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Fireblade gearbox rattles!
JamesMcMc - 19/10/14 at 03:20 PM

Hi,

I have an MK Indy with a 1996 Fireblade engine. At speeds of above 50mph I get loads of rattle down through the drivetrain when the car is cruising. Putting yer foot down elimates the rattle.

I have been told that some noise is to be expected at this is the dog tooths in the gearbox - but this is REALLY bad. The car drives, changes and goes into all gears, but it is really unnerving because it sounds like it's all going to go horribly wrong! Having said that I just did 200-miles in it.

The engine has only been in the car for about 600-700-miles.

Is it something that needs adjusting or something more expensive...

Cheers!

gingerprince - 19/10/14 at 04:14 PM

"They all do that, Sir". Basically when cruising at constant speed on slight throttle there's bugger all torque taking up the play in the gearbox and diff so that rattles down the prop. The solution is basically to either always have plenty throttle on or be fully off throttle, or switch off your "it sounds fooked" filter. It's a bit of a pain but you get used to it.

JamesMcMc - 19/10/14 at 04:21 PM

Thanks - I've heard that before - but mine is horrendous! Spanners in a toolbox in a washing machine! Even does it with slight throttle, only goes on hard down. I wouldn't mind a bit of noise, but this is silly. It is so loud!

mark chandler - 19/10/14 at 06:06 PM

Mine was also terrible for this initially, it's down to carb tune as the engine is shunting on overrun/cruise.

Make sure the balance is spot on, also try raising the needles, for me it needed a dynojet kit as I had a K&N filter and straight through exhaust so quite a bit different from factory.

watsonpj - 19/10/14 at 06:16 PM

Have you got a trt prop, mine was quite noisy and I changed to a trt and it improved but is still there.

gingerprince - 19/10/14 at 06:19 PM

quote:
Originally posted by watsonpj
Have you got a trt prop, mine was quite noisy and I changed to a trt and it improved but is still there.


I'm personally a little disappointed with having a TRT. For years I didn't have one, but whilst the engine was out I upgraded. Now however I tend to feel more of the movement. In the MK the engine is not in the same plane as the diff so you can't get perfect alignment and there's therefore some vibration there. With the TRT, the spinning weight is heavier so I notice it more. It's less clunky when setting off and engaging gear, but otherwise...

JamesMcMc - 19/10/14 at 10:15 PM

Balance is sport on as the dynojetting was done by Andy at AB Performance. Not sure what the prop is as I bought the car just after the engine had been put in. They told me it was the 'proper expensive prop' but it looks no different to me! Not sure how you would tell?

The only other thing I can think of is the car has some 18in wheels on - I think these are way to big, but could these be making the problem worse?

ReMan - 19/10/14 at 11:37 PM

Twheels should not be anything to do with the noise, though there a bit on the big side, but each to their own.
Howver, noisy, clattery and clonky as BEC's might be you need to get it sorted as it COULD be something serious.
Like a loose prop, failing prop joint, sprocket adaptor falling off, clutch centre failure, gearbox selector forks are all possible, just off the top of my head.
Any more clues about the noise, when it happens, all gears/speeds?

[Edited on 20/10/14 by ReMan]

JamesMcMc - 20/10/14 at 07:46 PM

No problems with prop, cv joints, etc - most deffo coming from the internals. Seems to get worse when warmed up. Does it mainly at speeds above 50 - 60mph in any gear unless accelerating (you can hear it slightly under quick deceleration).

I spoke to Andy at AB Performance (a God amongst BEC) who said he'd like to listen to it - as he isn't too far I'll take it over to him as see what the outcome is! I'll let you all know...