Mk3 GT6 Second Gear

[Ingieuk]

Hi All,

I'm wondering if you could advise me on an issue I have my rotoflex Mk3. On the way back from work today I have found that I was unable to go from 3rd to 2nd gear. Very occasionally in the past it has been reluctant but it always got there.

1st to 2nd, 2nd to 3rd, 3rd to 4th, 4th to 3rd, 2nd to 1st were all fine. It seems a curious fault. All was fine on the way this morning and the first half of the drive home. Going 3rd to 1st to 2nd worked to get home for the bits where 2nd was required but it is not ideal! No amount of trying to slip it in seemed to help and I was reticent to apply force!

When stationary it feels as though I can select any gear. 

The question I have is where to start looking? Is it likely to be in the mechanism or the box itself and am I likely to be facing a gearbox strip and rebuild? My experience with gearboxes is fairly limited, as it has not caused issue before

Thanks,

Rich

[johny]

Hi, I take the lever physically won't move into the second gear position from third? And yes don't force it!

[Ingieuk]

Hi, thanks for the reply.

No the lever will physically not move from third to second, pushing left and backwards just ends up with the lever over the left hand side.

I've just been out to have an extra run out and at lower engine speeds, when going from third to second if you push it slightly forward towards first, 50% of the time it will slot into second.

There were a couple of crunchy fourth to third changes too, it also felt like there was more drivetrain shuffle than normal in third. This could be me being very sensitive to anything unusual though.

I should say I've done around 3k miles/year in the GT6 since I got in 2013, so it gets a reasonable amount of use. I didn't do the original restoration though so I'm not sure on the history of the gearbox. 

[johny]

It sounds very much like your gear lever linkage is worn (very common) and the excessive play means the selector engagement lever on top of the box can't move to the right position. Luckily you can replace the various linkage bushes and bits external to the box but the gearbox cover/sound deadner will have to come off.

[Pete Lewis]

i agree start with a remote bush kit ,  eg http://www.jamespaddock.co.uk/gearchange-remote-bush-kit-4

available from canley rimmers and others 

as johny says needs the H frame and tunnel removing its all external to the main box , 4 nuts and its off the box ready for the kitchen table  !!

pete

[Ingieuk]

Thanks very much for the help.

As a parting shot after I'd bought the car the previous owner mentioned he had 'replaced the bushes in the gear stick' so I guess that means those bushes were done then. That is a few thousand miles ago though so I'll order one of those sets as a starter.

I should say it is a non-overdrive box (not that I guess that matters). 

I think it is unrelated but since I've had it the car has a tendency to kangaroo, particularly whilst under heavier load. It doesn't seem to happen when accelerating away from a roundabout, but on a steep sharp bend (of which there are a few round here - NY Moors) it can be quite bad. At first I thought maybe the clutch was slipping but the revs do not increase. As I say its probably unrelated but I thought I'd mention. If I do end up with the gearbox out I guess it is a good time to do the clutch whilst I'm in?

I'll make sure I introduce myself in the appropriate section.

Rich

 

[Pete Lewis]

the kit has a steel cup washer these are awful  and have a razor sharp cropped edge which will soon mince the plastic cup 

if you get a kit have a look and a run with a file will clean the ragged edges ,,  get some sticky plasters ready

when your ready ask how its fitted 

in fact if you start by remove the gaitor the minced cup may be obvious and the tunnel can stay in place 

Pete

[Ingieuk]

The bushings kit has now arrived. The cup is indeed razor sharp! I'll try getting the remote off later on and see where we get to. 

I need to work out how to remove the tunnel, the interior is nicely finished so I'll be taking it slow. 

Any tips on fitting the bushing kit? 

Thanks.

Richard 

[Pete Lewis]

yes some parts in the kit wont be needed

if you want to replace the main spherical the circlip is a swine to pick off, and note where the 2 springs go,

the 0 rings in the kit are to oil seal the remote shaft , they are hidden in the casting  dont go there 

getting on the bolt head can be tricky  but with the lever disconnected there is just enough rotation to get on it

refrain from undoing the square headed dowel bolt in the front selector , can be ridiculously   tight and doesnt need to come out 

then theres selection of plastic shouldered bushes and a ruberised one for the middle pivot

watch how  you  fit the bolt in the base pivot wrong  way  will foul the remote casting in 3rd/4th  

this all sounds worse in words than the job realy is .

