Running in ailments

[JNC]

If you are only talking mm it's possible!

[ScottR400D]

Can't see it myself. One mount has a triangular base and a significant angle in the horizontal, the other mount angles vertically. Incorrect fitment of either would stop the other fitting at all and try to put the engine all over the place, wrong height, canted over etc.

I guess it could happen if there was too much tolerance around the various bolts holding the mounts to the engine and the chassis but, from memory of my build, they were all a pretty good fit.

 

[Jonathan Kay]

Good point about the steering column. 
Wiggle all the exhaust joints and brackets? Loosen them one at a time and see if it affects the vibration?
Ditto engine and gearbox mounts?
Take up thy stethoscope?

It's probably worth jacking up the engine a bit either before or immediately after getting the car on stands and seeing if that changes anything.

Jonathan

[Phil G]

I had a similar vibration which gave an unpleasant fuzzy feeling which made me feel quite sick. Traced the problem to a primary pipe touching the chassis (incorrectly made). This was on a new Sigma.

[John Vine]

John Vine published a list of factors but the links are broken.

Broken link now fixed.

JV

[Mucus72]

I have diagnosed the problem. I checked Primaries, steering, engine mounts and gearbox. All is perfect apart from teh gearbox. 

Basically its sitting on the left hand side (near side) on the chassis. It's mounted centrally, I don't see how I could move it further right. The only immediate option is to push the tail end of the gearbox higher with some form of spacers under the chassis mount.

I took some photos, and the best ones are here. I'd really like your thoughts, as this is the current most common gearbox so surely others may be experiencing the same problem. If they haven't owned a Caterham previously they may even think that "they all do that".

[Mucus72]

@JV - thanks for updating speedo codes. I have just updated mine to 039558 as teh 2015/55 13" Avon CR500 will be pretty much the same as the Avon ZZS of the same size.

Out of interest, my speedo was set t0 036398 which, based on how your table appears to work, would be some massive tractor tyre ;)

[SM25T]

That must be horrible with gearbox touching the chassis !

[revilla]

Glad you've found it.

From the pictures it looks at though part of the gearbox is actually sitting vertically on the top of the chassis rail rather than just touching the sides. Is that correct?

Surely there cannot be anything so unique about your car and this must have been seen before. Have you spoken to about it Caterham yet?

One other thought - once you do get it sorted it will probably have taken the powder coat off the chassis there. Might be worth getting some protective paint or treatment on it while it is still fresh as it is rather exposed to the elements down there.

[Mucus72]

yes, it's sitting vertically, in effect the chassis tube on the LHS is acting as a shelf. 

[Mucus72]

I spoke to BaT and they had not experienced this, I sent them the photos through also. I have checked the assembly guide and there are no additional spacers mentioned, although the image in the guide shows a flange that sticks out of the bottom of the box and potentially this rests on the mount. My gearbox does not have this.

I think that if I could raise the gearbox around 2-3mm then it would not be resting on the chassis...

What would be really interesting would be to see what others on the forum have done, or even see photos. 

[Mucus72]

this is the bottom of the Mazda 5 speed from the assembly guide. Note that mine is flat across the bottom and this one looks like it would rest higher up.

[nutty7]

On your pics it clearly shows grinder marks on the casing were the flange has been removed, i'm not familiar with this gearbox but would think that this is the obvious cause of chassis contact.

[Jim 123]

Marcus to lift the box off the LH chassis rail get a couple of half nuts that will allow the 2 large fixing bolts for the gearbox to pass through without touching the bore of the half nuts (I can confirm the correct half nut size when I get back tomorrow).  The half nuts will be about 7mm thick. Use these between the underside of the box and the face of the mounting plate with the fixing bolts passed through the half nuts.  You should be able to do this by jacking up the box with the large fixing bolts removed and avoid the hassle of trying to access the cap head bolts and nylocs that fix mounting plate.

I think you'll find this can prove your theory.  After a road test if you think you have a few mm too much clearance you can get a plate fabricated.  The angle change to the driveline should be comfortable.

[Mucus72]

Hi Jim, so this is great detail firstly, thank you. So you had to do exactly this on your car for the same reason? Does that make it a known issue, and your fix something that Caterham suggested, or just a hack that you have come up with?

It strikes me as odd because EVERY Mazda 5 speed installation will have exactly the same problem. Having paid a big chunk of money for the kit, I think Caterham should do something here. 

[Mucus72]

and Jim, yes please for ID on the half nut size...

[Mucus72]

The bolts are M14x40, so wondering if it would be better for me to use spacers, in effect fat washers like these: ebay linky

[Jim 123]

Having checked the link you these might not work without modification to your washers. 

You will need washers that can sit flat on the uppermost internal face of the gearbox mounting plate.  From my notes, the max space you have in this area between the chamfered internal sides of the mount plate is 25-27mm (best leave a couple of mm wiggle space to line up all the holes).  Your spacers will centralise when you slip them in.

You might want to pop out one of the gearbox mounting bolts beforehand to check as the manual could be out of date.  From my notes, I am pretty sure that, as a proof of concept, I used 14mm half nuts that allowed the gearbox mounting bolts to pass through without engaging the threads of the half nuts.  These half nuts were 22mm across flats.

[JNC]

Stop !,  let me get this straight this is a new build ? . If so what are you doing ! If it's not right get back to CC . In my opinion something is not right pls don't bodge it up get it right. seek advice from CC 

[Mucus72]

Hi JNC, yes this is a new build. I spoke to Derek at Caterham and he suggested that giving the spacers a go is the right option. The tolerances are fine here, and Caterham have not retooled to take into account the width and shape of the Mazda 5 speed. I am going to have a go with the spacers (I also have some half nuts on the way too just in case). As a final back up I have the car booked into Book a Track, who I purchased the new kit through in mid October. If I can't get to a reasonable resolution, they as a proxy for Caterham will have to.

[JNC]

Sorry Marcus, if the car was mine I would take it back ,it sounds like a right bodge up , Why is your car the odd one why isn't there a que of other cars with the same problem  ?. Some thing is not right.

[Mucus72]

So tonight I lifted the gearbox. I took the gearbox/chassis bracket off so I could remind myself of what the inner surface looked like and to play with fitting spacers. In the end I had to trim the edges off some fat washers to get a good fit. My gearbox is now about 2mm higher than it was and therefore doesn't rest on the chassis anymore. I am still bothered by the asymmetrical nature of the box. There is loads of space on the RHS and none on the LHS. Elements of the box still stick into the heat proof foam and are therefore pressing against the car, specifically against the inner transmission tunnel skin.  

I will try and find a moment for a road test tomorrow. Hopefully vibrations will be reduced. I can't see a way to move the gearbox any further to the right. The slots in the gearbox/chassis mounts run longitudinally, so no real way to push the unit to the RHS. 

[JNC]

Can the gearbox mount be turned around ? Will that make any difference 

[Mucus72]

Hi John, the mount can't be turned around. It's an asymmetric design, short side to the left. I am rather hopeful that the work I've done tonight will cure the vibration. i will report back after a test drive tomorrow. 

[JNC]

I really hope you get it sorted soon . I don't think I would be easy going, good luck