Lotus Elan

No Reverse Gear

PostPost by: archigator » Wed Aug 12, 2015 9:51 pm

After a pleasant Sunday morning drive, I go to pop my Sprint into reverse gear and back it up the driveway. I got a bit of a grind, and couldn't engage reverse, so I drove it up the driveway headfirst without backing it in. The next Sunday i try to back it out of the driveway, and I get no grinding or any reverse gear at all! The car engages all 4 forward gears without an issue. The clutch master and slave cylinders are both working fine.

Any guesses as to what's gone wrong? I've checked the archives, but haven't found the same condition with a resolution
.
Thanks in advance for your input.

Gary
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PostPost by: CBUEB1771 » Thu Aug 13, 2015 2:49 am

Gary,
You should check the plastic, hemispherical cap that retains the gear lever. It may have backed off from the gearbox or be damaged. In either case, when you lift up the gear lever to engage reverse it may be all the way out of engagement with the reverse selector fork.
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PostPost by: elanfan1 » Thu Aug 13, 2015 8:54 am

The previous reply sounds the most obvious answer to your issue but if by any chance it isn't is there any possibility that the reversing light switch is in a bit too tight as this can prevent reverse being selected too. If it's been working up til now it is perhaps unlikely.

Good job it happened close to home.
Steve

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PostPost by: archigator » Thu Aug 13, 2015 11:44 am

Thanks guys. I'll have a look at the plastic cap this weekend.

If the gear lever is "all the way out of engagement with the reverse selector fork," would tightening down or replacing a possibly damaged plastic cap resolve the issue? I've never had occasion to work on the transmission before, so that's a bit out of my limited area of expertise. If there's no obvious issue with the cap... what might be a "less desirable" cause for reverse gear not engaging? (I doubt too that an overtightened reversing light switch might be a factor, as I've never touched it in any previous work, but I appreciate the heads-up as it being a possible cause.)

As always, thanks for your help.

Gary
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PostPost by: CBUEB1771 » Fri Aug 14, 2015 1:11 pm

If the plastic cap has come loose I would first remove it completely, along with the gear lever. Then make sure that the slots in the three selector forks are all in a line (neutral position), replace the gasket under the plastic cap and then reassemble. That should resolve the problem. If the plastic cap is damaged you will probably need to replace it. RD Enterprises offers aluminum replacements. The gasket under the cap is important as it also acts as a shim to control how far the cap can be screwed down. Without the gasket in place the cap can be screwed down so far that the end of the gear lever rubs on the bottom of the engagement slots in the selector forks and this makes selection of any gear difficult. The reversing lamp switch is a possible problem but agreed, not likely if you have never touched it. If either of these two items are not the root of the problem you'll probably need to take the gearbox out. There could be damage to the reverse idler or its selector fork.
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PostPost by: archigator » Fri Aug 14, 2015 6:16 pm

Thanks for your help. I'll have a look this weekend and see where it takes me. If the gear selector fork or reverse idler are damaged, would that damage be visible and obvious with the transmission in-situ, looking down upon it with the cap and gear shift lever removed?

BTW, I never cease to be amazed and greatful at the abundance of help and years of cumulative experience this forum provides. Thank again.

Gary
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PostPost by: CBUEB1771 » Fri Aug 14, 2015 8:56 pm

The reverse idler and selector fork are only visible by removing the top cover from the main case, hence that is only done with the gearbox out of the car. Fortunately these items are very robust in comparison to the plastic gear lever retaining cap and therefore much less likely to be the problem. The grinding noise you mentioned when trying to select reverse is nothing unusual. Keep in mind that selecting reverse involves jamming one straight cut gear into engagement with two other straight cut gears when one is probably spinning, no synchromesh assistance here. My gut feeling is that you will find the problem pretty quickly and that it will be related to the plastic cap.

I have been forgetting about the small lever which is part of the reverse selection system. I think this lever is retained inside the cast iron cover that forms the receptacle for the gear lever. That should be visible when the plastic cap and gear lever are removed. Unfortunately I don't recall exactly how that works. My gear box is out and on the garage floor at this point. I'll have to reeducate myself over the weekend on the function of that small lever.
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PostPost by: archigator » Fri Aug 14, 2015 11:34 pm

I pulled the cap off and pulled out the gasket, which is as thin as a sheet of paper. Any ideas how thick this stock gasket is supposed to be? Maybe it's just been compressed too thin.The cap itself appears to be okay.

Thanks,

Gary
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Attachments
Looking down at selectors.jpg and
Looking down at selectors with shifter removed,
Shifter and cap gasket.jpg and
Shifter, cap, and gasket
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PostPost by: Craven » Sat Aug 15, 2015 12:20 am

Hi,
Looking at the centre selector rail the grove seems to be well worn, as this pulls and pushes the 1st /2nd synchro hub outer ring, on which the reverse gear is made its possible this part is not being fully returned to the neutral position. Consequence being when the reverse idler gear is selected in reverse it does not engage correctly, if at all with this ring.
Using a suitable screwdriver move the centre selector rail back and forth, you should be able to feel a definite position when the hub is in the correct neutral position, refit the gear lever without moving the rail positions and try to engage reverse.
FWIW
Ron.
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PostPost by: CBUEB1771 » Sat Aug 15, 2015 3:59 am

I think Ron is on to the problem. The gear lever should not contact the bottom of the notch in the first/second selector fork or the reverse selector lever. In the similar photo of the gearbox in my +2 you can see that the copperslip compound I applied at assembly has not been wiped away by hard contact. I just checked two new gaskets and they are between 0.025" and 0.027" thick. I now remember Gary Anderson having gear selection problems and he determined that the plastic cap was running down too far and causing hard contact of the bottom of the gear lever and the selector forks. I believe he solved the problem by using two gaskets under the cap. This can also cause problems with selecting reverse because you might not be able to pull the gear lever up enough to engage into the reverse selector lever. I also added a photo with the tail housing cover removed for a better view of the selector forks and a photo of the underside of the tail housing cover so you can see the reverse selector lever I was talking about earlier. This lever is essentially an extension of the gear lever.
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IMG_0688.jpg and
IMG_0686.jpg and
IMG_0684.jpg and
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PostPost by: CBUEB1771 » Sat Aug 15, 2015 4:04 am

Oh, there was one more photo on my phone. A new toy that appeared at the office garage today. Just for amusement!
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IMG_0682.jpg and
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PostPost by: archigator » Sat Aug 15, 2015 11:09 am

We are amused!

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PostPost by: Craven » Sat Aug 15, 2015 12:06 pm

New Gasket is around 0.015 - 0.017" thick
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PostPost by: archigator » Sat Aug 15, 2015 2:45 pm

I read elsewhere on this site that the gasket was 0.035", so I just made a 0.032" gasket sandwich... two layers of ruberized 0.08" gasket with a 0.16" cork gasket filling. Glued together with Gorilla epoxy. Yum!

So now I'm getting mixed messages... 0.016" or 0.035" gasket? :D

Gary
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0.032 Gasket Sandwich
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PostPost by: Craven » Sat Aug 15, 2015 3:49 pm

What was the thickness of the one you removed? The depth of the gear lever is fixed by the Pivot Pin anyway.
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