Pete

[johny]

Remember to keep all the bits you don't use so you can start the essential collection of half used spares😂

[Ingieuk]

Interior is out. Transmission tunnel is out despite it's desire to stay stuck to the car by what looked like several tubes of mastic!

Gear remote is off, some interesting findings already. Hopefully I have managed to attach some pictures. There seems to be a quite a lot of wear on the female parts of the selector forks, particularly (maybe unsurprisingly) on 1st/2nd. There is also some wear on the right/left hand sides of the selector.

The remote itself seems fairly tight with little play. I'll replace the parts as discussed above (thanks Pete), but it does raise some other questions;

1) Are the selector forks worn enough to be causing the issue? (I imagine they are not helping)

2) Is the selector supposed to have flats on either side? (The flats almost look machined but could be wear)

3) There seems to be quite a lot of strain on the gearbox mounting rubbers - any idea of the typical places to check for this? None of the engine mounts look misaligned or in poor condition. It might be normal but if I took them off I'm not sure I'd be able to get them back on!

In the meantime I'll replace the bushes and try it out on the road (maybe in the week - can only leave a 1 year old with my wife for a few hours before I'm dragged back inside!)

Thanks again,

Richard

[johny]

Hi the mounts positioning looks ok to me but they are a bit perished. This isn't a problem as long as they are still well bonded to the metal ends. Sometimes replacement mounts don't last as long as serviceable originals...

With the gear selection you could try moving each selector locally with a suitable metal tool. Takes a bit of effort and of course 1/2 is in the middle, 3/4 left side and reverse right.

[Pete Lewis]

the offset and distortion on the mounts is pretty normal

the wear on the  sides of the selector is not going to give any problems 

if you grip the inward selector there should be no play in the bushes / rods or up to the gearstick 

is the reverse stop set correctly , this stop controls the alignment to 1/2nd  and does the stick spring up/down to clear the reverse stop. if the stick is stiff or sticking down then  you left right has no position for 1st/2nd ???

and we have not mentioned the clutch  all synchronized changes rely on the clutch clearing , any disc drag will baulk a change 

Pete

[NonMember]

Thinking about the specific problem you reported, with 3rd-to-2nd changes, two things strike me.

1) The wear you noted on the selector forks, particularly the 1st/2nd one. There's a distinct dimple here:

That's just where the selector pin is likely to hit on a fast 3->2 change and might hold it out of line enough to catch the 3/4 selector on the left, with the result that it tries to select both 2nd and 4th. There's an interlock detent ball specifically to prevent that, which brings me to...

2) if the spring behind the detent ball has failed, it could also make it hard to select 1st or 2nd after leaving 3rd or 4th.

[Ingieuk]

8 hours ago, johny said:

Hi the mounts positioning looks ok to me but they are a bit perished. This isn't a problem as long as they are still well bonded to the metal ends. Sometimes replacement mounts don't last as long as serviceable originals...

With the gear selection you could try moving each selector locally with a suitable metal tool. Takes a bit of effort and of course 1/2 is in the middle, 3/4 left side and reverse right.

Thanks, they are well bonded so I'll leave them be. As you can see below I've struggled with the repro bushes for the gear remote for a similar reason.

 

8 hours ago, Pete Lewis said:

if you grip the inward selector there should be no play in the bushes / rods or up to the gearstick 

is the reverse stop set correctly , this stop controls the alignment to 1/2nd  and does the stick spring up/down to clear the reverse stop. if the stick is stiff or sticking down then  you left right has no position for 1st/2nd ???

and we have not mentioned the clutch  all synchronized changes rely on the clutch clearing , any disc drag will baulk a change 

There is some slight play in the first pivot and the fork - though the bolting was quite loose. Neither seem particularly worn compared to the replacement kit, however the kit is not of the quality I would expect. The black buses are very mis-shapen, the pivot ball is far from smooth and smaller cup washer I have removed is fairly sturdy and metal - whereas the replacement is a beige plastic with big mould marks. I'm going to get in touch with Canley Classics as the black bushes in particular are basically unuseable. The other parts are useable with a bit of filing but that rather defeats the point of buying a bush kit to take up play in a linkage! I've attached a photo of the two misshapen bushes and the old and new pivot

The reverse stop seems set okay - never had any issues getting it in, goes in nice and positive. No issues with it sticking in either, everything is nicely greased and free.

