Lotus Elan

No Reverse Gear

PostPost by: archigator » Sat Aug 15, 2015 5:07 pm

The one I took out was about 0.006". But I guess it has been compressed for about 40+ years. Although it appears pretty distorted from the pressure, I'd say it's doubtfull that it was 0.035" to begin with.

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PostPost by: Craven » Sat Aug 15, 2015 5:33 pm

I have difficulty in following the gasket thickness argument anyway, the cup & ball arrangement for the gear lever is spring loaded in the downward direction, and as far as I can figure changing the gasket thickness will only marginally change the spring loading of the ball joint.
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PostPost by: archigator » Sat Aug 15, 2015 6:05 pm

I'm inclinded to agree. Any benefit would appear to be quite marginal. I just tried the 0.032" sandwich gasket, and I still couldn't get reverse. Now to make a 0.016" gasket. In my case, the higher gasket makes the plastic "cup" sit higher and seems to conflict with the shifter operation around the open top neck of the cap.

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PostPost by: Craven » Sat Aug 15, 2015 7:08 pm

I think this is a blind alley, the gasket thickness that would make a difference to the rail slot / gearlever location would be the one between the turret and the tail case.
Your problem to my mind is rather more serious, this won?t help much but main components involved in reverse gear operation are, small straight cut gear part of the lay shaft, idler gear, the large straight cut gear made around the 1st/2nd synchro hub & the reverse gear selector fork.
Failure of any of these is a gearbox out I?m afraid.
I would drain the gearbox oil and look for evidence of broken gears.
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PostPost by: gjz30075 » Sat Aug 15, 2015 10:31 pm

Gary, with the gear stick out, box in neutral, can you take a large screwdriver and push the reverse
rod forward and engage the gear? That should determine whether its the stick position or the gearbox.
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PostPost by: CBUEB1771 » Sun Aug 16, 2015 2:27 am

OK, just back in from experimenting with my gearbox. I am going to have to retreat from my gasket thickness argument but not for the reasons that have been set forth earlier today. The gasket has a one-to-one relationship with how far the gear lever can be pulled up long its axis before it is stopped by the plastic cap. The thicker the gasket the longer the possible vertical travel of the gear lever. Remember that the gear lever has to be pulled up into order for it to engage in the reverse gear selector lever. I took the gasket out and ran the plastic cap all the way down onto the tail housing cover and found that I could still select reverse, but only just. The 0.027" thick gasket makes engagement of reverse more comfortably attainable. The new gaskets I measured are aftermarket, we don't know what the design thickness is without seeing an EnFo drawing or checking a genuine NOS gasket. The "pivot" pin mentioned earlier does not establish the depth of the gear lever fitment in the tail housing cover. That depth is established by the semi-spherical surface machined into the tail housing cover and the mating surface on the gear lever. The "pivot" pin is a good 1/8" clear of the bottom the machined slot in the tail housing cover. This clearance is necessary to allow the gear lever to pivot from side-to-side in order to align with the first/second, third/fourth and reverse selector rod centerlines. I put "pivot" in parentheses because the function of this pin is to prevent the gear lever from rotating around its long axis while not impeding pivoting in the fore-aft and side-to-side degrees of freedom. I agree that trying to select reverse using a long screw driver is the logical next step.
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PostPost by: Craven » Sun Aug 16, 2015 6:59 am

You are correct in that the pivot pin does not as I suggested determine the working depth of the gear lever, however I think you are overlooking the spring between the cap and the ball top.
It retains the ball into the cup and returns it after reverse gear is used, in order for the gasket thickness to limit the gearlever movement upward the spring would need to be fully coil bound I don?t think this should happen or been designed to operate in this way, the gasket thickness will simply change the static or preload on the spring. It?s unlikely this non critical assembly would have a close tolerance specific gasket, the one I measured was from a genuine Ford set.

P1020904.JPG and
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PostPost by: el-saturn » Sun Aug 16, 2015 7:29 am

good morning europe! as far as i remember, mine doesn't even have that gasket: so it can't be all that critical! sandy from the rainy alps. ...................back on the road after 1 month of abstinence (29kmh too fast on nov. 28 last year!!)
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PostPost by: CBUEB1771 » Sun Aug 16, 2015 4:59 pm

Ron's value for the gasket thickness, 0.015" to 0.017", would seem to be correct. The vertical travel of the gear lever is not controlled by coil binding of the spring under the plastic cap. The ball end assembly has three turned diameters. The largest diameter section will not pass through the hole in the stamped metal retainer and this hard stop sets the upward limit of travel with respect to the plastic cap. The spring is still about 0.020" away from coil binding at this hard stop. Therefore the height of the plastic cap, when installed on the tail housing cover, does have a definite effect on how high the gear lever can be lifted with respect to the reverse selector lever and this is affected by the thickness of the gasket. However I have already accepted that the gasket was clearly not intended to be a means of adjusting the selection of reverse gear.
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PostPost by: Craven » Sun Aug 16, 2015 6:10 pm

It can only be a matter of academic interest now as I don?t think we have helped Gary much with his reverse gear problem.
The attached pic shows the position of a gear lever end in the reverse gear lever when the gear lever is at its maximum lift, the gap seen at the end of the gear lever is about 0.115?, reduces to zero when lever is released. Significance being this is WITHOUT a gasket (Sandy) at all and therefore in this example there would be no clearance problems engaging these two parts with any thickness gasket. As for the maximum gasket thickness with respect to the engagement, the cap can be undone completely and gear lever will still be within the slot in the reverse gear lever.
FWIW
Ron.

P1020907.JPG and
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PostPost by: archigator » Sun Aug 16, 2015 6:27 pm

Which of the selectors is reverse? (Before I start pushing things about with my screwdriver.) Obviously, I've never disassembled a transmission.

Thanks!

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PostPost by: Craven » Sun Aug 16, 2015 6:34 pm

The one on the right hand side as viewed in your pic
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PostPost by: TroonSprint » Sun Aug 16, 2015 6:58 pm

Which of the selectors is reverse?

You need to think of the movement the lever makes. To select reverse you move the lever left and back. Since it pivots on the ball and cup, the business end of the lever must be moving right and forward, the opposite of what you are doing. Therefore the selector is the one on the right (as Craven said) and to select reverse you need to push it forwards.

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PostPost by: archigator » Sun Aug 16, 2015 8:38 pm

I pushed the gear forward with the screwdriver, the selector lever goes forward and pops up a bit...and the car goes into reverse. A good thing, yes?

So can I now attribute the issue to the position / installation of the shift lever? Meaning that the gears and selectors are okay?

Thanks,

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PostPost by: CBUEB1771 » Sun Aug 16, 2015 9:00 pm

This sounds encouraging. The reverse selector lever pivots from a location up in the tail housing cover so it will lift up a bit when you ease it forward. Have you done this a few times and gotten reverse repeatedly? I was beginning wonder if something had come adrift where the reverse selector pivots but it seems that is OK. Why not just reassemble the gear lever at least temporarily with no gasket and see if you can select reverse? I don't see anything obviously wrong with your gear lever and plastic cap from the earlier photos.
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