gearbox failure

[alatif]

gearbox went bang in 4th at oulton a few days ago. am looking at the jubu gearset. anyone tried it?

Regards Amer

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From reports across the pond all you do is move the weak point from the gear set to a different gearbox component.

For example, people have found that the engagement rings are the next point of failure and after that the actual gearshift has been found to flex.

You can still break the stronger gears as the oil temps get way to high without a cooler.

To be honest, with a stock 211SC you may be ok 260 is about the limit but you could still do with a cooler to help out the gearbox oil- doesn't matter how strong try are if the oil is starting to breakdown.

How long are your track stints?

[alatif]

I very rarely do more than 10 to 12 laps. This is what is usually recommended by trackday organisers. Since April 09 when I bought the car I've done around 20 trackdays. I have a funny feeling that I'm going to have a rebuild on a yearly basis with one part or another of the standard gearbox going bang. My car is the standard 260. From what I can gather though ( after asking Lotus themselves sometime ago as I was thinking of upping the power) its not to do with oil temps. I cant remember what was actually said though. i think it was Rowland that I spoke to but am not sure. I will try them again now that it has actually failed in a major way. gearbox will be out hopefully sometime in the coming week or next, but am pretty sure its going to need the 3rd & 4th gears at least. Cheers

Amer

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Whilst true about the gear temps they are generally way over the spec for the oil but cooling it help with the bigger gears however the gearbox itself is fundamentally not up to serious work without a lot of tlc.

The same problem has been around for celiac owners and the only other option is the e153. Not cheap but monkey wrench do a kit for 5k usd.

Failing that you can go for the sadev sequential at circa 20k gbp

[Mikie711]

My gearbox has developed a fault, sticking in first gear, this on a car with 1100 miles and 2 trackdays under it's belt. Always knew that the box would one day give up the ghost but thought it would take longer than 7 weeks

[alatif]

I wouldnt worry too much about it sticking in 1st. mines done it for ages in 1st and 2nd. I have to give it a good yank to get it out. It didnt happen all the time though and it didnt seem to make it worse after i'd been on track.

Regards Amer

[Scotty C]

I have Juba 3rd and 4th gears in my box.

I used to have the dreaded 3rd gear syncro going.

Spooky i have my gearbox out and away getting rebuilt just now, think this is my 5th or 6th rebuild

[alatif]

Scotty ,is this the first set of jubu gears or have you had to have them replaced as well and if so how long did they last and which ones did you go for, helical cut or straight or helical with grounded flanks. did you take any other precautionary measures as regards to the gearbox. What was the most common failure. I hope I dont have to have mine rebuilt that many times. If there is no sensible solution I can see myself selling the car ( with the gearbox rebuit ) and buying a xbow or atom. Any info. / advice you have would be greatly appreciated

Thanks Amer

[Mikie711]

Amer, mine is going in to get checked out. Might not be to much to worry about but on a 45k car that's 7 weeks old and not done that much I don't think it's unreasonable to expect it to change gear properly. Will see what happens once it's been looked at.

[Scotty C]

Scotty ,is this the first set of jubu gears or have you had to have them replaced as well and if so how long did they last and which ones did you go for, helical cut or straight or helical with grounded flanks. did you take any other precautionary measures as regards to the gearbox. What was the most common failure. I hope I dont have to have mine rebuilt that many times. If there is no sensible solution I can see myself selling the car ( with the gearbox rebuit ) and buying a xbow or atom. Any info. / advice you have would be greatly appreciated

Thanks Amer

Amer

Its not normally the gears that go its the syncros.

I think 2nd to 3rd is a big jump in a normal box and puts a lot of strain on the syncros.

I have raced in the last 3 races without 5th gear, fingers crossed this rebuild will last a lot longer. I have also fitted the upgraded motorsport cables, so will see if that makes a difference.

Juba gears are a good little upgrade if your box is getting rebuilt.

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Never needed 2nd gear on track as as you say the jump to 3rd is soo high and coupled with the flexibility of the supercharger any accel gain is lost by a gear changes (never mind another one in the braking zone).

