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Esprit Turbo project car - part3 - the further continuation - Page 181 - Esprit 'Project & Restoration' Room - The Lotus Forums Jump to content
Lotusfab

Esprit Turbo project car - part3 - the further continuation

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Gearbox

Ok there are lots of threads on here about gear problems, but no detailed analysis- explanation of how it all works. When I put it back together I did not really need to understand the shafts, as the selector positions are fixed. The bolts locate them in holes in the shafts. However, now there is an issue it's time to understand how this all works. I could be wrong (disclaimer!) as I have not experimented with it yet(that will come later), but this is what I believe happens......

IMG_7708.thumb.PNG.87eb99a46a49d7d6ee2d311508b2503e.PNGHere's the selector shaft. The gear change lever mechanisms simply  push it into the gearbox, pull  it out and rotates it to get the gears. So you can do this by hand to select gears for tests. That's what I did and it all worked perfectly until I bolted the engine on!😡😡IMG_7707.thumb.PNG.23987f687d4f164cec0b1f71900932bf.PNGThe short lever(bottom of top picture) on the shaft actuates the selector shafts 1/2 and 3/4 gears.  The longer one near the crank arm does 5/Rev. So far easy! The spring in the centre keeps the shaft sprung to the 3/4 selector fork position. So rotating the crank without pushing the selctor in or out of the gearbox will engage 3/4. 

When the shaft is pushed into the box the short selector arm leaves the 3/4 selector fork and aligns with the 1/2 shaft cut out. Then  rotating the selector lever with push the 1/2 shaft  engaging 1/2 gears. Only one shaft can move at a time due  to the interlocks.

So the troublesome reverse. On the right hand side of the bottom picture you can see where the longer selector arm fits. I have called it shaft in the above and labelled it yellow -sorry! 

 

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Reverse - not sure about this, maybe someone could confirm? I will be sure after I have taken the top off the box! 

IMG_7710.thumb.PNG.829b6d3b7688e6c695b440d6ed335cb7.PNGI believe the long selector shaft arm sits in the rectagular gate (top right) . For 5 th the arm is in the retangle bit and pushes the rectangle to the left to engage 5 th gear. When you select reverse,buy pulling the selector shaft out of the gear box, (not sure about this next bit) the arm moves through the gate and engages with the fork on the reverse shaft. When you then rotate the arm it pushes only the reverse selector leaving the rectangular bit stationary. 

The position of the rectanglular bit and ref fork on the shaft is fixed because the bolts locate in holes on the shaft. The only adjustment is the position of the reverse gear, which is set using a measuring tool.

So why can't I engage reverse? Well the easiest solution would be if the gear teeth are not meshing on the idler and reverse gear because the are in the worst possible meshing position( very unlucky if this is the case). Then rotating the engine would fix it.

I can feel the arm moving through the gate detent but then it's stuck. This could also be because it's jamming in the edge of the rectangular bit and nit cleanly passing through the gate. Why because the selector arm is slightly bent as David said. 

If the engine rotating doesn't fix this I shall remove the selector shaft and experiment. Then if I still can't get it to work the top cover will be coming off. I will post the solution here and confirm operation of the reverse gear, unless someone else can confirm this post is correct? Thanks.

 

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That all seems correct. Is the adjustment of the long fork which moves the reverse idler correct? The two clamp bolts holding it onto the shaft? Thinking about rotationally rather than axially on the shaft.

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Yep that's a good point. I was thinking about that also. There's no mention of any rotational adjustment in the manual, as far as an know. But we all know there are glaring emissions! Not sure if the rotational position is adjustable. Will look into it if an cant get this working, theoretically if the shaft is rotated it could jam the long selector arm as the gap would be reduced.

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Here's  better picture. I wonder how many reverse gear problems are to do with tthis gate? IMG_7711.thumb.PNG.6e8736bed5b8e800eac8b3fa27f43260.PNGIn the picture the bolts are out.for the selector arm to pass through the gate smoothly the edges need to be aligned. But also notice the rotation of the reverse shaft. If as in the picture the reverse shaft is rotated towards the rectangle the width the slider arm has to slide is reduced. It seems plausible the gap may not be wide enough which would impede reverse selection. I shall remove the shaft from my gearbox and take some pictures. If I need to adjust the fork the top will have to come off. A pain but not that difficult.

