Does a clutch behaviour get slowly worse over time? What can I check for difficult gear selecting?

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My 80 is really difficult to get into lower gears when cold, and has started recently doing a similar thing when hot. I don't know how to double-clutch, etc. when changing gears but sometimes I get 3rd gear with no effort and other times it feels like it 'catches' twice when I move the gear lever to select it.

Can the gear lever or associated parts go bad and cause sloppy/bad selecting? It's a h150f 5-speed box.

Last time the gear oil was renewed was about 2 yrs ago, and the box is a rebuilt one fitted about 5 years ago.
 

micruz60

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Bushing at the bottom of the gearshift lever.

or

Clutch adjustment at the pedal, or at the slave cylinder-(may not be adjustable)
 

Dave 2000

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First I am unsure if your model has an adjustable slave cylinder, if it does it will be the first I have seen on an 80, so the rest of this post is from a mechanics point of view, and it is unlikely the clutch is giving issues anyway, your explanation of the problem is indicative of a common problem on these gearboxes.

The 80 gearbox has been available in at least three different versions, each one upgraded invariably to address synchromesh issues, the synchromesh allowing the gears to mesh without double declutching. The fact that your symptoms alter then synchromesh is almost certainly the issue. There has been a lot said about this and I have come to the conclusion that you cannot get around it, and if you do by a rebuild it will be at best short term only.

One of the contributing factors to the problem is the oil used, whilst the hypoid additive is great for differentials it is not for the synchro rings in the gearbox, and the oils available today have a considerable amount of hypoid mixed in. So I decided to spend some time to see what other people were using long term and checked out their findings. The best option is a GL4 oil, yes it has hypoid and the previous versions (GL3 or GL2) have less hypoid but they are generally not available. A shall we say 'discussion' with a Toyota parts dealer had him telling me GL5 was 'better' because it was the latest version, of course it is virtually all hypoid. I also emailed Castrol agents in both the UK and Australia, and they recommended different oils for the 80 gearbox WTF!

So drain and refill with EP 75/90 or 80/90 but graded as GL4, I have fitted a second hand gearbox in my 80 and that oil is what I have used over the last few years with minimum issues. Using a fully synthetic gearbox oil prevents the synchromesh cones 'gripping' so the gear you re trying to select will not align correctly, (the synchromesh's 'job' is to bring individual gears up to the same speed so they mesh cleanly) so if the oil is too 'slippery' if that makes sense, the result is difficulty engaging gears, temperature of the oil also affects this problem. So in the morning if you cannot engage first then try second, then move smoothly from second to first.

So unless research/experience from others counters my opinions, as in their has been major changes over the last 5 years or so then give them some thought.

Double declutching.

Having driven heavy goods vehicles in the past some of them very old with NO synchromesh, means double declutching was the typical method of changing gear.

So clutch down pull out of current gear into neutral and release clutch, depress clutch again and engage next gear and of course release clutch, it really is that easy but when going down the gears make sure you are going slow enough not to end up over revving the engine. I found this was needed on second gear on my old 80 gearbox, you will find the shifts easier and smoother, and certainly much easier on your gearbox.

I won't go into not using the clutch at all to change gears, that is for another day, but it can be done.

Hope this helps.

Regards

Dave
 
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micruz60

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Good point ^^ Synchros , and gear oil from dinosaurs.
 

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