The clutch was something that did cross my mind. I noted when I serviced it last the fluid was rather black. In the 7 years I've owned the car I've done nothing to the clutch, cylinders or fluid. I have had some judder over the last year or so that can occasionally get quite bad. Also there is the slight kangarooing at low rpm/higher load. Any areas I can check? The slave cylinder looked in good nick when I had a cursory glance today.

6 hours ago, NonMember said:

Thinking about the specific problem you reported, with 3rd-to-2nd changes, two things strike me.

1) The wear you noted on the selector forks, particularly the 1st/2nd one. There's a distinct dimple here:

That's just where the selector pin is likely to hit on a fast 3->2 change and might hold it out of line enough to catch the 3/4 selector on the left, with the result that it tries to select both 2nd and 4th. There's an interlock detent ball specifically to prevent that, which brings me to...

2) if the spring behind the detent ball has failed, it could also make it hard to select 1st or 2nd after leaving 3rd or 4th.

Good thinking! Though running my finger over the area it may be a trick of the light as it feels like it is more worn towards the centre, though the transition between the 1/2 and 3/4 selectors is worn.

From the workshop manual the interlock you mention seems to be two ball bearings with a shuttle piece between them, presumably they engage internally in each of the selectors so that only one will slide at a time. The exploded diagram also has a detent pin and spring for each of the selector shafts. I'm not clear on what these detent pins engage in or do though?

I've tried to take a photo of the exploded diagram. The interlock ball bearings are item 110, the shuttle piece 111, the three detent pins 85 and the detent springs 86.

The workshop manual doesn't state it outright but it alludes to being able to remove the selector shafts along with the top casting of the gearbox without removing it from the car. Though as Pete points out regarding the clutch, it might be best for me to just bite the bullet and get the gearbox out of the car and take a look at the lot whilst its out. At least the weather is good and I can work until 9:30pm before having to push the car back in the garage!

 

Thanks all for the help you have provided, it really is invaluable. I hope adding photos and (fingers crossed) a solution at the end will be a decent reference for others with the same issue!

Richard

[johny]

As I say can you try to move those selectors by hand to test their operation and check the detects? Get an appropriate tool (something similar to the ball of the operating arm?) in each slot and slide each through their normal travel. There's a bit of resistance and then they should suddenly slide into gear so careful of fingers and knuckles. Don't force anything...

The whole selector assembly will indeed unbolt from the top of the cast iron gearbox case and can be lifted off to leave just the gear shafts below.

[Ingieuk]

45 minutes ago, johny said:

As I say can you try to move those selectors by hand to test their operation and check the detects? Get an appropriate tool (something similar to the ball of the operating arm?) in each slot and slide each through their normal travel. There's a bit of resistance and then they should suddenly slide into gear so careful of fingers and knuckles. Don't force anything...

The whole selector assembly will indeed unbolt from the top of the cast iron gearbox case and can be lifted off to leave just the gear shafts below.

I'll have a go at that tonight. I've got some 6mm mild steel rod I can round the edges off to use as a tool. Ill keep my fingers out the way! 

If the gears select okay I'll take the top section off to have a look at the wear on the forks and check the interlock balls/detents.

 

[johny]

Well if the gears all select ok the theory is that the problem is elsewhere with the lever mechanism as the prime suspect. I wouldn't disturb more than necessary and of course don't drop anything in the open box!

[Pete Lewis]

 on a different track  when you were driving did the gear lever tend to move back and forth as you accelerate decelerate

you can only examine the detents and the interlock balls and pin by a full disassembly of the top cover shafts and forks 

i suggest you leave that  idea  alone for now 

Pete

 

[Ingieuk]

50 minutes ago, Pete Lewis said:

 on a different track  when you were driving did the gear lever tend to move back and forth as you accelerate decelerate

you can only examine the detents and the interlock balls and pin by a full disassembly of the top cover shafts and forks 

i suggest you leave that  idea  alone for now 

Pete

 

Yes it did, every time. Though it has done this for quite a while. What might this suggest?