The gears do fail with high power - when you see the size of them they are well underspecc'd for anything much higher than 260hp (although it'll be torque that kills them). But it also might be the synchros failing causing mismatched shifts and crunching the gears.

My view is that the high rpm limit Lotus have set is killing the boxes and specifically the synchros. Standard celica was 8400 then down to 8200 before settling at 7900 where as Lotus have 8500. Given that we're dealing with cars that live on track then they will be at a minimum of 6k with a more likely 7k min limit and living in the 7-8.5k band. The input shaft of the gearbox will be spinning very very fast and I suspect it's operating outside it's design limit/standard parameters.

This fits with what Walshy has found with standard NA cars in that he's broken lots of boxes even though down on power and torque.

So we're back to the same point - I really don't think the box is up to track work and even with uprated 3rd/4th gears and oil cooling they still go pop far to quickly.

It might be an idea to look at dog engagement as this would obviously eliminate the synchro issue and make for a fun track experience but a right royal pita to learn if you are used to synchros. Also I would suspect that some race regs would not allow such a change.

[Scotty C]

the way forward?

http://www.lir-racing.com/catalog/product_info.php?cPath=75_420_481&products_id=574&osCsid=ad12dcafd0a68403821883669a089e59

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But then you're replacing a probable new gearbox in a few thousand miles with a definate rebuild every 3k miles (or there abouts)

[Scotty C]

But then you're replacing a probable new gearbox in a few thousand miles with a definate rebuild every 3k miles (or there abouts)

but could be worth a second or 2

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Yes granted...

However I do believe sometimes you get what you pay for... A sequential box for what? £5k? That just doesn't fit with the mo-jo.

A decent race proven box will be up near the Sadev price.. however one at 1/3 the price... well... hmm..

Could be wrong but it just doesn't "feel" right.

[alatif]

Mike 711 - let me know what they find as im sure whats causing yours to stick is probably the same cause on mine, or was i should say. Took car to garage today so hopefully soon i should know whats failed. Thx for you thoughts Scotty and Ads

[Mikie711]

Car is now in the hands of Murray Lotus. Let you know what they find.

Edited September 14, 2010 by Mikie711

[Mikie711]

Sorry to dig up an old thread but forgot to update the progress. The oil was changed by MMC after talking with Lotus and was found to be a bit discoloured. I have since changed over to Motul gearbox oil and have experience the problem again but this time I noticed that rather than sticking in gear, which it still felt like, the car dragged forward as if I was slipping the clutch. So I am now thinking that the problem lies in a different direction and I will bleed the clutch and see if that has any effect. Problem being this doesn't happen that often and there is no set of circumstances that will induce the problem just happens at random times when crawling in traffic or pulling away.

[abrussich]

My turn to join the dead gearbox list. At the start of the last race going from 2nd to third at the drop of the green flag, third gear went away. Completely away. I've pulled the box and did see a fair amount of metal flakes in the oil so I have to assume that they are what's left of third gear. Will not know for certian untill the box is opened. For the record the car has seen three years of track play with a little over 2500 miles on the clock. Not a lot of mileage and not a good testament to the strength of the gear box.

Most likely will go with the Jubu gears for the present as a sequential is just too much cash. If the box can withstand another couple of years after the rebuild I can live with that expense versus the alternative.

The joys of racing!

[simon@scuffham.com]

This may be of interest to to you guys......

Edited September 15, 2012 by Bibs

[abrussich]

With the video being small and my eyes not what they used to be, is that a paddle shift equipped 2-11? I did not see the driver touch the stick. Nice video, thanks for posting. Would really love the chance to drive that one. One more question, how tall is the driver? I ask with regards to possible fitment of the full cage on my car.

Al B.

[simon@scuffham.com]

Yes, paddleshift, no stick to grab....

driver - that would be me then!

I'm ~5'10" although I have short legs and long body, and the seat in that car is a std road car seat so quite high (too high)