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IMG_7712.thumb.PNG.37a83ad8d1c5576997a6aaabb932af2d.PNGHere's my finished box. You can see the edges of the gate arn't perfect. They are set by the bolt detents in the shafts. Maybe a small adjustment is possible. I could rotate the reverse gear selector fork at the other of the shaft to increase the gap for the selector arm. A photo of this on a working box would be a great help if anyone has one?

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If you give me an hour or so - I'll give you pics of 2 working boxes from the top?!!

 

Edited by 910Esprit
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Thanks Steve. I'm not sure my description of the reverse is correct. It's possible the selector arm always stays in the rectangle which tilts to allow the arm to move reverse shaft only. I will have to remove the top cover and explain on here. 

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1 hour ago, Lotusfab said:

Here's  better picture. I wonder how many reverse gear problems are to do with tthis gate? IMG_7711.thumb.PNG.6e8736bed5b8e800eac8b3fa27f43260.PNGIn the picture the bolts are out.for the selector arm to pass through the gate smoothly the edges need to be aligned. But also notice the rotation of the reverse shaft. If as in the picture the reverse shaft is rotated towards the rectangle the width the slider arm has to slide is reduced. It seems plausible the gap may not be wide enough which would impede reverse selection. I shall remove the shaft from my gearbox and take some pictures. If I need to adjust the fork the top will have to come off. A pain but not that difficult.

 

1 hour ago, Lotusfab said:

IMG_7712.thumb.PNG.37a83ad8d1c5576997a6aaabb932af2d.PNGHere's my finished box. You can see the edges of the gate arn't perfect. They are set by the bolt detents in the shafts. Maybe a small adjustment is possible. I could rotate the reverse gear selector fork at the other of the shaft to increase the gap for the selector arm. A photo of this on a working box would be a great help if anyone has one?

NB these posts could be incorrect! I can't edit them. We will know when I get the gearbox top off.

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Hopefully Steve pics will explain this, if they don't I'm going to take the cover off put a camera inside the box and confirm how the reverse selector works. I just found this pic, IMG_7713.thumb.PNG.809ce73f8cdfa90d89996f60a5af279b.PNGwhich  was taken prior to the dismantelling. You can see reverse is engaged. If this is assembled correctly it shows the selector arm remains inside the rectangle. But if that is the case why have a cutout? Hopefully Steve's pics will explain more.

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Think I may have a solution! The manual says the notch in the operating dog on the reverse shaft should be verticle. I used the manual and a combination of the pictures I took to reassemble the box. I think the above picture shows the reverse shaft was incorrectly assembled. When I bought it as a non runner it was impossible to select reverse. I put it down to cable adjustment. Maybe it was put together wrong! As the rebuild emulates this it's also wrong. Just need a picture of a working box to confirm the notched operating dog is verticle and I have a relatively easy fix, fingers crossed! IMG_7713.thumb.PNG.1cb8708126f308ec2710b5842c3201e1.PNGAnd if this picture above is wrong then my explanation of how reverse works is probably correct! I know it's boring but just something  that has to be resolved. Here you go!IMG_7715.thumb.PNG.53fe1d5f0c60d48cc8fd805008e961a8.PNG

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IMG_20190803_162403.jpg

IMG_20190803_162418.jpg

Let me know if you need any other angles -  That box was in my car for last 5 years or so, just removed as 5th gear starting to whine a little

Edited by 910Esprit
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IMG_7717.thumb.PNG.fb32a2ae113808f7cbdc38ff92c767a6.PNGEureka! Thanks a lot Steve that picture confirms the operating dog on the reverse shaft should be verticle. I'll take the top off and reset it then a clean Loctite 518, job done! Thanks very much. It makes perfect sense how it works now and explains why I struggled to comprehend how my gearbox worked! 

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So it is the rotation of the shaft on the long fork which is wrong, as the dog is a fixed position on the shaft.

