Gearbox problems

Drivetrain problems

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Re: Gearbox problems

Postby bobbrown » Thu 09.04.2009, 17:21

I spoke to Gerald at GST today, car was in getting the oil leak fixed, and I asked him about this specific issue and I now understand what is going on.

When the nut/nuts come loose if it/they back off too much it allows the shaft to move and that allows shims to drop down a step in the shaft, not sure if it main shaft or lay shaft forgot to ask that.
If this happens when you re-tighten the nut it causes the gear train to jam as the gears are not in the correct position.

His fix is to slacken the nut and briefly run the engine which spins the gearbox and with a bit of luck the shims end up in the correct position then tighten the nut again.
Bit fiddly but it save taking the box out, also he mentioned the fact these nuts are of the stake variety and should be changed as you need to re stake them much the same as the front hub nuts.
On top of that if it has been loose for some time then the syncro on 5 th can move and need to be pressed back into the correct position. If this is the case the box will jam or be very difficult to change gear as the selector for 5 th is not in the correct position.

So to summarise when the nut/nuts come loose is not necessarily as straight forward as one would think but it is all possible with out the need to remove or replace the gear box.

Bob
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Re: Gearbox problems

Postby RayD » Thu 09.04.2009, 21:51

Since Rip mentioned the shims dropping I've been going boss eyed trying to see where they’re dropping to.

There’s a shim on each of the 3 shafts including the diff.

If the shims can fall, try to imagine how rotating the shafts would get them back in position. :?

I was beginning to think it was gears that were causing it not to slide back into place. Knowing now, rotatating the shafts solves it, I'm even more inclined.

Ray
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Re: Gearbox problems

Postby bobbrown » Thu 09.04.2009, 23:25

Ray,

I was only repeating what Gerald said, I too could not see any shims as such but it seemed to imply that rotating the shafts seem to put some thing back in place.
I must have worked for him in the past because he said if it was not right after tightening the nuts to slacken them off again and rotate every thing and the nuts would tighten further than before.
I could sort of understand it, if a shim had drop off a step in the shaft and you turned the shaft 180 degrees it would drop again but at some point it may line up again enabling it to re-seat.
In this case I do not quite see what is likely to drop but as the diagrams are not that clear it is difficult to say. The shims you mention just preload the main shaft, lay shaft and diff tapered roller bearings and as I see it hold all the gears together apart from 5 th which is just stuck on the end. It may be it is not a shim but something else that has not seated properly and the rotation allows it to go back into position. What ever it is it seems to work as he did one recently.
No doubt if you took it to a main dealer they would have the box out and in pieces or fit a new one at vast expence.

I have worked on gear boxes in the past and a typical LT77 box failure was the lay shaft bearings to fail and you were left with only one gear, 4 th as it was direct drive, but if it works it works.

Bob
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Re: Gearbox problems

Postby Specky » Fri 10.04.2009, 11:59

I'll undertake this task on monday and let you know what happens and things go...

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Re: Gearbox problems

Postby RayD » Fri 10.04.2009, 17:17

I agree with you Bob,

The main thing is... now we know... whatever is holding it out of place can be solved by turning the shafts.

Reading the manual there seems to be only the three shims for the bearings.

From Dave’s point of view - trying it on Monday - it would be handy if we could find out if you can tell, just by looking, with the position of the nut or something else whether it’s stood off or not.

The shims are only 1 to 2½ mm thick so if it’s one of those causing it, it might not be noticeable to the eye.

If it’s something else (the ring behind the fifth gear holding the inner race in for instance) and it’s being held off say 4-6mm you may be able to tell.

When it’s in the wrong position there might also be excessive lift in the shaft, with the nut loose.

If someone tries it with the engine out of action, or they wanted to be extra careful, it might be a good idea to have someone turn the engine back and forth by hand while the nut is being run up.

It’s interesting the manual makes a point of mentioning the shafts ought to be vertical when being built up as though there’s one of the parts relying on it to stay in place.

Ray
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Re: Gearbox problems

Postby RayD » Fri 10.04.2009, 17:26

......
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Re: Gearbox problems

Postby valimar » Fri 10.04.2009, 17:54

We can always find out the initial place where the nuts have been fastened. The shafts have 2 places where you have to stake the nuts. If you fasten the nuts till they reach (more or less) the right torque and are aligned with the 2 notches of the shafts, then you have the initial position.
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Re: Gearbox problems

Postby Specky » Fri 10.04.2009, 18:04

Ray,

I've got a few other gearboxs laid around so I'll compare them as well

I'll take some photo's...and a bit of servicing by comparrision

I think one of the most obvious things will be the number of screw threads visible at the end of the shaft.... and the locking will have failed....(Feeler Guages on stand by)

I'm glad we've nearly got to the bottom of it... I do know Candles did this years ago , and he said..."basically it just tighten it back up"...




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Re: Gearbox problems

Postby RayD » Fri 10.04.2009, 19:03

Specky wrote:
I do know Candles did this years ago , and he said..."basically it just tighten it back up"...



Most of the time it might be as simple as that Dave.



valimar wrote:
If you fasten the nuts till they reach (more or less) the right torque and are aligned with the 2 notches of the shafts, then you have the initial position.



