High lift camshaft,lumpy uneven idle and gearbox noise

[Monk]

Hi Guys!

I have a 1989 325iSport. Had engine modified to 2.8 using E36 328i crank
,288 degree Shrick cam was used. Car has done 1400 kms since the engine mod. She runs beautifully and a recent dyno run revealed 135KW , 237NM on the rear wheels.Plan to chip her once I have about 2k on the clock,use an E34 535i airflow meter to squeeze out a little more grunt.

My main problem is the very noisy gearbox. I'm told that this noise is due to the wild cam giving a lumpy uneven idle.With the engine shaking, the gearbox makes a noise. I'm told there is no solution , even chipping wont completely smoothen out the rough idle thus making the noise is permanent and I have to live with it!!There's no noise when the engine is cold only when @optimum operating temperature.Used a thicker gearbox oil (castrol 80W90) with no success. Apparently even overalling the gearbox wont solve the problem nor is purchasing a new gearbox!I dont want to sacrifies the power gained by going for a milder cam,say 272 degree which is a standard item in our factory South African 327iSport Evoll pushing 155KW/265NM on the flywheel(production ceased 1992!). Please Help!

[Templ8e30]

I've heard that the 6 pot getrag gearbox develops an annoying rattling sound when in neutral at idle with high mileage and lack of oil changes.

My 2.7 has a lumpy idle and I have no gearbox noise whatsoever, I'd get another gearbox that's guaranteed noise free and I'm pretty sure your problem will go away.

Cheers,

Iain T

[E30Adam]

You will never get rid of the rough idle with a 288 cam. This is one of the characteristics of the camshaft. THe lumpy idle would not cause your gearbox to make a noise.

The rattly gearbox is a totally separate issue and many getrag 260's do it. It's not something to be concerned about though, I know of people who have had their 'boxes rebuilt and still haven't eliminated the rattling.

My car does it, my mates car does it too. You just have to learn to live with it or find a rattle free gearbox.

Just out of curiosity, what are your power and torque figures in bhp and lb/ft?

[Turbo-Brown]

You should be able to lose the lumpy idle with a set of throttlebodies.

Big lift/overlap cams don't work very well with plenum systems at idle, but with a butterfly per cylinder, the lumps should become silky smooth.

Should also benefit from improved throttle response too

[Simon13]

my 325 was on 66k when i bought it and it chattered at idle, very common and nothin to worry about.

[M5pilot]

As turbo Brown says......only solution is Throttle Bodies to smooth it out.

I wouldnt go and change the cam, the gearbox noise will probably still be there.

Most E30 gearboxes make this noise and I would simply ignore it.

You try changing it for a
"guarenteed quiet one" and youll be very annoyed.

Get some throttle bodies and enjoy the extra power and smooth idle.

[buster]

mine was lumpy with the schrick cam but the e30zone chip with higher 900rpm idle sorted it out.

[hogweed]

I'm about as far from being an expert as it's possible to find on here, but... I read a Schrick article (on here I think) which said the 284/272 idled a BIT rough (but I think largely curable by raising the idle to maybe 900rpm), but that the 288 wouldn't idle smoothyl under 2000... I think...

[cabrio327i]

Ive just had the same problems with my 2.7 after fitting a 288/274 cam and found that when i took the car to get the CO emissions altered to suite the engine afer all the mods it was way out, altered this and much improved tick over and no noise, Dave

[Karan]

mine does the same...... annoying.... but hey thats life....its one of those things u have to live with. mine idles sweet at 650rpm but box rattles like a bitch, i have a mint lower mileage one to go on though....

easiest option is raising idle....