Lotus Elan

Gearbox overhaul, synchro and shift fork material

PostPost by: benymazz » Sun May 09, 2021 3:33 pm


While I have the engine out of my Elan (again) in a few weeks I'm going to be overhauling the gearbox as "preventative maintenance" - it has almost 140,000 miles on it with no overhauls and has lived a hard life with several hot laps around Lime Rock and dozens of autocrosses. I'm not expecting to find anything totally destroyed, it still functions fine but the 1-2 shift is getting slow and notchy and occasionally (like once every couple months) it will pop out of 3rd on overrun (only at high rpms, above 5k).

The gear box is original to the car (1965) and a close ratio type. So far I have the following replacement parts on my list:
-All gaskets and seals
-Input shaft bearing and tail housing bushing
-Front and rear thrust washers
-Front and rear bearings
-Countershaft and needles (given the age I'm expecting to find damage in the countershaft bearing area as that seems like a common issue)
-All synchro rings
-Detent springs
-1/2 and 3/4 shift fork (again, expecting to find wear given age and past [ab]use)

Looking through the parts offered by the usual suspects there is a choice between the conventional bronze shift forks and the steel type. Is there any upside to using steel forks other than decreased wear? And is wear on the normal bronze ones common enough to warrant using steel ones?

I also see a choice between the normal brass synchros, steel synchros, molybdenum-coated synchros (from Kelvedon), and synchros with a mystery "special coating" from TTR. Has anyone used any of the more exotic ones? Is there a distinct advantage over the brass synchros other than wear? Shift quality/speed and wear are my main concerns as I'm taking my Elan to a couple track days a year nowadays.

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PostPost by: SENC » Sun May 09, 2021 8:48 pm

Getting 140k miles out of the originals should be proof enough that the bronze/brass are sturdy enough, I'd think! Given the age and that it is a CR, I'd bet your gearbox is an early one - so be sure you get the right size early synchro rings and spigot bearing. My Seven S2 thread includes some pictures from when my CR gearbox was apart - may be useful.
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PostPost by: Billmack » Sun May 09, 2021 11:01 pm

May be some wear on the actual gear that pops out and the splinted collar that engages it. Maybe look at the little teeth and splines with a magnifying glass.
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PostPost by: rgh0 » Mon May 10, 2021 12:53 am

Bronze on steel is actually a better combination in sliding from a wear perspective such as shift forks on hubs or synchro rings on synchro gear hubs than steel on steel. The fact that the steel rings are offered with "special coatings" shows the wear issues they face

I think people use steel because in racing where some drivers are very brutal on the change and force the change through they can break the bronze components which are more brittle than steel. With normal driving on the road and even racing with a little mechanical sympathy the bronze components are fine I believe.

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PostPost by: joe7 » Mon May 10, 2021 1:30 pm

If its popping out of third gear it could be 1) the retaining cap causes interference - see WSM regarding where to cut 2) an incorrect 3/4 gear stop tube, too short, which is probably what's in it if it hasn't been rebuilt. Ford solved this problem by first using a "clip", then the proper length tube. See WSM for fitting specs. I would wait until I have the gearbox stripped down before ordering parts, you never know what you will find.
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