Lotus Elan

rebuilding close ratio gearbox

PostPost by: seniorchristo » Sun Mar 22, 2020 10:24 pm

Having time off work has afforded me the opportunity to rebuild my spare c/r gearbox. There is play in the splines where the 1st/2nd synchro hub fits over the mainshaft. Is there a Loctite bearing mount or similar product that can alleviate this play? Thanks
Chris :)
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PostPost by: Lyn7 » Mon Mar 23, 2020 7:02 am

Hi Chris. I cannot answer your question directly. I had a curious problem with a gearbox some years ago and went to the Loctite website. It appeared there were about 300 products , so I emailed them my question/problem. I had an answer inside 4 hours and no problems since!
Good luck, Lyn..
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PostPost by: 2cams70 » Mon Mar 23, 2020 7:17 am

It's a high contact stress area. If case hardened steel wears here there's no way any Loctite product will stand up. It's not a major problem in any case and won't cause any operational issues unless really severe. Did you mark the hubs before dissassembly? They wear as a set and it's best to always always match the splines up in their original locations.
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PostPost by: rgh0 » Mon Mar 23, 2020 9:01 am

Loctite 660 is intended for this sort of repair. Worth a try but debatable as to how long it will last. i know people who have used it on Europa rear wheel drive shaft splines with good success and these are notorious for wear.

cheers
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PostPost by: seniorchristo » Mon Mar 23, 2020 12:28 pm

Unfortunately I did not mark the parts and there were no existing marks as indicated in the workshop manual. I found a Vibra Tite product 802 large gap filler that mentions splines and has good reviews. I think I'll give it a try.
Thanks,
Chris :)
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PostPost by: joe7 » Mon Mar 23, 2020 2:13 pm

A simple idea would be to try the hub on in a different location. Also there aren't any marks on mainshaft for the 1/2 hub unlike the 3/4 hub so I guess it can be installed in any position. There should be an etched mark on the inner hub and a matching one on the outer hub to align the hub parts to their original position to each other.
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PostPost by: 2cams70 » Mon Mar 23, 2020 10:17 pm

If it's any consolation virtually all the boxes I've pulled apart have had some looseness in the splines here. Never has it caused any significant operational issues and never have I seen really extreme wear or failure here. If it were me I'd just leave it alone and reassemble. I would not bother trying to find the tightest point on the splines and reassembling in that position. This will most likely be the position where only the high points are making contact and therefore you will just be accelerating the wear rate.
Key thing if it is an earlier box with the big nut on the mainshaft is to make sure this nut is correctly torqued and use some red Loctite on it. Usual thing is for this nut to come loose which then allows the hubs to rattle around on the splines which accelerates wear here.
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PostPost by: seniorchristo » Tue Mar 24, 2020 1:48 pm

2cams
The gearbox is indeed an early type with the draw nut mainshaft and I seem to remember the nut being somewhat loose. I will heed your advice. Thanks! :)
Chris
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PostPost by: RichardHawkins » Tue Mar 24, 2020 9:09 pm

I have always had good help from Loctite in both my industrial life and when playing with cars. I agree that there are so many grades it is difficult to know which one to use. I phone the technical help line if in any doubt.

Many years ago I had a car with a 5 speed getrag box, that would slip out of gear. I decided an overhaul was needed. I changed all the bearings, but nothing seemed bad, I think I changed the bronze synchro rings, but can’t remember. The odd thing was I didn’t really find anything wrong. When I came to fit the drive flange at the rear of the box I tightened the large nut to the correct torque, but noticed that there was still axial movement. The nut was tight on the thread but not tight against the face of the drive flange. I little work with at thread file and the nut fitted correctly. I sometimes wonder if all I needed to do was tighten the nut correctly instead of taking the whole thing to pieces.

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PostPost by: seniorchristo » Wed Mar 25, 2020 2:55 pm

A couple more questions :roll:

1) Upon reassembly I can't seem to find the "oil slinger" that is shown between the bearing (item 3) and the gear on the input shaft. I don't remember if it was there when I disassembled it. It is numbered in the workshop manual but not in the Service Parts List shown below. Is it possible this part was not included on some early transmissions?

2) When pressing the rear bearing onto the mainshaft, is it pressed tight against the 1st gear sleeve? This would seem to stop the sleeve from spinning although it would still allow first gear to rotate around the sleeve's outer diameter.
Thanks,
Chris :)
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PostPost by: joe7 » Wed Mar 25, 2020 3:58 pm

Easy one. #1 yes & #2 yes. The main shaft nut should be torqued to about 25 lb which holds everything together. Forgot to mention the 1/2 bush should be locked onto the mainshaft by the little ball #7 which holds the bush in place to prevent it from spinning.
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PostPost by: Craven » Wed Mar 25, 2020 8:00 pm

Re oil slinger, I seem to remember that an oil return way in the nose/input shaft cover introduced early on. This may have negated the need for a slinger.
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PostPost by: seniorchristo » Wed Apr 08, 2020 9:18 pm

I have the gearbox mostly reassembled but I see there is an alignment difference between the mainshaft gears and the cluster gears. I would estimate it at about 1/16". There is also more clearance between the 4th gear synchronizer hub and ring by a similar amount. If the mainshaft gears and layshaft gears were aligned, this clearance would be similar in all four forward gears. This tells me the mainshaft isn't in the case far enough but the installed tailshaft housing holds everything in position with no adjustment allowed. Is this within tolerances?. The picture is not very descriptive but a staightedge shows up the difference. :) Thanks
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