my leisure battery and also my 500w inverter to my leisure battery. the price of battery cable is a rip off.
my inverter comes with 50w cables so if i got some heavy duty leads do you think they would do the job?