I'll curb my disassembly enthusiasm and get the remote sorted tonight. 

Thanks again, 

Richard 

[Pete Lewis]

i now have a feeling the circlip behind the rear main ball race has popped off , this allows the whole internals to shift from the helical loads and it transmits to stick shake 

as youre not overdrive its  discon the prop remove g box coupling,   lift the tail of box up,   and remove the tail extension hsg, the circlip will be visible without having to remove the gearbox   (note all the oil will escape )

Pete

[Ingieuk]

11 hours ago, johny said:

As I say can you try to move those selectors by hand to test their operation and check the detects? Get an appropriate tool (something similar to the ball of the operating arm?) in each slot and slide each through their normal travel. There's a bit of resistance and then they should suddenly slide into gear so careful of fingers and knuckles. Don't force anything...

The whole selector assembly will indeed unbolt from the top of the cast iron gearbox case and can be lifted off to leave just the gear shafts below.

Tried this out, can select all gears reasonably easily. There is some more resistance when moving from the 1st/2nd selector to the 3rd/4th one. 

I did also try to select two gears at once (gently obviously) and it feels like the interlock mechanism was working, the other selector coming up snug against something hard. Got some better pictures of the wear I'll share when boot my laptop up later. 

5 hours ago, Pete Lewis said:

i now have a feeling the circlip behind the rear main ball race has popped off , this allows the whole internals to shift from the helical loads and it transmits to stick shake 

as youre not overdrive its  discon the prop remove g box coupling,   lift the tail of box up,   and remove the tail extension hsg, the circlip will be visible without having to remove the gearbox   (note all the oil will escape )

Pete

That's a interesting thought, I'll try and see where it is on the exploded diagram so I get in my head what I'm looking for. 

So disconnect the prop shaft - might need to put it on stands as won't be able to turn the shaft to access all the bolts? 

Is the circlip at the oil seal end of the extension or the box end? Sorry not sure what an 'hsg' is either! 

[Pete Lewis]

sorry hsg   abbreviated  housing   the alloy tail housing  the circlip fits up against the cast cast rear ball race , opposite end to the coupling

up by the gasket on here  https://www.canleyclassics.com/?catalogue=triumph-gt6-mkiii&diagram=triumph-gt6-mkiii-casing-speedo-driven-gear

the circlip 500872   https://www.canleyclassics.com/?catalogue=triumph-gt6-mkiii&diagram=triumph-gt6-mkiii-mainshaft-and-gears

 

the fork press load on 1/2nd will be higher than 3/4th thats correct 

yes needs a wheel up to rotate the prop , all bolts are above the chassis 

Pete

[johny]

Well now if the gear lever assembly has been overhauled (when holding the selector operator stationary you shouldnt be able to waggle the gear lever from side to side at all) you could try putting it back in place to try gear selection...

[Ingieuk]

13 minutes ago, Pete Lewis said:

sorry hsg   abbreviated  housing   the alloy tail housing  the circlip fits up against the cast cast rear ball race , opposite end to the coupling

up by the gasket on here  https://www.canleyclassics.com/?catalogue=triumph-gt6-mkiii&diagram=triumph-gt6-mkiii-casing-speedo-driven-gear

the circlip 500872   https://www.canleyclassics.com/?catalogue=triumph-gt6-mkiii&diagram=triumph-gt6-mkiii-mainshaft-and-gears

 

the fork press load on 1/2nd will be higher than 3/4th thats correct 

yes needs a wheel up to rotate the prop , all bolts are above the chassis 

Pete

Thanks that is clear now. I guess it is not normal for the gear lever to shift under loading/unloading of the transmission? 

 

9 minutes ago, johny said:

Well now if the gear lever assembly has been overhauled (when holding the selector operator stationary you shouldnt be able to waggle the gear lever from side to side at all) you could try putting it back in place to try gear selection...

I'll see where I get to tonight. I was able to select all gears when stationary, but when on the move and under load I could not select 2nd from 3rd. I could declutch a couple of times and just about slide it into 1st. Once in 1st I could go back up the box again.