Gearbox problems

[peteoddcar]

Hi Bob
Thanks for the tip - I had the driveshafts out to replace them, (inner joints knackered) so needed to change the oil so I took the chance to inspect my nuts although the gearbox seemed OKish, perhaps a little more effort that my daily driver Ford. Turns out that the nuts were tight and staked properly so that litle worry bead can be put back into the drawer so to speak. I am a great believer in prevention is better than cure.
I used Castrol fully synthetic Syntrans 75w90 which on the short test run seemed to have made the gearchange a lot smoother.Hope that's the correct oil
The effect of the repacement driveshafts is amazing... it now drives as it should.
The reason for the shaft failure was that at some point in previous ownership the clutch had been replaced, the shafts split at the innner tripod joints and no clips being fitted to the boots - the rollers and needles were RUSTY!!!.

So all out there, be sure have a good look at the boots/clip and replace any damaged ones pronto. Both outer joints are in good condition so I'llhang on the old shafts as spares.

So now I need to concentate on interior rattle suppression.... Should keep me busy for quite a while.

[JPope]

I spoke to Gerald at GST today, car was in getting the oil leak fixed, and I asked him about this specific issue and I now understand what is going on.

When the nut/nuts come loose if it/they back off too much it allows the shaft to move and that allows shims to drop down a step in the shaft, not sure if it main shaft or lay shaft forgot to ask that.
If this happens when you re-tighten the nut it causes the gear train to jam as the gears are not in the correct position.

His fix is to slacken the nut and briefly run the engine which spins the gearbox and with a bit of luck the shims end up in the correct position then tighten the nut again.
Bit fiddly but it save taking the box out, also he mentioned the fact these nuts are of the stake variety and should be changed as you need to re stake them much the same as the front hub nuts.

Bob

so how do you know when the shims are back in the correct position? tighten the nut/nuts and see if it will go into all the gears?

[RayD]

Hi JP,

The information about the shims is probably wrong ... you'll understand if you read all of the thread.

I haven't read it for a while but Dave Speck's information on the gearbox problems will be more reliable.

Ray

[John_W]

Having polished the car especially for the Lotus 70th event, I set off happily on Thursday morning on the 500-mile drive to Hethel, however I only made it as far as Stirling (125 miles) before I lost all gears except 5th (and 1st if you cut the ignition while stationary) and had to limp back home.

I think the attached photos are fairly clear in showing what the reason was.

The nut on the left shaft (ie towards the front of the car) had broken its peened-in collar and loosened by several turns, allowing the gear wheel to move out towards the end of the shaft. Both the gear wheel and the nut then proceeded to chew up the bolt heads holding on the lubrication channel and the channel mounting. The only thing stopping the gear nut falling off onto the road was the alloy cover plate to the gearbox. There will be lots of metal bits in my gearbox (some are inside the end cover).

The nut was completely loose, such that I could turn it one complete revolution by hand before it contacted the gear; this still did not place the nut fully back onto the shaft (compare the length of shaft protruding past the nut on the RHS shaft with the length of nut sticking beyond the end of the LHS shaft). There is a gap on the "car" side of the gear (as opposed to the "suspension" side) - maybe there is meant to be. I have not just torqued up the nut to move the gear back in, as I'm thinking about my next move.

I first mentioned this problem on the LEC club stand/tickets thread and Pinky and Brit-Car-Nut correctly identified the problem and pointed me to this thread. Thanks.

I now just need to hope that I can sort it on my own.

John

[Enright]

Nightmare. Can only hope that it's a cheap fix with no permanent damage.
With a bit of luck you might get away with just buying a new big nut, 3 replacements for the ones that got partially ground away, and some gearbox oil.

Regarding the bits of metal floating about in your oil, here's a thought:
While the hope is that most of the bits will come out with the old oil, I wonder if it would be possible to retro-fit a magnet to your gearbox drain plug so that any other potentially dangerous particles that don't get flushed-out get captured?
Or buy a magnetic drain plug? I know they exist - it's just a case of if you can get one the right size.

[John_W]

It was all going well until I found this:


Anybody got a spare 5th driven-gear or any suggestions?

Is it worth fixing or is it a new gearbox job, given the bits of metal in the one I've got?

