Gearbox

[Taped_Finger]

Hi,

I'm after a bit of reassurance regarding the alignment of my gearbox.

I installed the engine and gearbox over the weekend and the process went very smoothly. 

Reading the various great build blog on the internet I know that gearbox in the tunnel is cigarette paper tight but my gearbox is actually digging into the heat shield insulation and sitting on the chassis.

Is this to be excepted with the 5-speed gearbox and S3 chassis combo?

Thanks

 

 

 

[Jonathan Kay]

Is this a new build?

Are the gearbox mount and its bolts in place? 

Does the left-right positioning of the gearbox at the mount look central?

Jonathan

[Jim 123]

The touch on the heat shield is not too much to be stressed over.

Is the box actually touching the LH lower chassis longitudinal, as it's a bit hard to see for certain in your pictures?

[Taped_Finger]

It is a new build, all the bolts on the engine and gearbox mounts etc are all in position.

The gearbox does seem to be touching the chassis on the LHS and the alignment is more to the LHS side of the tunnel than central

[Tony Leigh]

My SV chassis and 5 speed box was very similar (build completed early July). I queried this with Derek Howlett at CC and he basically said there is no adjustment and that provided all mounting bolts were tight that was OK.

In the old manual it talks about adjusting gearbox left to right but that is with an old mounting plate (as I understand it). 

My car hasn’t been run very far yet as it’s due to have its IVA on Tuesday, so not sure whether there will be any ill effects when running. It has had its PBC at CC and they didn’t mention any issue with gearbox, so am assuming that Derek is correct (he has been on other queries I had).

So, in summary I think that’s just how they are.

[Taped_Finger]

Cheers Tony, I have emailed Caterham but I've not had a reply, don't know if I should take that as good news.

Hope your car passes the IVA on Tuesday

 

[Jim 123]

Don’t despair, my car had a similar tolerance build-up in the chassis, and the Mazda box is a tight clearance. First thing to try is to make yourself a wedge out of 70x70mm planed softwood, it needs to be 250mm long. Loosen the engine and all gearbox mounts.  Place the wedge down the LH side of the box with the thin end between the box and lower chassis rail.  Doing so will not harm the powdercoat.  There should be good clearance to do this in front of the gearshift aperture.  Watch you don’t damage the plastic switch housing on the side of the box while working in the area.

Use the wedge as a lever, and you can drive it downwards to max the gap between the chassis lower longitudinal and the gearbox case.  Once you have optimised the clearance in the contact area forward of the wedge, torque up all of the mounts starting with the box first.

Don’t expect much of a clearance but you should gain a few mm and all should be fine once you are on the road.

There is a further mod I can vouch for if it is needed which will give added clearance and so far has been good for the first 11,000 miles in my S3. If you think you might need this after the end of this month, PM me beforehand with your email and we can exchange contact details.

[Taped_Finger]

Cheers Jim, I'll look into the wedge solution as I do think it just needs a wee nudge to the right

[ScottR400D]

I remember a thread somewhere where a builder had a major vibration issue which turned out to be the box resting on a chassis tube. 

Seems intuitively obvious that it shouldn’t be. 

[Tazio]

Simple answer is the box should not, indeed it must not touch the chassis, the vibration through the car will be horrible! As stated loosen gearbox and engine mounts and centralise the box ( its bloody hard on your own, been there etc. ) to ensure clearance both sides.

[Taped_Finger]

Caterham came back to me saying "Your gearbox is ok, it can only fit in one position", I'll mention it at the PBC and see what is said then.

[Jim 123]

From the pre-Ikea Build Manual, page 71............ "Adjust the gearbox on its slotted mountings to achieve equal clearance within the transmission tunnel. This must be checked carefully as clearances are tight and poor alignment can cause the gearbox to contact the chassis under cornering".

As you mention you can always get things tweaked at the PBC if there is a problem once the car is on wheels.

 

[7 wonders of the world]

I'm guessing a little clearance can be gained by careful dressing of the casing in prime contact areas.

[Tony Leigh]

The advice back from CC is what they told me, so good that they are consistent. As I said in my previous post my gearbox was tight. I’m pretty sure it wasn’t touching chassis, but it is close. I hadn’t heard of Jim’s wedge idea and my gearbox mounting wasn’t slotted so no way to adjust as per pre-Ikea guidance notes.

I can see how loosening all mounting bolts may allow some movement but with my limited knowledge expect that when they are all re-torqued they will go back to pretty much where they were, unless we were expected to slot gearbox mounting plate ourselves.  So I am thinking the positioning must be dependent on chassis build / alignment which hopefully is carefully checked before being sent out. I won’t be able to check on the road until I get my car back after IVA, hopefully it doesn’t have any nasty vibrations.

[Jim 123]

Tony I think you will find that the 4 cap head nuts and nylocs that fix the gearbox mount plate to the chassis have a good degree of lateral wriggle room if you want to try. If you have any ongoing problems I can advise a simple mod to the mount that works.

As it is impossible to get a good visual, I found a reliable way of checking clearance was to cut a non crumpled slice of cardboard from the multitude of packing boxes that come with the build. If this passes comfortably along the top innermost edge of the lower chassis longitudinal without fouling on the box, you should be fine.

 

[Tony Leigh]

Thanks for advice, Jim. I’m hoping I won’t need to contact you for additional mod.

Good luck with rest of your build ‘Taped finger’.