Lotus Elan

gearbox clip.

PostPost by: davidj » Mon Feb 20, 2017 8:16 pm

Good evening,

When I took my gearbox apart, there was a spring clip on the 3rd/4th selector rod, as shown in the picture. Is it required? it is not shown in the manual, and it does not look to serve any purpose. I still have it, so can fit if required. However, potentially could drop off in the future and fall into the mechanism.

Thanks again in advance for any suggestions/advice.

David
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PostPost by: Craven » Mon Feb 20, 2017 11:06 pm

Hi David,
There is a small range of lengths for the loose sleeve, and for the clip thickness you describe (usually colour coded).
Selected on assembly to limit the overthrow/movement of the outer part of the sychro hub (3rd gear).
So yes its needed, refit, unless major parts have been replaced in which case a new sleeve clip combination will have to be determined.
Ron.
Ps, more to these gearboxes than some think.
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PostPost by: promotor » Tue Feb 21, 2017 8:08 am

Later gearboxes used a longer tube on 3rd/4th so that the clip wasn't used - possibly to save Ford costs, but most likely to save against claims from stray clips damaging the gearbox.

I always fit a tube without the clip as they concern me!

As mentioned it is to stop "overstroking" of the synchroniser assembly which crashes into 3rd gear without it. 4th gear doesn't overstroke as the bellhousing stops the selector rod going any further than necessary.
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PostPost by: davidj » Tue Feb 21, 2017 12:46 pm

Interesting. That did not occur to me, and you are correct about being colour coded, the clip is red. I have fitted a new selector fork for 3rd/4th, as the original was very badly worn, which is a significant change. Is there a simple method to determine if it is still required? Obviously, it goes into gear with or without the clip. With the clip is fitted, there is very little forward/backwards play in the sleeve, which I guess is preferred?


Yes, there is more to these gearboxes than is documented!

Cheers,

David
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PostPost by: promotor » Tue Feb 21, 2017 1:44 pm

davidj wrote: Is there a simple method to determine if it is still required?


Yes select 3rd gear while pressing the detent ball down (with a fair amount of pressure) into the detent on the 3rd/4th selector rail - you don't want the fork moving any further than the detent ball allows the rail/fork to travel.
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PostPost by: davidj » Thu Feb 23, 2017 12:44 pm

Hello again,

I don't know if I am missing something, but in my gearbox at least, I cannot see how there could be sufficient overstroke for the synchroniser assembly to hit the 3rd gear, with or without the clip.

When third gear is selected, the syncro moves back to engage in the syncro teeth of the third gear, and the selector fork pushes the sleeve back to hit the rear of the gearbox. At this point, the syncro cannot move any further back, and is still 3-4 mm clear of the third gear, a bit more if the clip is fitted, but in this case the syncro does not appear to fully engage in the teeth.

Sorry if I am being rather stupid about this but it does not appear to make any difference whether the clip is fitted or not??????? :?

Cheers,

David
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PostPost by: promotor » Thu Feb 23, 2017 2:32 pm

Definitely not stupid - just getting around the vagaries of the 3 rail box!

How thick is the clip? It should be approx 2-3mm.

It's possible that you have the longer tube already installed so that the gearbox doesn't need the clip - how long is the tube?

Does the synchro sleeve not slide over 3rd gear dogs when using the clip/without the clip/or both? There could be other issues at hand if the synchro sleeve is nowhere near to covering the 3rd gear dogs and you have actually got the correct length tube in :

If your 3rd/4th gear selector fork contact pads are worn substantially that will stop you overstroking as you'll have less travel available as you'll be taking up too much slack before actually moving the synchro sleeve. Selector forks are approx 0.236" thick from new. Most will wear on 4th gear side, some wear on 3rd side and a few will wear on both - depends on whether the synchros have been struggling to slow down/speed up the gears so the gear selection is "forced", and/or whether a driver rests their hand on the gearlever when not changing gear as this will likely load/push the selector fork into the synchro sleeve and if done over a long period of time will wear the fork.
You need to be checking the position of the synchro sleeve and its engagement with 3rd (and 4th to be sure everything is OK) with the ball(s) in the detents as that dictates the correct position that all 'boxes are based around.

Ultimately if the sleeve has passed the gear dogs substantially and the detent ball is in the bottom of the detent then all is well. The tube is the final tuning to stop any clash or potential tipping of the blocker bars.
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PostPost by: Craven » Thu Feb 23, 2017 2:57 pm

Hi David,
If the old selector fork was badly worn then engagement of 3rd gear must have been marginal at best.
Bit of a pain but you need to refit old fork and compare position, failing that double check the new fork dimensions.
From this pic hopefully you can see the synchro ring needs to pass quite a long way over the gear before the dog teeth are fully engaged.
Ron.
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PostPost by: davidj » Fri Feb 24, 2017 1:11 pm

Wow, thanks again for your replies.

