Jump to content

Mk3 GT6 Second Gear


Ingieuk
 Share

Recommended Posts

hope i wasnt wrong about he 2nd hub offset  read it but cant find where that was now !!! Grr,  the small groove in the hub spline is a design to stop it jumping out of gear 

in as much the sleeve gets locked when under power  its not a wear groove 

there is only 2 ways to fit this stuff so when you have tried all six  it will work nicely   !!!!!!!!!

Pete

Link to comment
Share on other sites

1 hour ago, Ingieuk said:

I do agree it's an odd design choice and therefore unlikely.

It needs to be right this so it sounds like box is coming back out agin😔

I have identified through photos the 1st/2nd syncro hub is the opposite way around to what it was before I stripped the box. You can see from the wear groove if you look closely at the pre strip photo below compared to the post strip one earlier in this thread. Given the hub boss is not even I wonder if that would make a difference. 

Either way time for the box to come out again. 

DSC_0216.JPG

Think you have the smoking gun right there......

Bit of an annoyance that rectification means a complete strip down. Do not be tempted to reuse the circlip under 3rd gear (though you may not need to disturb it) - it will break later if you do.

Nick

Link to comment
Share on other sites

No worries Pete, I should have been more careful noting which way round things were when I took it apart! 

I hope so Nick, I really do. 

I'm just waiting for some parts from Rimmers (new gasket set, new circlips, new nyloc) before I strip the box totally. Having got the box out and rear extension off the reverse idler distance piece measures 23.68mm. This is close enough to the 23.98mm original size of the three rail for me. There is no binding on the 1st gear to speak of. The replacement idler is of the same size and teeth as the original. The actuating arm is a slightly loose fit in the idler groove, but can't really do much about that as they are no longer manufactured. 

Things are going to slow up a bit as I'm staring down the barrel of three or four unexpected night shifts at work. This means my precious 90min a night in the garage after our 1 year old is in bed has gone. Never mind! 

Link to comment
Share on other sites

we have all been there ,, you note things put it in the grey matter bank , no sketch or photo , thats  easy I will know .....much later ,,, how the heck did that fit ...  its  the red mist 

and blank looks  ....then you browse the manuals and they dont tell you the one thing you need to know   happens a lot 

Pete

Link to comment
Share on other sites

It is a relief being able to take unlimited numbers of photos (even if you always miss the key ones). Not sure what I'd have done if I had to get them developed. I certainly wouldn't have taken as many! 

 

Managed 40min this morning and have got the box stripped again. I'm tempted to replace the syncro rings whilst I'm in as the new ones I have leave a 1.2mm gap between the engagement teeth on the gear cone and the syncro ring teeth on new syncros and nearly 0.5mm gap on the old ones. 

I'll try and get a bit better accuracy than 0. 5mm but it's not far off. 

Once the mainshaft and input shaft are back in I'm going to put some thick Ali plate over the reverse idler shaft to hold the Bush flush and check the 1st gear and syncro hub clearance. 

Link to comment
Share on other sites

it is daft when you can do things almost blindfold but when asked to think about what goes where it all goes into a muddle 

this just shows with a bit of guidance a bit of mis guidance all thrown in for the love of DIY classic repairs you can end up with a solution

you would never have contemplated before they invented tea and bacon butties   

this is looking a good job after  the initial what the !!!  

i agree the gap when  the old ring is rung on is a bit close at 0.5  new rings should be ok its if some muppet has turned them in a lathe chuck they are made lobed 

if there is any wobble when rung on ( being a hand push and twist ) they are going to e useless , they should acheive a good grip no rock/wobble

remember the mainshaft rotation drives the synchro as you change gear the ring has to rock over 1/2 tooth , spin the clutch disc up/down to speed and once sync'd allow the change to complete all in the blink of an eye  ...amazing really .

Pete

Link to comment
Share on other sites

Little update. 

New syncro rings on, new 3rd gear circlip, box back together including rear extension (laygear shaft still not fitted). 

Even with the 2nd syncro the right way round the reverse idler is still catching, albeit not as much. It seems the neutral point for the reverse idler is too far towards the front of the box. It's a few mm off the distance piece that keeps it out of 1st. If I push the selector arm so the idler is hard up against the distance piece it sits nicely in the gap. So it seems the reverse arm needs adjusting? 

However from what I've read the adjustment most people make is to bend the arm inwards towards the mainshaft (perpendicular to mainshaft). Whereas I seem to need to push it towards the rear of the box (parallel to the mainshaft). Any ideas?

I may also remove the mainshaft and try the original reverse idler again. Current one is a pattern part from rimmers. 

