6 speed transmission (new) with noise when in neutral. Is this normal?

[RandyR400]

We recently finished building our R400. We have only had it registered for about 3 weeks. We have about 400 miles on it.
It seems to be running perfectly, what a car!
I do have question to ask. Our car has the standard 6 speed transmission and makes a clatter/rattle/knocking sound when the car is HOT and idling in nuetral. When cold you need to be under the car to hear it but when hot you can hear it outside the car or when sitting in it. It is definitely in the transmission and when using a stethoscope you can hear a definite metal to metal clatter. Is there anyone with the standard 6 speed in their car that might be able to shed some light on this noise for me? I did take it to Caterham USA but came away without an answer as to whether or not this is normal.

Thanks,
Randy Cross
Colorado Springs,
Colorado

[Doug Liedblad]

I think Mopho's car does this.

I'm sure he'll be along to confirm or deny.

[mopho]

I replied to your question on the other forum as well. My 6-speed does it too and my research on blatchat described it as "The first motion shaft and laygear are dancing around a bit due to the fact that they are effectively idling with alternating accelerative and deccelerative cycles in time with the engine"
Apparently Caterham has varied the tolerances over the years and some boxes do it and others don't

[RandyR400]

That's interesting. I like the "dancing around" description. The noise is constant but random. It doesn't match the RPM of the input shaft.
I have tried two gear lubes. Redline MTL and Lucas 80/90 non synthetic. The noise seems about the same.
Any suggestion for a different lube?

[Doug Liedblad]

Red line Lightweight Shockproof.

It's what SP Components recommended for their 5 speed close ratio semi helical T9.

Also used in Hewland transaxles for F2000 and others.

I have no idea if it will help with the noise. Probably not.

[JohnCh]

Doug, have you used the LightWieght ShockProof oil in a type-9? If so, any crunching issues? When I queried Redline about oil for the Type-9 last year, I received the following response:

In the Type 9 transmissions based on the original fluid viscosity we recommend the MTL. The MT-90 or MT-85 would be options, they are compatible with composite blocker/synchro rings and wouldn’t cause excess wear. The LightWeight ShockProof wouldn’t be our recommendation, it contains a friction modifier so can be too slippery for the synchros, designed and better suited to racing and some speciality applications.

I continue to use MT-90 since it matches BGH's recommendation of a 75W90 GL4. They say anything slicker can result in crunching. Of course, they do specifically recommend against Redline products, but that's another story.

Thanks,
John

[Doug Liedblad]

Never any crunching issues. Maybe if I shift too fast but T9s aren't supposed to like that anyhow and I am careful not to bang it into gear.

I believe I tried the Redline MTL and don't recall any issues but it's been several years.

All I really know is that was what Steve Perks of SP Components told me when I called him after first installing his transmission, it might be worth another call to see if he changed his mind.

I don't know how it will work in the 6 speed.

Tell us the other story about BGH and Redline.

[JohnCh]

It's not really a story per se, just didn’t want to go off on a tangent, but since you asked

For some reason, BGH really seems to hate Redline. They've told me on a few occasions not to use it in their gearboxes as it causes premature wear, but they've never told me if they have a sufficient sample size to make that determination. My understanding is that brand isn't particularly common in the UK, so that leads me to believe they don't have a lot of data points and this was likely a situation where there was a badly worn gearbox or two and both just happened to use Redline so that was deemed the cause. Of course that's purely speculation on my part, and I could be wrong (not that it's ever happened before...). I've used Redline in my cars for years, so I’ve stuck with it in my BGH gearbox.

Regarding what they do recommend, here is a cut & paste from an email. Unfortunately I've never been able to find any of these in the US.

The Oil We recommend is Comma SX 75 W90 GL4. The oil is a Semi-Synthetic Multigrade gear oil to a GL4 spec.
This mean how slippery it is if it is too slippery I.e. GL5 the syncro doesn't properly work.
If you can't find Comma use Shell, Mobile, Silkolene, or Millers please don't use other brands.

-John

[Sean]

I also have a BGH 5-speed Type 9, and he (Brian G. Hill of BGH) told me the same. I also use Redline MT-90, because it is a semi-synthetic 75W-90 GL4 gear oil as prescribed by both my owner's manual and Mr. Hill.

Search BC if you are interested in details, but basically Mr. Hill STRONGLY recommends against (or even warns against) using Redline gear oils, while other T-9 specialists believe it to be at least satisfactory, if not straight-up recommended. From what I have read over the years, many T-9 gearboxes built/modified by BGH as well as others have used Redline gear oils for years without issue. In fact, most of the threads you will find indicate that using Redline has quieted the operation and/or smoothed out the gear changes. This is not my opinion or experience, but only what I have read.

Randy - The reason why this may be relevant to your situation is that, as I understand it, Brian Hill originally designed the 6-speed gearbox for Caterham, and it is based on the Ford Type-9 gearbox.

[RandyR400]

I read somewhere that the Caterham six speed is built with Ford internals. It would be nice to have a parts blow up of the Caterham 6 speed with corresponding Ford parts numbers.

[Roll a 7]

Mine also makes this sort of rattling noise @ idle. If I pull the shift lever towards me, whilst still in neutral, the noise abates (the lever is held between first and second gears). When I let go the noise returns. I learned to do this because the noise is obnoxious and does NOT sound like it could possibly be doing anything "good" to the car. Don't know of any other fix.

[RandyR400]

You should listen to it by placing a stethoscope (about $10 @ Harbor Frieght) against the trany case, it will scare the ---- out of you. I have heard from quite a few Caterham owners with this problem but no one can give me a concrete answer as to what is causing this. The Caterham factory said not to be to concerned about it. Somehow I think when a brand new $65k car has a transmission that sounds like one of my kids steelies ended up inside it, its OK to be concerned, and maybe a little pissed off!

[mopho]

Well I gave you a concrete answer above as per my research on blatchat

I had a brand new $130k+ Porsche GT3RS press car with a transmission that made similar noises except it was not as loud, but then again that car had a lot more sound deadening and bodywork than a Caterham ;)


The diff will make whining noises and clunks too, it's all part of what you get with what is basically a race car for the street


.

[moosetestbestanden]

I believe what Mopho said was... it's a resonant frequency thing: TADTS, mostly it seems.

The fix is not to bother w/ the six speed. While I'm sure it's a sexy sales tool due to car magazine brainwashing the reality is that the torque of the 2.0L & 2.3L engines make a 6 speed unnecessary, unless maybe there's a customer out there whose principle reason for getting a Caterham is fuel economy. Because of aerodynamic drag not even Stokes w/ his Cosworth 2.3L Atlantic motor and a Quaife sequential (which has... er... had, before it was turned to clanky rattly bits, a 1:1 6th) could pull top revs at Fontana.

A 5 speed close ratio box (w/ the long 1st gear for track junkies when necessary) is all that's needed, unless an owner likes changing gears a lot.

[mopho]

I disagree, the 6-speed is sex