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Home > Help Needed / General Tech Chat > Non selection of first gear (or jumping out) after gearbox rebuild

ricsdad

45 Posts
Member #: 9406
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Tadley, Hampshire.

I am hoping someone can point me in the right direction with this very disappointing problem. The gearbox in question is in an ERA Turbo Mini. I like to do things myself but I am very slow, methodical and exact - my aim is to preserve the ERA as it left the factory - she is more for show than go these days!

Since I have owned the ERA it had always had a gear selection problem diagnosed as the split bush in the reverse gear coming out an obstructing the gear selector? (Did not really understand why or how but I knew it needed replacing. There were no other problems with the gearbox, no noises, no jumping out of gear - and NO oil leaks it was just difficult to get first and reverse plus travel across the gate was stiff. The box had only done 25,000 miles so I did not anticipate any issues due to wear.

I have never done a gearbox before, I rejected all help from my many Mini friends to replace the reverse gear for me (I had purchase a new old stock item already) I could not entertain the possibility of putting the whole lot back together and in the car only to find a problem requiring removal and strip down again.

I selected a well respected local transmission company who is used by most of the local garages. It did not occur to me that perhaps he had not done a Mini gearbox recently, he had all the equipment to strip, clean and reassemble with new reverse gear. seals and gaskets.

This story is littered with clues as we go along as to what was to unfold........

5 days later I collected the box all clean and apparently correctly assembled - as he gave me the box he pulled at the gear selector rod - as if demonstrating how it now moved freely.

Having never done a gearbox before, I have never mated the gearbox back to the block, I asked the transmission guy "What sealer do you use with the gaskets" The answer I do them dry! I asked "The half moon crank seal - which way round does it go?" He told me the wrong way!! I did check before I put in in - I did get that right.

I assembled the engine and the gearbox, I wanted to check if he had used a new copper washer on the drain plug, having undone it - i could not even get it finger tight because the threads were stripped - they were good before - I know I did the last 2 oil changes. Lucky escape because I could helicoil it before the engine went back in the car.

Put the engine back in the car - filled it with oil and it leaked badly from both end plates and possibly the diff cover too - seems his method of doing the gaskets dry does not work! Thats ok I thought I can renew the end plate gaskets in the car once I test the operation of the gearbox.

I did not expect a problem testing, I knew the gearbox was selecting gears, the gear change was smooth and precise - now I could be wrong here - but it seems that instead of a nice straight "H" shape for gear selection the position of the gear leaver for 1st appeared to be forward and to the right a bit - so a small amount of diagonal movement and not just straight forwards.

So the day finally arrived for the test. Start the engine, select first, bring the clutch up slowly like a learner - no drive - weird. Select neutral raise clutch I can hear by the small change in engine note that the clutch is working. Engage second - we have drive, third - drive, 4th drive. Reverse easy positive selection - drive. Back to first still no drive. Then I try select second then forward to first - we have drive! Briefly before it jumped out. Tried a few times carefully always with the same result.

So to summarize - Easy gear selection 2,3,4 and reverse all select easily have not driven it so I am assuming they will stay in. First will only select if you go second then first quite firmly. Jumps out of first gear.

The rod change is correctly attached with new rubber mountings.

My dilemma is I can have no confidence that the "professional" who stripped and rebuilt the gearbox is going to be capable of fixing it. I really need to know what he has assembled incorrectly to cause this

Can anyone confirm if it could be an assembly problem, or perhaps damage to the selectors caused by the original reverse gear problem. In any event which bits should I inspect or replace?


Tom Fenton
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15251 Posts
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Fearless Tom Fenton, Avon Park 2007 & 2008 class D winner

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TM legend.

Rotherham South Yorkshire

Has he put the 1/2 (and also reverse) synchro boss the wrong way around on the synchro hub? It will fit either way round but sits biased over to one side. Ask me how I know!! Have you a photo of the box internals before you installed it?


On 29th Nov, 2016 madmk1 said:


On 28th Nov, 2016 Rob Gavin said:
I refuse to pay for anything else


Like fuel 😂😂


ricsdad

45 Posts
Member #: 9406
Member

Tadley, Hampshire.

