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Mk3 GT6 Second Gear


Ingieuk

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there will always be a hint of movement  but if the stick does a deliberate back and forwards on drive/overrun then something thats supposed to be fixed has got some endfloat it should not have 

have to say circlip popped is not quite common but it happens   there is also one at 3rd gear , but as you have  a 2nd  selection its my view 

the mainshaft is floating its this silly small circlip takes control of all the thrust, 

Pete

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1 hour ago, Pete Lewis said:

there will always be a hint of movement  but if the stick does a deliberate back and forwards on drive/overrun then something thats supposed to be fixed has got some endfloat it should not have 

have to say circlip popped is not quite common but it happens   there is also one at 3rd gear , but as you have  a 2nd  selection its my view 

the mainshaft is floating its this silly small circlip takes control of all the thrust, 

Pete

Thanks Pete, it's quite pronounced, the gear stick moving 1/2in or so. Don't imagine that is the end float in the box but by the time it's transmitted the movement up the linkage it's obvious. 

 

I've got the remote rebuilt using a hybrid of old and new parts. I didn't remove the circlip in the end as the pivot bush was in good condition with little play. New nylon washers on the pivot closest to the selector took up quite a lot of slack. The reverse spring that comes with the kit is a bit weaker than the original so I may change that back at some point. I've also set the reverse stop bolt again, though it was only 0.15mm off the workshop manual 1.25mm gap. 

No slack at all in the linkage and the remote is back on the car, definitely feels nicer. All gears select positively with an audible click, particularly with the tunnel off. 

Before I go checking the circlip Pete mentions I'm going to go for a ten min run out tomorrow evening to see if the work so far has helped find the 3rd to 2nd change. Only want to change one thing at a time. 

I've got some more pictures of the selector forks I'll add for reference in a post below. 

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i wouldnt worry too much about the wear marks on the wards of the forks they have been well used but wont stop you engaging any gears

to further access if the gears have too much end float you could take the top cover off,  think on a 4 synchro you need to engage 1st gear to be able to lift off and refit the top cover and re align the reverse lever to refit .

if you pry 2nd gear(lever with decent screwdriver )  and there is more than a few thou movement up down the mainshaft ....its you circlip is adrift 

you may find as you lever the coupling moves.. it must not 

have a look at the coupling oil seal has it got a new running position or signs of shift ???

Pete

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Just had another thought about the possibility of the reverse stop bolt being longer than standard. If it has been changed st some stage and is too long could that make 1/2 gear change difficult even if set correctly? Wonder if operator position could be measured with lever against reverse stop and compared with 1/2 selector slot...

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11 hours ago, johny said:

Just had another thought about the possibility of the reverse stop bolt being longer than standard. If it has been changed st some stage and is too long could that make 1/2 gear change difficult even if set correctly? Wonder if operator position could be measured with lever against reverse stop and compared with 1/2 selector slot...

 

8 hours ago, Pete Lewis said:

i would sub assy the remote to the box and set the stop bolt to give the 000.to 0.050" between stop bolt and plate when held to the left side of the H gate

Pete

I'll have a look at the reverse stop plate before I remove the remote again.

 

I've just been for a quick run out and it is unfortunately no better. Moving away from a junction and up the box is no issue, everything selecting really nicely (the bushings have improved that). Coming down it will not select 2nd at all. Just about get 1st and then into second no issues. If in 3rd gear you put the clutch in, roll to a stop you can then select 2nd. So the issue is somehow related to gearbox shaft speed (or position - circlip?)

Next thing to try is removing the gearbox oil and removing the rear extension to check the circlip - though may only get as far as the oil tonight.

I've ordered a new clutch friction disc, pressure plate, release bearing, master and slave overhaul kits. I concluded that having gone this far I might as well do the clutch to see if it sorts the judder out. Plus the master/slave cylinders are of unknown age and condition (though fluid is black!).

 

12 hours ago, Pete Lewis said:

i wouldnt worry too much about the wear marks on the wards of the forks they have been well used but wont stop you engaging any gears

to further access if the gears have too much end float you could take the top cover off,  think on a 4 synchro you need to engage 1st gear to be able to lift off and refit the top cover and re align the reverse lever to refit .

if you pry 2nd gear(lever with decent screwdriver )  and there is more than a few thou movement up down the mainshaft ....its you circlip is adrift 

you may find as you lever the coupling moves.. it must not 

have a look at the coupling oil seal has it got a new running position or signs of shift ???

Pete

One question Pete if you do not mind - I'm a little stuck on the coupling you mention - is this the mainshaft to propshaft drive flange (where the rear oil seal is) or the input shaft to mainshaft coupling? I understand the circlip in question is at the rear of the mainshaft but I'm unsure where I'm looking for the coupling. Maybe it will all come clear once I get going.

 

Thanks,

Richard

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yes  a coupling is the drive flange 

if you get to having to look see ,   then once the prop is dropped down the coupling nut is quite tight 70-80 lbft   and you  need to lock it from turning  simplest is  two old bolts in the coupling holes and a lever jammed between them to arrest rotation 

the coupling should pull off by hand  or may need a bit of a tap .

Pete

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Just dropped the gearbox oil out to have a look at the rear extension and found what appears to be a piece of circlip and the edge of two teeth. This doesn't fill me with confidence! Anyone recognise the circlip? Looks like it might be a bearing retainer, or maybe one of the clips off the mainshaft? 

