Lotus Elan

Jumping out of 2nd gear on the overrun

PostPost by: lotusfan » Sat Mar 02, 2013 2:58 pm

The problem is as the title says. This is a 4 speed gearbox that I rebuilt with new bearings and seals during a major rebuild, I do not know if it had this problem before the rebuild. Having read the archive and the WSM I decided to check the length of the selector springs as defined in the WSM, it says they should be 0.335 - 0.375 in above the gasket. Having measured them I find that all 3 are 0.025 in below the minimum required dimension. On the face of it that is the cause of the problem and all I have to do is to add a 0.048 in shim as described in the WSM to bring the length of the spring into tolerance. However it does not seem as simple as that for the following reasons:

1. All 3 selector springs are too short but it only jumps out of 2nd gear so should I add shims under all 3? If yes, why?

2. It was possible to hold it in 2nd gear on the overrun but an extreme amount of muscle was required, is adding a 0.048 in shim eqivalent to this?

3. I also intend to check the detent slots in the selector rod for wear but is there anything else I should be checking? I obviously missed the spring length issue when I rebuilt the gearbox but the synchromesh cones and selectors are good and the nylon retaining cap of the gear lever does not interfere with gear selection.

Any thoughts you have please before I add a shim under one spring and put it back together again.
Mike
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PostPost by: prezoom » Sat Mar 02, 2013 4:31 pm

Upon checking my springs, they also were on the short side. I probably should have replaced them, but instead, I stretched the springs by bending the spring over itself in different directions until the maximum specified length was achieved. Slipping an appropriate feeler blade between the coils, helps in the stretching process. After about 4 years, everything is still working as it should. Shimming the springs, may cause coil bind, if in excess. If you choose that route, be sure to check the gear lever movement prior to reinstalling the transmission.

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PostPost by: Chancer » Sat Mar 02, 2013 5:47 pm

It is most likely to be worn teeth on either the collar that slides over the baulk ring that engages the 2nd gear (sorry cant recall the name) or if you are really out of luck the mating ones on the gear itself.

I dont mean the helical gear teeth but the short triangular shaped ones on the gear and/or the corresponding lands around the splines on the collar.

terrible description I know, if I had a manual to hand I could do a better job.

If these are in good condition then only a very slight detent spring pressure will maintain the vehicle in gear.

The wear is usually caused by driving with a worn out synchro, crunching on downchanges or repeated quickshifting that beats the synchro action, TBH thats pretty hard to do with a 2000E box, the 5 speed T9 is more likely to suffer that fate if the baulk ring doesnt crack first.
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PostPost by: StressCraxx » Sat Mar 02, 2013 5:52 pm

Another possibility:

From the Lotus West Tech Manual
"When Tranny Pops out of 2nd Gear"
- by Ron Brown.

There is a large hexagon nut on the tail shaft by the speedo drive gear. There is a tab washer that holds the nut tight. However, if the tab washer was not peened over to lock the nut in place it may have come loose. The slop will allow the entire first and second gear to shift and second gear does not fully engage.

The trans must be removed, The tail shaft housing and shifting forks must be removed to tighten the nut and peen the tab washer over the nut to lock it in place. I can scan the page and email it to you if desired. The transmission section of the manual is needed as well.

Regards,
Dan
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PostPost by: Chancer » Sat Mar 02, 2013 8:40 pm

Yes that reminds me of another 2nd gear problem that I once had.

I had broken a tooth on the layshaft and at the time could not find a replacement other than a reconned box from a then well known transmission specialist, it never quite felt right and the gear selection was not as slick as normal, it got noisier and 2nd and 3rd often would jump out or refuse to engage but once in would hold on power and overrun.

When it got too bad I stripped it and found that the rear main bearing retainer circlip had not been correctly engaged and had come out of the groove allowing the mainshaft to move away from the 1st motion shaft.
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PostPost by: lotusfan » Wed Mar 06, 2013 6:30 pm

Gentlemen - thank you for your replies.

Rob - I had worried about adding a shim because of coil binding but stretching the spring sounds like a good idea, thanks for that.

Chancer - I will check the area I think you are talking about.

Dan - I have what is called a snap ring main shaft, no nut, but worth checking Chancers next comment about a loose snap ring. If there are any other clues in the Lotus West Tech Manual I would welcome a copy.

More digging and checking is in order.
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