Link to comment
Share on other sites

take care with a little bending, for aft is not adjustabled other than spacers /bending as you see it , the lever is quite substantial but this does seem to cause problems on some boxes 

and there needs some idea where the top cover is going to position the lever in neutral all a bit airy fairy 

the engagement  left right towards the mainshaft is set by screwing the bolt/post more on or off the lever , book say on till one thread shows through but its adjustable

 

Link to comment
Share on other sites

It may be irrelevant but I had to belt the hell out of our spit reverse lever(Spit single rail internals into 3 rail box) to get the selectors to align, in retrospect the issue was I used the single rail longer reverse spacer, but another requirement of the 4 syncro Mk4 3 rail box was a washer on the reverse selector rod to stop the selector going too far forward. not having needed to strip my Vitesse box I'm not sure if the Vitesse 4 syncro box has the washer.

Link to comment
Share on other sites

  • 2 weeks later...

Box is back in with a new reverse lever (NOS from Canley Classics). Not turned the engine over in anger yet so not sure of the outcome yet with regards the reverse idler. It looked like there was clearance but we shall see.

In the meantime I've managed to strip the bleed nipple on RHS caliper (dissapointed in myself!) so there will be no road testing until that is sorted!

 

Link to comment
Share on other sites

On 15/06/2020 at 22:36, Ingieuk said:

No worries Pete, I should have been more careful noting which way round things were when I took it apart! 

I've finally started to bag and label stuff, about twenty years too late for my cars, but the grey matter no longer holds the same data as it used to.

I really hate suppliers who will supply a part - usually a bolt or nut - and won't give the dimensions, just their own part number, so that I can't check if I have any already... then when it arrives I find half a dozen.

Link to comment
Share on other sites

  • 2 weeks later...

So... 

Back on the road (briefly), I dared a 2 mile drive with a known poor rotoflex coupling as I had to know if the gbox rebuild had worked. I'd like to get all the interior back in before starting on the next job! 

All is smooth and quiet, except... 3rd to 2nd. There can be a real crunch. Oddly if you are slowing for a roundabout (so going a but quicker) it slots in lovely, but go from 3rd to 2nd at lower speeds and there is a bit of a crunch. Its a bit of a 'fake' test as in normal driving you dont do this, but it still shouldn't do it. 

I wonder if there is an issue with the 2nd gear syncro ring. Doesn't affect 1st to 2nd or 2nd to 1st, both lovely changes. 

Is it a case of the new syncro rings bedding in? As it's reasonably okay I'm minded to refit all the interior and just be a bit careful driving it and see if some miles on the gearbox help. I need to change the rotoflex couplings before I drive any distance anyway. 

Maybe then a winter job to get the box back out check the rings (put old one back in?) and fit the new reverse operating lever I've managed to source. 

 

Any thoughts? 

Link to comment
Share on other sites

It might improve with use.  Bit of a long shot.  Hub release pressures a bit light maybe, or just not a very grippy synchro.  Might improve when the oil gets properly warm.

It's a real minefield.  New synchros aren't always great, decent used ones getting rare, and the cone surface on the gear can be a factor too.  You have to try the baulk rings on, see what gap is left (more the better in general), but also, push and twist them together.  A pair that is going to work well together will bite as you twist - it's difficult to describe - almost a squeak - but more a sensation of grip and friction than anything you can actually hear.  If they just slide, they won't work well.  I like to try a few and see.  I will choose one with good bite over another with less bite even if it has more gap.  Have seen new ones that are slightly out of round so have a great gap but minimal bite.

What gear oil are you using?  Can have a quite a big effect.  Redline MTL or MT90 works quite well for that I've found.

BTW on mine GT6 box I chose hub release pressures on the high side.  Synchro works well but it is a bit notchy so far.  Not as quiet as I would like either.

Nick

Link to comment
Share on other sites

3rd to 2nd is having to sync more revs than 1-2   and with a new clutch disc it may need the fuzz wearing in to clear nicely , i would give it some driving once the rota is fixed and see if it improves 

make  firm changes , if you hesitate through a change the rock over will let go and you crunch ... thats dont rush but dont release stick load during a change , if you know it might clash 

you can make it worse if you tickle it .

but a clearing clutch is fundamental to disc spin up synchronising 

pete

Link to comment
Share on other sites

give the throttle a blip on the way down works for my Dolly on a worn box so should work on a rebuilt box, not a full double d'clutch but just a little blip, on the way up not to fast or slow but positive movement between  2 & 3, works for me no racing changes, eventually I'll pull the box and fix!

Link to comment
Share on other sites

10 hours ago, Nick Jones said:

It might improve with use.  Bit of a long shot.  Hub release pressures a bit light maybe, or just not a very grippy synchro.  Might improve when the oil gets properly warm.