DSC_0202.JPG

DSC_0204.JPG

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Hmmmm.... teeth are probably from one of the reverse gears. Not necessarily a show stopper. If reverse works now without odd noises and without jumping out, it’ll be fine.

Circlip looks like the one under third gear.

Looking inside 6 cylinder gearboxes tends to lead to disappointment in my experience..... always busted..... only the degree of busted varies.

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26 minutes ago, Pete Lewis said:

looks more like the one off  the   3rd gear end thats a square section the tail brg, end is a flat one 

if failed has same selection  effect

its looking like box   off 

where are you located ?

pete

Yes I think the box is coming out now. Looks like the front oil seal in the bellhousing is leaking too after getting under car. 

I'm up in the North East near Stokesley. 

22 minutes ago, Nick Jones said:

Hmmmm.... teeth are probably from one of the reverse gears. Not necessarily a show stopper. If reverse works now without odd noises and without jumping out, it’ll be fine.

Circlip looks like the one under third gear.

Looking inside 6 cylinder gearboxes tends to lead to disappointment in my experience..... always busted..... only the degree of busted varies.

Fingers crossed its the reverse gear then! Didn't realise the 6cylinder gearbox was a weak point! Is it the same box for the 1500 spit just with an extra 2 cylinders and 0.5l?

 

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Wow okay, it is at its limit then! 

As it happens when I last changed the gbox oil in 2016 I found a very small piece of circlip, 1mm long. I happened to keep it, and comparing thickness it's identical to the larger piece found today (1.78mm). So maybe this has been on its way for a while! 

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Yes unfortunately it's likely that you'll find some other worn components in the box and will have to decide whether to live with them or spend some money. Either way there's plenty of expertise on here to help you decide....

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have a look at the Standard eight !!!!!!   but in the trade most things like a gearbox have all evolved from early designs  whatever marque .

thats a bit far??? to suggest a trip with the box to sunny Luton ????

you do the work i act a s foreman    

Pete

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reff,n t,what Pete said about the rear bearing,

id,never seen a  rear  alloy housing worn away till i took a box apart a while ago

 

basicly the bearing had spun int gb housing, this then wore the alloy housing away

 

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i remember just after short trousers doing a Viva Gearbox ( you think ours are weedy ) and the rear bearing and tail housing are locked on with  giant circlip

well this one had minced the  alloy  tail and  the groove for the clip to shreads by the time i got the mess off it was a bit terminal , someone pinched a tail from the factory and it got rebuilt 

it had been run with no oil and the rear bearing had seized turning in the box .

Pete

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On 04/06/2020 at 07:44, Pete Lewis said:

have a look at the Standard eight !!!!!!   but in the trade most things like a gearbox have all evolved from early designs  whatever marque .

thats a bit far??? to suggest a trip with the box to sunny Luton ????

you do the work i act a s foreman    

Pete

Luton might be a bit far! Nevermind let's do it in a socially distant manner on here :)

 

Thanks all for the help and anecdotes, all very interesting! 

I spent most of last night getting the box ready to come out. Starter motor off, propshaft flange joint loose, rubber mounts loose and all but two bell housing bolts removed. 

Just need to remove the slave clutch cylinder tonight and will get the box out tomorrow (with socially distant help!). 

I've ordered a rebuild kit from James Paddock which includes bearings, needle rollers, syncro rings, layshaft thrust washers, new layshaft, new oil seals, gaskets and circlips. Anything else I should be looking at while I'm in? 

Master/slave cylinders will get an overhaul, new clutch to go in, new rubber gearbox mounts. Lots to be getting on with over the next few weeks. 

Rich

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You'll need to look at the condition of the surfaces where needle rollers run on directly. These are the tip of the main shaft and corresponding hole in the input shaft plus inside each end of the laygear. These areas are surface hardened and once this is worn through are a problem....

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you may need the springs 3  for 1/2 hub and 3/4th hub sleeves  ( each hub has different springs )

and a plastic bag to use fitting new balls and springs so when the sleeve moves and the balls ans spring escape you catch them in the back  

this tip is worth a strong tea 

and wire the sleeves on the hubs   de wire when refitting , 

there are some simple tips on rebuilds ...ask when youre ready as the two 2nd gear collet thrusts can be a nightmare without some help

Pete

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Thanks Johny/Pete, I'll see when I get up to that bit. 

 

Got the master/slave clutch cylinders off now. The state of the fluid is a little embarrassing. It's like mud. Quite how the clutch was operating I don't know. Any tips on what dissolves old gummed brakefluid? Brake cleaner didn't seem to touch it. I need to loosen it off to get the plunger out (air lance to the clutch line should shift it once loose).

 

DSC_0209.JPG

DSC_0208.JPG

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18 hours ago, Pete Lewis said:

you may need the springs 3  for 1/2 hub and 3/4th hub sleeves  ( each hub has different springs )

and a plastic bag to use fitting new balls and springs so when the sleeve moves and the balls ans spring escape you catch them in the back  

this tip is worth a strong tea 

and wire the sleeves on the hubs   de wire when refitting , 

there are some simple tips on rebuilds ...ask when youre ready as the two 2nd gear collet thrusts can be a nightmare without some help

Pete

48 posts till the first mention of tea, whats going on!
Come on guys this is a serious bit of work Rich is undertaking and will require more than a few cups.
This one will also require cake.

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