Im thinking exactly of the circlip failure, I however didnt realize its inside the transmission, I thought it was in the bellhousing (Snip)....
You only have to remove the two output shaft housings and the bell housing in order to replace the circlip. In the parts manual drawing of the shafts and gears, it's item 3 to the left end of the second row of parts. It snaps into a groove just inside the hollow left end of primary shaft 8.
When the bell housingis removed, the hollow end of the primary shaft is protruding through a ball bearing in the gearbox wall, and you can access the circlip there.
Prior to assembly, lube both mating splines with a moly grease, or with Anti-Seize. Install spring 2 into the end of the Primary Shaft. Install the Input Shaft's splined inner end into the bore/ female spline in the Primary Shaft. Push it in with sufficient force to compress the spring. Once the Primary Shaft in in far enough to expose the circlip groove inside the bore, install teh circlip. Now put the differential assembly bits, bell housing and output shaft housings back where you found them. Details are in the Service Notes, Section F, Transmission.
It's not a trivial job, but it doesn't require dismantling the gearbox proper.
3 hours to remove the transaxle.
10 minutes to drain the gear oil.
1.5 hrs to R&R the output shaft housings & bell housing.
5 minutes to R&R the circlip.
3.5 hrs to replace the transaxle... plus adjustment time.
Circlip and two output housing gaskets required (cheap).
Inspect the release bearing prior to re-assembly. The clutch doesn't have to be removed for the circlip job, but it's quick to remove. Do so and you can also inspect the spigot bearing and clutch disk. Don't pass on the opportunity to re-new them if they're old or worn.
Lotus Owners Oftha North (LOON)