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Yep all dog positions are fixed by the bolt in the shaft detent.  The long fork which positions the reverse gear is one of the only things you can set. It can move rotationally and longditudinally. So all I need to do is mark the position on the reverse shaft. Loosen the bolts and rotate the dog to verticle. Then tighten the bolts. Job done! Maybe this explains why reverse is a problem for so many. The fork position may be wrong making reverse selection difficult or impossible. I suppose the bolts could come loose and slip over time. Especially with enthusiastic drivers heaving on the gearstick! 

I look forward to a very refined gearchange on this car!

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8 hours ago, 910Esprit said:

IMG_20190803_162403.jpg

IMG_20190803_162418.jpg

Let me know if you need any other angles -  That box was in my car for last 5 years or so, just removed as 5th gear starting to whine a little

Steve, when you have a spare moment  please could I have a picture of the reverse gear. Just want to check that mine is in an identical position visually on the reverse shaft. Thanks.

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6 hours ago, Lotusfab said:

Steve, when you have a spare moment  please could I have a picture of the reverse gear. Just want to check that mine is in an identical position visually on the reverse shaft.

I took this one yessterday, you can also see the witness mark on the cog, where it engages.  I'll take an engaged version a bit later

IMG_20190803_162351.jpg

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IMG_7774.thumb.JPG.dd323f01ea57cfa58e0fe4946ac5e537.JPGHello all, yes I am still building this,I had a short break! 

Gearbox

Well cover is off and this is what I found.IMG_7771.thumb.JPG.e5434ce33ef102c8116f128f0ef46bc4.JPGIMG_7772.thumb.JPG.47f1422af4184327d6412c8d8e98d985.JPGdifficult to see, but I had set the reverse gear position correctly. Also note the reverse shaft dog is only just if the verticle and nit enough out to baulk the selector mechanism. I have however reset it to exactly verticle as this will increase the separation of fifth and reverse gear, making it more distinctive at the gear lever. The gear selector engages reverse when selected manually with the cover off. So the engine orientation etc is not the problem. The fault must be in the selector shaft. So I tested it.

The fault lies with the cross shaft itself.

Top picture. You can see the shaft is corroded I cleaned up the relevant parts previously, but not well enough. When I tested the shaft it travels all the way in easily when 1/2 3/4. 5 is more  difficult but once the shaft has rotated to the reverse position it jams on corrosion as the shaft tries to slide past the rubber seal. Solution, new shaft or try extensively polishing it! Any other ideas out there? This gearbox really is very simple which I suppose is the genius of it. The Loctite 518 I have to say seems to have worked really well, although it hadn't been exposed to much oil yet. Shame to have to take it apart! 

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You can see similar corrosion on my selector shafts (photos above), which has just been polished smooth with use.  That gearbox had very rusty brown oil when I bought it, which I flushed a numer of times (out of the car) with parafin.   It then served me well for another 5 years and is still perfectly useeable.  

They do seem prone to contamination, which presumably could come from the breather, but some also seems to get in from the bellhousing 'open' input shaft.   Its probably one of the reasons why annual oil changes are specified, but probably rarely happen.   All I'd do is strip down and clean and polish that shaft with something like a scotchbrite.   It will be absolutely fine.  A new part (if available) would not be a good use of your money!   Loctite 518 is fine for that application.

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Thanks Steve. Are the welds normally there to hold the spring? They don't look right? 

Still they shouldnt affect the mechanism.

Just had a look at the above pics I'll try polishing it should work enpven thoughbthe shaft is pitted slightly.

I can always test it and if no joy plan B!

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Funilly enough, I was cleaning the residue sealant off a top cover yesterday and just thinking how crude those welds were!.   So safe to assume they are 'as desiggned!)  I'd take you a photo but I'm not at home at the mo

Hang on  - I've found one on the computer...

IMG_20190803_162618.jpg

Edited by 910Esprit
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Thanks for that, surprising how this was made. Well I need to get on and polishbthe shaft up. I did it before but not well enough! This time I going to put the oven on without sealant and getvthe reverse working before the final fix. 

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