John

[Brit-Car-Nut]

That is the Output Gear.
If the input gear is also chipped, you would need A100F6200S which is £183.28
Then the gear you are showing is A100F6239S which £226.08
The Baulk Ring is A100F6155S which is £80.69
For a total of £490.05 + VAT
Then, you will need a gasket kit and most likely will want to replace the seals and other oddities that you deem important.
It will all depend on what you can find as a replacement gearbox.

for what it's worth, I have several gasket sets that include the seals and you can have one for the cost of shipping.

By now, Steve S. (DVB) will have seen your plight and will put up an expensive gearbox on eBay where, right now, he is only offering a couple of engines with gearboxes.

[John_W]

John,

Is the price you're quoting from Lotus? I must admit I haven't tried them. I've looked at SJs & SW Lotus online and neither have the driven (output) gear listed, only the drive (input) gear.

By now, Steve S. (DVB) will have seen your plight and will put up an expensive gearbox on eBay ...

Now, that's what I call service!

John

[Brit-Car-Nut]

As usual, I just checked the parts at SJs for inclusion and price.

SJs shows them in stock

A100F6200S is still good in the current Lotus Price Book
A100F6239S went obsolete in 2017 - Sorry.
A100F6155S is still good in the current Lotus Price Book

Sorry, I purge my inventory when I sell out of something. I don't know why SJs wouldn't.
I honestly wasn't looking for quantity when I searched, so missed the N/A

[Brit-Car-Nut]

I make no promises, but the GEO Storm SINGLE CAM shows the same gear ratio in 5th as the M100.

I might be able to put my hands on a fifth gear from one of those.

[John_W]

Interesting!

I wonder how it could be established whether or not they are the same. Any pictures available anywhere to start with?

John

[Brit-Car-Nut]

Just something about 41 teeth?

[John_W]

Mine’s got 34 (well, 33 1/2).

[Brit-Car-Nut]

Oh well, Can you rotate the gears and see if the other gear is also broken?

I just checked and the gears of the transmission are all the same for both the NA and Turbo models.

I have a NEW (Lotus Training Unit) "LAA" gearbox (That's for the NA, The "LAX" is for the Turbo).

I also have several new Locking Nuts and a few gearbox gasket kits (from GM).

If any of that will help you somehow, let me know

[Enright]

John, some years ago I obtained a gearbox. I think it was some sort of pre-production variant that Lotus were selling off cheap.
It's been kicking about in my garage for about 10 years, and I don't even know if it would be compatible, or has the correct internals.
But if it will get you out of a hole, then you can have it until you can source a replacement for me at a reasonable price.
All I would want is for you to cover the shipping, unless we can use our LEC network to somehow get it to you.
Drop me a PM with your number and we'll see what we can do.

[John_W]

Neil,

That’s a kind offer. If I can’t get a replacement gear I’ll drop you a pm. Fortunately I don’t need the car as a daily driver, so I can afford a bit more time to look for the part. Meanwhile it’s dry and secure in my garage.

If anybody has a 5th gear in their back pocket, or knows where I can get one, give me a shout.

John

[John_W]

Can you rotate the gears and see if the other gear is also broken?

John,

As the photo below of the drive (input) gear shows, its teeth have no damage whatsoever (although the ring milled on the gear face at the base of the teeth looks strange). Also, there are 41 of them, which tallies with the Geo Storm 5th gear wheel you mentioned above so it sounds like what you found is the drive (input) gear.

Would you mind checking the availability of Geo Storm gearsets again and seeing if there is a driven (output) gear with 34 teeth? And the cost?



John

[Brit-Car-Nut]

I will see what I can find when I get back to the shop in a few days.

[Brit-Car-Nut]

John:

Can the gear(s) be removed by just removing the rear cover and removing the nut(s)?

I have a partial GEO gearbox that I can pull apart simple things, but I am not up to breaking the case apart again, right now.

If I can pull the gear(s) through the back, I would check the GEO one first and if it is wrong, I can also pull the gear from the Lotus training gearbox, but I am limited physically, so don't want to get started on something I can't finish.

Also, is your rear cover damaged - ground up?

Maybe you could PM me a daytime phone number that starts with 01 ????

JC

[John_W]

John,
That is very kind of you to offer, but I don't want you exerting yourself until you have recuperated a bit, so I'm not going to answer your questions or give you my number until you're better.

I am currently phoning around people in the UK to try to source the part. I'm not in any particular rush, as (like I mentioned to Enright) the car is happy in my garage until I get the bits to put it back together. However I will follow up this discussion with you later, because it is well worth knowing if the GEO parts are compatible, and if you have examples of both boxes then you're the man to find out!

Thanks for your help,
John