Yes, the 3rd/4th selector fork was badly worn which is why I replaced it. It was worn on both sides but as suggested, more so on the 4th gear side. It was well past it's best.

The sleeve is 84mm, while the clip is 67 thou. (metric ruler, imperial mic!).Is this the longer tube version? In the pictures you can just see the effects of fitting the clup. In 3rd, without the clip fitted and with the new fork, the synchro sleeve just clears the gear dogs, while with it, the dogs are just proud. Consequently, I think it will be wise to leave it out. In the pictures you can also see the clearance to 3rd gear.

Cheers!
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PostPost by: Craven » Fri Feb 24, 2017 4:29 pm

Hi David,
Only ones to hand :- RED Sleeve = 82.7mm Plain Sleeve = 84mm
Red Clip = 2.5mm White Clip = 2.23mm
If you can deduce anything from this it would be you don?t need the clip?
Just leaves the question in my mind WHY was a clip fitted, personally don?t like unanswered questions.
Ron.
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PostPost by: davidj » Fri Feb 24, 2017 6:52 pm

Hello again.

As my sleeve is 84mm long, have I the longer version? This could explain why the syncro appears to operate correctly without the clip.

I don?t like unanswered questions either and I may have a possible answer; the gearbox has been very badly rebuilt in the past. I discovered damaged speedo worm gear, incorrect syncro rings, original seals; incorrect bearings. the list goes on and on. I originally took it out of the car because I could not select reverse and discovered the remains of a sleeve jamming the reverse gear.

So one possible scenario is that the plonker who rebuilt the gearbox lost the original, shorter sleeve, inside the box, and obtained another, longer one. He fitted the clip as well not realizing it was no longer required!

It does not explain why my red clip is 1.7mm. I think that is lost in the mists of time, but I guess the best solution is not to fit it?

Cheers,

David
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PostPost by: promotor » Fri Feb 24, 2017 8:25 pm

It is impossible to guess the reasons some people do things and you shouldn't make the mistake of thinking that there must be some method behind their madness - sometimes madness is behind their madness!

I stripped a 'box yesterday that had supposedly been rebuilt - it had an early type 3rd/4th synchroniser with early baulk rings but was fitted with late type block bars which are completely incompatible in every possible way. The only bonus was that the block bars were completely new! Bit of a bonus as they aren't cheap!

As for your box - don't try to second guess previous owners - just do the right thing for your gearbox. Leave the clip out (as you've already reached the conclusion that it isn't doing anything) - and you've checked the gearbox's operation carefully so it looks like you're on the right track!
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PostPost by: ncm » Tue Feb 28, 2017 3:50 pm

The answer to this is in the workshop manual . Unfortunately it is hidden in the fault finding section under 'gear lever vibration' :? Have a look in the wiki .
6. GEAR LEVER VIBRATION

Violent fore and aft forced vibration of the gear lever:

Using feeler gauges, measure the clearance between the over-run stop tube and the rear end of the 3rd/Top selector fork boss with 3rd gear engaged. This dimension should not be greater than .005 in. (.127 mm.). If it is in excess of this figure it will be necessary to fit a new stop tube (Part No. 2821E-7A072-B), and a graded clip so that the gap is reduced to less than .005 in. (.127 mm.). The graded clip has a basic part number of '2821E-7K714' plus a suffix which varies with the thickness. Do not fit a graded clip which is too large; this can lead to 3rd gear 'jump out. The Service stop tube is colour-coded RED. A plain tube without a circlip is fitted in Production. Circlips must not be fitted with the plain tube. Check the mainshaft end-float which should not exceed .030 in. (.76 mm.). If it does, check that the tab washer retaining the mainshaft nut is intact. The tab washer should prevent the nut from rotating . If the bearing is retained by a circlip ensure that the circlip directly behind the mainshaft bearing is correctly seated in its groove. Remove the selector mechanism and rails to gain access to the 3rd/4th synchroniser sleeve. Measure the run-out of the side of the fork groove, with the sleeve in the 3rd gear position, using a suitable dial indicator. Place a dummy propshaft on the end of the gearbox to simulate a load. The run-out should be measured while rotating the input shaft to simulate driving conditions. This should be repeated three or four times with the gear dog teeth engaging on different teeth on the sleeve. If the run-out. exceeds .020 in. (.51 mm.) the synchroniser assembly should be renewed.

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