Good point Rodrigo, It's just a matter of finding out how far out it is when it's wrong. Hopefully it's not a tiny amount - one full turn.

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Re: Gearbox problems

Postby Specky » Tue 14.04.2009, 22:31

Here's how I sorted my gearbox which was jammed 5th gear...

As gearbox issues go, this is quite rare

If you're reading this after a brief search and think it sounds familiar but not quite right, please check the following:-

Gear cables, they can break/split on the black plastic adjusting knobs, these are situated on the rear of the gear box.

There is a mount is secured to the back of the gearbox, the gear cables are secured using either wire "C" retainers or flat metal "E" retainers (95% probability this is the cause)

Check the Gearbox selector

or your Gearbox shaft nuts may be lose



Car ready...Check.....

spare Gearbox ready....check

GB1.jpg


Jack the car, remove the road wheel

GB2.jpg


Remove the end cover...

GB3.jpg


I've moved to the spare gearbox, just for the ease of photographs and just in case I require some bits

GB4.jpg


I removed the 3 detent bolts (springs etc) incluing reverse switch

Then removed the two role pins which hold on the 5th gear selector fork (the small Role pin sits inside the large Role pin)

GB5.jpg


Warning !!! make sure there is clearance for the pins, if the cars in 5th you may struggle

GB9.jpg


Next put the car in 3rd or 4th

Then manually push the 5th gear selector fork inboard...This engages 5th as well as the earlier selected 3rd or 4th...The gearbox is now locked

GB6.jpg


This is what it looks like on the car

Torque check the two nuts 127Nm IIRC

Rectify any issues IAW the manual

GB7.jpg


I removed the selector due to the fact it had excessive play. I also wanted to check it for wear and carry out a tolerence check in accordance with the manual.

When you remove the selector three bits will fall out, don't worry they go back in...

GB8.jpg


and if you've this far, start putting her back together again

and hopefully your 5th gear issue has gone



TTFN
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Re: Gearbox problems

Postby RayD » Wed 15.04.2009, 19:19

Great job Dave, no doubt others will benefit in future.

Had the locking marks on the nuts moved from the grooves?

Or were the nuts still in their original place with everything moving away from them due to wear?

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Re: Gearbox problems

Postby Specky » Wed 15.04.2009, 22:25

RayD wrote:Great job Dave, no doubt others will benefit in future.

Had the locking marks on the nuts moved from the grooves?

Or were the nuts still in their original place with everything moving away from them due to wear?

Ray


The peining marks on both gear boxees were terrible, one gearbox looked none existant... saying that all four nuts had begun to come out of there locking and I guess like everything the torque had begun to drop off...

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Re: Gearbox problems

Postby valimar » Thu 16.04.2009, 16:26

Nice pics Specky, we all appreciate it! Now I have a little problem and maybe if you have a gear selector around, you can help me: I was mounting the selector when i notice that the actuating finger was placed back-to-front refering to the drawing of the lotus service notes (section FF, page 34) I took it out and put it like appears on the drawing, but i wonder if this is the correct way or the drawing could be wrong! As an attachment i send a pic of the selector as it looks now!Do any of you know what is the right way? Please let me know!
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Re: Gearbox problems

Postby bobbrown » Thu 16.04.2009, 17:27

this may help
AB motosport short shift
abmotosport.jpg
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Re: Gearbox problems

Postby Specky » Thu 16.04.2009, 18:11

Bob Has answered your question,

So thats a big yes and you have a second geration selector as well

Only use these for comparrision as one is U/S

TTFN
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Last edited by Specky on Thu 16.04.2009, 18:28, edited 1 time in total.
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Re: Gearbox problems

Postby valimar » Thu 16.04.2009, 18:25

Thanks Guys! Then it means that the drawing in the Lotus service notes is very wrong!
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Re: Gearbox problems

Postby RayD » Thu 16.04.2009, 21:01

...
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Re: Gearbox problems

Postby valimar » Fri 17.04.2009, 08:40

Ray, as you well marked in red, the actuating finger is definitely wrong placed on the drawing! Useful for all of us when assembling the selector after consulting the service notes...
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Re: Gearbox problems

Postby ektrolleyboy » Mon 27.04.2009, 08:18

I attacked the gearbox problems thread... Sorry!

My second gear has just started to be graunchy when cold. Only for the first few changes or so... It wasn't there before! Third's a bugger on fast changes too, but they all are I think. More concerned with second. It drives fine when warmed-up.
Is this a sign of something to come? I've just had the major A and C (or whatever is it is) service with Paul Matty. Would they have changed the gearbox oil?
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Re: Gearbox problems

Postby rip » Mon 27.04.2009, 11:09

ektrolleyboy wrote:Is this a sign of something to come?

Possibly synchro hubs starting to break up. My 3rd was a bit crunchy but an oil change has helped enormously.
ektrolleyboy wrote: I've just had the major A and C (or whatever is it is) service with Paul Matty. Would they have changed the gearbox oil?

Service schedules & what gets done at each are all in the wiki. Gearbox oil gets renewed at a C service. I doubt Paul Matty would have cheated this.
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