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Toyota Surf quits shifting when car is running

I live in Moz, Africa. I have a 1994 Toyota Surf Hilux. Lately the manuel gear has quit shifting while the car is on. I can correct it by shutting the car off and then it shifts perfectly. This started out as an intermittent problem but is getting increasingly worse. It happens every day now. Trust me, this is very dangerous not to be able to shift while in African traffic. HELP! Can anyone help me figure out what is the problem? I don’t want to take it to a mechanic here because they aren’t usually trustworthy - they will fix all kinds of problems that I don’t have and I can’t afford to have my car tied up for weeks with no results. I have a friend who might be able to fix it if we can ascertain the problem but it is pretty confusing as to what the problem might be. The clutch was replaced a year ago.

This will be tough because you really need to find someone who is trustworthy and has a good understanding of the mechanics of your car, but you tell us that there is no one that meets your needs.  

Let's start with a few questions:

How many miles are on the car?  Have long have you owned it? Has anyone checked and/or replaced the transmission fluid since it was new?  How about the clutch?

Please clarify. When you say it quits shifting. Do you mean the shift is hard to move and shift the transmission out of or into another gear? A sign the clutch isn’t disengaging. Or does the shift lever feel like it it disconnected from the transmission?

We know that the clutch if failing to disengage, but our only clue is that it was originally intermittent.

A clutch may fail to disengage for several reasons:

  1. Failed throwout bearing, pivot, or lever arm inside the bell housing. None of these, however, would be expected to be intermittent at first. If any of these fail, the clutch pedal should be very easy to press down.

  2. Foreign material between the clutch disk and the pressure plates. The most common foreign material is clutch facing material that is coming loose from the clutch disk, as a result of severe wear or abuse.

  3. Rust, causing the clutch disk to freeze to the shaft that it slides on, holding it tight to the flywheel. I had this happen on a Volvo once after my wife drove through deep water.

  4. Failure of the clutch disengagement system, which in your case is likely hydraulic rather than a cable. Does the clutch pedal pressure and stroke feel normal? There will be a master cylinder behind the clutch pedal arm and a slave cylinder down on the bell housing. This system likely shares fluid with your brake system, but if it has its own fluid reservoir, make sure the level is up where it should be. Examine both cylinders and see if either one appears to have been leaking. Because the clutch is fairly new and the problem was initially intermittent, this is my prime suspect.

The car has 140,000 kilometers on it. Admittedly, it has seen some pretty rough roads. Roads in Africa are full of pot holes. The fluid level for the master cylinder and the slave cylinder are not low and there appears to be no leaking. When I am driving, and try to shift, it absolutely cannot be forced to shift. It won’t go in any gear, including reverse. It grinds when I put it in reverse only but not in the other gears - there is no noise, they just won’t budge. I turn off the car, and immediately I can put it in any gear. I start the car, drive, and then I can’t shift into the next gear from what I started out in.

I might add that I have had the car for four years. I have driven through many a puddle during the rainy season but the rainy season has been over for a couple of months. The transmission fluid hasn’t been checked or changed since we have owned it.

It sounds like the clutch master cylinder is leaking internally. When this happens and you step on the clutch pedal there’s no hydraulic pressure produced to operate the slave cylinder to disengage the clutch. So basically it’s like trying to shift the transmission without stepping on the clutch pedal.

Locate the clutch slave cylinder on the transmission and then have someone step on the clutch pedal. If the slave cylinder doesn’t operate the clutch master cylinder is leaking internally and requires replacement.

Tester

It sounds like either the master or slave cylinder is leaking internally, allowing fluid to pass by the piston in the cylinder, thereby rendering the clutch release system inoperative.

You can shift it when the engine is off because there is no load on the gears even with the clutch engaged.

If you have a friend to help, see if you can verify whether pushing the clutch pedal in is causing the fork that moves the release bearing to move. .

That seems like a logical solution but how can that be when it works sometimes? It is an intermittent problem
that is getting worse.

When the clutch is desengaging correctly, pay close attention to where the pedal starts getting stiff. When the problem arises see if the pedal gets stiff lower down. If so the clutch master cylinder is leaking internally when hot.

To test to see if the problem is heat related, pour ice cold water over the clutch master cylinder when the problem is occuring and see if that alleviates the symptom for a time. Also try pumping the clutch pedal a couple of times quickly before you try shifting into the next gear (with the pedal down of course).

I too suspect you will need a clutch master cylinder. You might replace the slave cylinder at the same time as they usually wear out in unison.