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Inevitable G/Box failure..

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Just a quick entry to confirm the new 027 gearbox i fitted 2000 miles

ago has let go... It was an improvement on the earlier box and by being

considerate with high gears and full boost I thought would last at least

until I had time to upgrade... 

Unfortunately NO..!!!  After the manifold upgrade increasing the torque

to 409lb ft at 4600rpm it was way to much.. It only lasted a couple of

hundred miles and chewed up dead easy....

I will strip it out and post the details and upgrade preference in the

technical section... The aim (commitments permitting) is to complete and

test in time for the Donnington show. 14 days ?

 

 

 

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Upgrade today to remove Google ads and support TLF.

Ooooh, Just the sort of thread I am interested in as I can't upgrade my power until the gearbox is addressed.

 

Trevor.

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That's bad news and I'm surprised considering how few miles it's done. Very curious to hear what the strip down reveals.

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Don't think anyone is too surprised! What are you going to use as a replacement? We're all looking forward to the failure analysis...

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are all those crownwheels used for replacements & gearbox rebuilds still NOS?

 

  ...so what is with the material properties, and surface treatment ..think this has changed in automotive within the last 30-40 years  (as the UN1 concept and its construction-family is really old in terms of this ..we could expect this is one reason for failure -right ?!  OK, the notable increase in power is an other reason   :D  )

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Until I strip it down it is all speculation , I do not believe it will be anything 

to do with the CW&P, They are not the weak points in a well built box, 

The issue will be with the primary shaft snapping, at what position is to be

seen. My best guess is 5th gear section which is notoriously weak even

for standard power driven hard....

The fact that the gear lever and selector mechanism is jammed solid whilst

still engaged in gear but the car can be moved is a clue.. I think fifth will have

twisted off and gone behind the selector fork but be disengaged from secondary

shaft. This would fit the symptoms, however not conclusive till stripped..

As soon as it comes apart i will photo and post..  

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Much as expected. The primary shaft twisted and sheared in

the middle of the rear bearing, The result was the rear bearing 

outer race exploded.  Fifth gear cluster detached and chewed

up the rear casing and selector mechanism jamming it in position.

The stress fractures run along the primary shaft highlighting the

flex weakness when put under torque loadings outside the Box's

design specification..

Here is a few photo's..... I will cover the upgraded rebuild in the

technical section ... Any area's of particular interest you want

documenting let me know so I don't gloss over..

 

post-10519-0-70153500-1365277522.jpg

 

post-10519-0-07355900-1365277542.jpg

 

post-10519-0-52603800-1365277555.jpg

 

post-10519-0-25534500-1365277574.jpg

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Nasty!  But somehow, quite exciting...

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So your choices look like GTO or Albins in Australia.

What ratio were you running for 5th?

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Dave, bad luck mate,  but maybe time for some "changes"   Porsche  G50??

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There's a degree of schadenfreude in this...(!) Perhaps you could use the 6 speed Audi box as on Hilly's V8 conversion? Wonder what's happened to him??

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Sparky your sick......

Liking the fact that a mans shaft got so bent it broke is just sick and wrong on so many levels....!!!

You a bad bad boy...!!!

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Sparky... do we share the same therapist...!   :secret:

Because i think we need to give simon the contact details... :evil:

 

Dan 0.76 on fifth..

 

Dan, Steve, John, The choices.... As it so happens, when the extra

torque was achieved i went into overdrive looking for the most suitable

alternative ... I spent a month looking at all the options... The G50 and 

the Audi 01E were cost effective options, they needed quite a bit of fabrication

to fit onto the engine but possible...the down fall in both cases was the drive

shaft location. they were not in line and although not far out was not acceptable..

moving the engine would upset the dynamics so i binned those...

The other options were mega bucks and mainly dog boxs which did not really fit

my requirements.. So the GTO came top of the list... price is good, it will take all the

power, close ratio 1-2-3 with S/C first.. + options..  The only consideration is the tall

first which may require a bit more clutch slip....because i am running a paddle clutch

which takes the power and torque it will wear out even quicker... However after stripping 

out the clutch with 6K miles of thrash and inspecting  I was surprised and impressed.

Yes it was worn but not bad at all...the heat had soaked up the paddles perfect with no

obvious sping compression or nasties apparent...

I think i will run that specification again and see how far it will go with the tall first... :devil:

​I will order all the bits tomorrow.. £££££  :shock:  

Of cause if i had done this before braking it, I would have saved the cost of a new fifth.. :wallbash:  

Edited by CHANGES

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Hi, just curious but when you dismantled the box, what oil was in it, how much was there left and what colour?

 

edit to add, are you running an oil cooler at all?

Edited by qwerty123

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Bad news Dave,  Thanks for posting.

 

My specialist will be installing the GTO kit May 20th to 25th (into my V8).  Any items to watch for greatly appreciated.  My understanding is the bespoke bearings supplied with the kit should fit the stock casing without issue, but I have read some folks having to mod things a bit.

 

Based on my recent experience and your time line, get on the parts order quickly and specify fast delivery.  I expect the supplier is a pretty small outfit, so getting the order underway took a bit of time.  Not complaining, just the way it works for shipping overseas from a busy shop.

 

Curious, do you think you will renew the clutch parts?

 

 

Best of luck with the mod and will stay tuned.

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Until I strip it down it is all speculation , I do not believe it will be anything 

to do with the CW&P, They are not the weak points in a well built box, 

The issue will be with the primary shaft snapping, at what position is to be

seen. My best guess is 5th gear section which is notoriously weak even

for standard power driven hard....

..that is a common fault, as we all know   .my question was just pointed to Bibs comment  ;)

 

..as surface characteristics would also count for wear there on tuned up cars, as for the pressure/load on the tooth sides/flanks

 

 

-anyway , as we can see now *all as expected*     ..bad news but common, the dimensional step and the 'pressure' under the bearing cause structural damage in the shaft

 

#########

..as you ask for 'points of special interest' -if you are there on the rebuild and have some time, can you please measure up all the dimensonal interferences there on the gear-selector finger vs. shafts, what I mean is that from my impression the tolerances there between selector finger and forkshafts on the rear housing could be improved for a more 'firm' gear selection too   ..so it is not only the selector cables/joints there on the gearstick and rear cover, it is the internal layout that causes to much 'play' and some of the time delay on shifting attempts ..even if the gearbox oil heats up there

Edited by Günter

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Hi all...

I picked up the main parts late yesterday so will be starting the 

upgrade build tomorrow. 

I will do a complete documentation through the process so it can be

fully understood what the changes are, and why..

I will try cover any point and queries such as Gunter's during this.

I will post the details on this in the Technical section under The new

heading..UN1 More torque-ing points.!  

 

Dave

Edited by CHANGES

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