It's a real minefield.  New synchros aren't always great, decent used ones getting rare, and the cone surface on the gear can be a factor too.  You have to try the baulk rings on, see what gap is left (more the better in general), but also, push and twist them together.  A pair that is going to work well together will bite as you twist - it's difficult to describe - almost a squeak - but more a sensation of grip and friction than anything you can actually hear.  If they just slide, they won't work well.  I like to try a few and see.  I will choose one with good bite over another with less bite even if it has more gap.  Have seen new ones that are slightly out of round so have a great gap but minimal bite.

What gear oil are you using?  Can have a quite a big effect.  Redline MTL or MT90 works quite well for that I've found.

BTW on mine GT6 box I chose hub release pressures on the high side.  Synchro works well but it is a bit notchy so far.  Not as quiet as I would like either.

Nick

Good stuff, thanks. I'm using comma gl4 oil nothing fancy really. Some redline might be worth trying for sure. Hub release pressures I found difficult to measure but they all seemed about 9.5kg which is the upper range. How accurate my measurements were I'm not sure though! 

1 hour ago, Pete Lewis said:

3rd to 2nd is having to sync more revs than 1-2   and with a new clutch disc it may need the fuzz wearing in to clear nicely , i would give it some driving once the rota is fixed and see if it improves 

make  firm changes , if you hesitate through a change the rock over will let go and you crunch ... thats dont rush but dont release stick load during a change , if you know it might clash 

you can make it worse if you tickle it .

but a clearing clutch is fundamental to disc spin up synchronising 

pete

During changes I've been applying pressure to the stick to try and load the syncro slightly before slotting it in. I'll be a bit quicker and see how I get on. All good stuff to learn. 

I think the clutch is self adjusting (?) so as you say it will need to bed in. It's only done 2miles so far. 

43 minutes ago, Peter Truman said:

give the throttle a blip on the way down works for my Dolly on a worn box so should work on a rebuilt box, not a full double d'clutch but just a little blip, on the way up not to fast or slow but positive movement between  2 & 3, works for me no racing changes, eventually I'll pull the box and fix!

I can give this a go now I don't have a sticky throttle cable! What an annoyance that was, particularly around town. 

Link to comment
Share on other sites

  • 2 months later...

Bit of an update on things. With the car sporting new rotoflexs, rear cylinders and differential oil seals I took it out for a 20mile drive. All changes but 3rd-2nd are beautifully smooth. 

Blipping the throttle helps but without being down at 15-20mph road speed it will not select 2nd.

Is it the syncro next to second gear that is the culprit or the one next to third? Struggling to get my head around it. 

Link to comment
Share on other sites

Well assuming the gearlever linkage is all ok it'll be the second gear synchro ring thats not doing its job very well. This does changes up and down to 2nd but has to work harder on the down ones due to the bigger difference in rotation speeds which is why throttle blipping helps....

Link to comment
Share on other sites

51 minutes ago, johny said:

Well assuming the gearlever linkage is all ok it'll be the second gear synchro ring thats not doing its job very well. This does changes up and down to 2nd but has to work harder on the down ones due to the bigger difference in rotation speeds which is why throttle blipping helps....

My Vitesse is the same and only go from 3rd to 2nd at 20mph ish . Any more than that I get a “crunch” 

Paul 

Link to comment
Share on other sites

This synchro ring in particular has a hard life as drivers accelerate hard in first and whack into second. In any gearbox rebuild at the very least it should be swopped for the 4th or 1st gear ring which should be less worn.  Sometimes this maybe preferable to using a new pattern part item as their quality is pretty unknown and apparently can be distorted in manufacture so making smooth changes practically impossible....    

Link to comment
Share on other sites

1 minute ago, johny said:

This synchro ring in particular has a hard life as drivers accelerate hard in first and whack into second. In any gearbox rebuild at the very least it should be swopped for the 4th or 1st gear ring which should be less worn.  Sometimes this maybe preferable to using a new pattern part item as their quality is pretty unknown and apparently can be distorted in manufacture so making smooth changes practically impossible....    

Thanks for the reply. I do wonder as I replaced all the syncros with pattern items as they came in the rebuild kit from Paddocks. 

Just driven to work and the issue is much more acute in trafic, I had one smooth change but other than that it was a pain. 

Is there anything I can look at linkage wise? It's had a new set of bushes and the selector forks look in reasonable condition.

When I do get the box out I'll swap back to the old syncro rings on 2nd. Though they are all mixed up now so I'm not sure which is which. Having said that before the circlip issue from earlier all gears changed lovely so maybe any of them will be good. 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...