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Gearbox Again! 1St Gear Sometimes Doesn't Engage And 3Rd Somtimes Hard To Find

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#16 Spider

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Posted 03 December 2021 - 05:11 PM

Do you guys have any more tips for me? I planned on taking the engine out the 20th of december.

 

I've just read back over the thread and given the time frame since we last exchanged on this, can you kindly re-cap;-

 

       What it's doing / not doing now, and

 

       What you've 'fixed' / changed / found

 

in recent times ?



#17 gazza82

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Posted 03 December 2021 - 05:12 PM

for first gear, it sometimes helps going in 2nd but not always. What is the cause of that?


1st doesn't have synchromesh ... likely to always crunch if going direct to 1st on the move.

#18 Moshtaraq

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Posted 03 December 2021 - 05:13 PM


1st doesn't have synchromesh

 

Then I have a special limited edition that does have a synchroring :D



#19 Moshtaraq

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Posted 03 December 2021 - 05:21 PM

Spider,

 

I'm kind of married to my work so I've only driven it twice in the last month.

  • third gear: I seem to overshoot it to the right as it is slightly going into the reverse channel. As I mentioned, I encountered this in a VW T3 and we replaced a knuckle that supports the gearlever. Never took a mini gearlever apart so don't know what it looks like.
  • 1st gear is sometimes impossible to engage when stationary. I seem to remember that when throttleing a bit, it engages. Going into another gear first did help but lately less. (I don't know if any of this makes sense or is useful)
  • When I bought the engine, there were no synchro's left on it so I did a rebuild with a minispares kit and put a new 1st and 2nd gear in it cause there were teeth missing (the ones that engage with the slide hub)


#20 gazza82

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Posted 03 December 2021 - 07:55 PM

1st doesn't have synchromesh


Then I have a special limited edition that does have a synchroring :D

Or worn synchro?

#21 Moshtaraq

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Posted 03 December 2021 - 08:01 PM

 

 

1st doesn't have synchromesh


Then I have a special limited edition that does have a synchroring :D

Or worn synchro?

 

would surprise me since it's a year and 2k km old



#22 Spider

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Posted 04 December 2021 - 02:40 AM

 

Spider,

 

I'm kind of married to my work so I've only driven it twice in the last month.

  • third gear: I seem to overshoot it to the right as it is slightly going into the reverse channel. As I mentioned, I encountered this in a VW T3 and we replaced a knuckle that supports the gearlever. Never took a mini gearlever apart so don't know what it looks like.
  • 1st gear is sometimes impossible to engage when stationary. I seem to remember that when throttleing a bit, it engages. Going into another gear first did help but lately less. (I don't know if any of this makes sense or is useful)
  • When I bought the engine, there were no synchro's left on it so I did a rebuild with a minispares kit and put a new 1st and 2nd gear in it cause there were teeth missing (the ones that engage with the slide hub)

 

 

OK thanks for that - Married to yr work - all too familiar story these days !

  • 3rd Gear - almost certainly, this is a shifter issue.
  • 1st Gear - nearly always, shifting in to 2nd, then 1st, it flys in. I'm at a bit of a loss here, the only thing that does come to mind is the 1st / 2nd gear Synchro Hub is worn and the outer track is leaning over, before sliding. I note that you've replaced the Gear itself, if this was a new gear, I'm wondering if it's an after-market one or genuine ? If non-genuine, that may have something to do with this issue. One other thing that's come to mind is if the Syncho Hub has been apart, it's possible that one (or more) of the Detent Balls are missing. If the Spring is in there, that'll grab on the outer track for sure.

 

 

 

for first gear, it sometimes helps going in 2nd but not always. What is the cause of that?


1st doesn't have synchromesh ... likely to always crunch if going direct to 1st on the move.

 

 

Yes, from 1959 to 1968, the gearboxes in our Minis only had Synchromesh on 2nd, 3rd and top gears, however every gearbox from around March 1968 has also had Synchromesh on 1st gear too.



#23 Moshtaraq

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Posted 20 December 2021 - 07:06 PM

That little bushing above the connectingrod is completely gone, the nut was even missing. Does this solve the third and fourth issue? By having no set reference, the shifter can move too much and go into the reverse slot?

#24 Spider

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Posted 20 December 2021 - 11:58 PM

That little bushing above the connectingrod is completely gone, the nut was even missing. Does this solve the third and fourth issue? By having no set reference, the shifter can move too much and go into the reverse slot?

 

Yeap, gotta have a steady bar !



#25 Moshtaraq

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Posted 23 December 2021 - 11:26 AM

Gonna get a new bush tomorrow when the engine goes back in (hopefully). The problem with first is that when the teeth exactly line up, it's like pushing against a wall. Moving the diff-side just a bit allows the teeth to engage properly. Is this by design or is there something that should prevent that.

#26 Spider

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Posted 24 December 2021 - 07:44 PM

I should hope that they can 'line up', at least there's the same number of dog teeth on both sides, not that there was any different types.

In order to allow for the hub outer track to slide over, the track and the gear dog teeth need to be sychronised.

 

When you shift gears, the action is something like this;-

 

The selector fork pushes up against the hub,

The hub outer track, held in place on it's detents, will slide on the mainshaft in the direction it's being pushed,

The inner track of the hub then puts pressure on the baulk ring,

The baulk ring then will 'bite' on to the cone on the gear and start to spin the gear (which free wheels on the mainshaft), at the same

            speed as the hub, but some slippage can still occur between these parts, the ears on the baulk rings too encourage this action,

At the break away point where the force from the selector fork overcomes the detents, the dogs between the gear and the hub are fairly close to each other,

As the outer track breaks away, it tends to 'fling' in the backlash of the selector mechanism, and 'look' for engagement over the dogs of the gear,

To help with that engagement, the lead teeth length and angles of the outer track are varied ever so slightly between each other, this helps them align,

Finally, the outer track then snaps in to it's selected dentent and 'holds' gear.

 

This action firstly works best when the assembly is rotating. As there needs to be movement between the gear and hub, the ratio of the gear itself can come in to play here, with a smaller gear having less leverage on the Laygear and Drop Gears and Clutch Plate (as these parts too needs to move with the gear), and so will go in easier than a larger diameter gear. Also, when stationary, any rolling of the gear train to align the dogs is purely from the pressure on the selector fork alone. This is why 1st can be hard to select.



#27 Steam

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Posted 24 December 2021 - 09:25 PM

Not sure if this has been mentioned but first and third can be hard to select if the gear shift assembly is out of position or misaligned. I had this issue and it was the gear shift mounting bracket had gotten bent.







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