Hi Tom, thank you for your reply - I have a picture of the box before being professionally rebuilt - but unfortunately not after. I do have another here to compare it with when I take it out again. Some one else agrees with you that the gear has been put in the wrong way - would also explain the position of first being slightly diagonal now!

It is what its is, and it is not going to fix it's self - at least now I understand why and can avoid it on the second rebuild!

Thanks again


theoneeyedlizard

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The Boom Boom speaker Police!

Essex

Would reverse still be ok with the 1-2 selector the wrong way around?


On 28th Oct, 2019 Tom Fenton said:
Has he put the 1/2 (and also reverse) synchro boss the wrong way around on the synchro hub? It will fit either way round but sits biased over to one side. Ask me how I know!! Have you a photo of the box internals before you installed it?

In the 13's at last!.. Just


ricsdad

45 Posts
Member #: 9406
Member

Tadley, Hampshire.

I have discussed this problem with the "gearbox specialist" alarmingly he did not seem to understand - "The centre of the synchro hub is the wrong way round" He was focused on the whole synchro hub saying that it could not be the wrong way around.

So just to be clear the centre of the synchro hub is the sliding portion that has 3 dog slots in it and 3 balls and springs. I have read that it is off centre and has a deeper central flange one side to the other. Being the wrong way round means the throw is not great enough and the specially shaped teeth are unable to engage sufficiently to mesh.

He has suggested that I need to test the first gear selection with the remote rod disconnected from the box - cant really see the point of this as it is hardly a real test of the linkage

Thanks again for your help!


Tom Fenton
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15251 Posts
Member #: 337
Fearless Tom Fenton, Avon Park 2007 & 2008 class D winner

&

TM legend.

Rotherham South Yorkshire

http://www.minispares.com/product/Classic/...spx%7CBack%20to

If you look at the top down photo of the box, you can see the reverse teeth on the 1/2 synchro hub are offset to one side.
Its very possible to assemble this backwards, so the offset is the other way. The selector fork works on the sides of this gear.
With it assembled (wrong) the synchro hub doesn't sit centrally.
In the photo you see an equal gap side to side. When assembled incorrectly the synchro hub is biased to one side.
In practise as you correctly say this doesn't allow 1st to engage properly.

I know all this as I'm sure you have guessed, I once many years ago built one the wrong way around.


On 29th Nov, 2016 madmk1 said:


On 28th Nov, 2016 Rob Gavin said:
I refuse to pay for anything else


Like fuel 😂😂


ricsdad

45 Posts
Member #: 9406
Member

Tadley, Hampshire.

Hi Tom, thank you for your very clear explanation - I guessed that you had learnt this from bitter experience - I doubt that you are the only one! I will eventually finish this thread with the "autopsy"

Edited by ricsdad on 29th Oct, 2019.


Rod S

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5878 Posts
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Formally Retired

Rural Suffolk

Here is a slightly more obvious photo of the offset Tom mentions.



I took this absolutely ages ago an a gearbox I was about to dismantle because I too, in the dim and distant past, had put one the wrong way around.

In my case it was the 3/4 (left of photo), not the 1/2/R (right of photo) - photo is with both the correct way around.

If it turns out to be this, then your gearbox expert is totally incompetent because on the 1/2/R sleeve the chamfer on the teeth show exactly which way around it has to be to mate with the reverse idler gear.

However, like theoneeyelizard, I'm not sure that reverse would work properly if the sleeve was on backwards, and it might be very difficult to actually dis-engage 2nd gear.

However, the only way to know is a top view of the box in that area.

Any chance of getting one of the cheap eBay smartphone borescope adapters (or similar) in through the dizy hole before a major dis-assembly ???

I've never tried one myself but some people claim success with them.

Edited by Rod S on 29th Oct, 2019.

Schrödinger's cat - so which one am I ???


graemec

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Carnforth, Lancs

I think ricsdad is nearer the mark in that the centre of the synchro hub is potentially the wrong way round, not the outer.


Paul S

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8583 Posts
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Formerly Axel

Podland

I had a load of problems with gear selection once. Turned out to be a problem with the shifter, a cheap quickshift rip-off.

I suggest you eliminate that possibility before pulling the engine.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."


Yo-Han

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North of the Netherlands

Do you have an endoscope?
Not sure if you can ge a proper look at items mentioned via sump plug.
But might save you from possibly pulling the engine without need...

Dazed and Confused....

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