89 Vett

When I had my engine built I put a new clutch in. I replaced the 125k mile dual mass with a kit to convert it to a push style clutch that should be good up to 900ish horse power. Worked well, but there is a persistent rattle at idle when the clutch is not engaged.

Last week I shifted wrong into 3rd instead of 5th on the interstate burned the clutch bad enough that it's slipping now.

In looking at a replacement does anyone have experience with this rattle and/or preventing it? I'm not keen on a heavier flywheel.

Additionally, I'd like to accommodate some engine enhancements in 12ish months that will put me around 650 hp. Thanks in advance.

'89 ZF 6 Speed, 383 ~425 hp

bob guzzy

I did hear that the zf6 does alot of rattling on it's own, that is why I'm not concerned with the rattle in my 90.

I have a good dual mass in mine and it still rattles.

89 Vett

The "rocks/marbles in a can" sound seems common with those who have replaced their clutch. My dual mass was quiet.

rklessdriver

The dual mass FW with the additional weight has a lot more momentum which helps smooth out the firing pulses of the engine at idle... what the additional weight dosen't dampen out, the spring loaded outer/inner rings of the dual mass FW do. Hence, no gear rattle noise on a stock mostly smooth sounding idle engine....

When you convert to a single mass FW you loose alot of weight which makes the engines firing pulses hit stronger on the tranny's input shaft as it rotates causing the gear rattle you hear.

Any camshaft with some lope to it will make the gear rattle worse because of the uneven idle speed constantly jerking the input shaft as it rotates around.

My 92 dyno's just shy of 500RWHP (runs 127mph in the 1/4 mile) and I run a SPEC Stage 3 clutch with a Fidanza Alum FW.... the gear noise is quite noticeable at idle to say the least.... Just one of those things you have to deal with given the ZF tranny and a clutch/FW combo that will live at the HP I have.

Since you state that you have a push style conversion I assume it's a RAM??

I do like the idea of the RAM push style clutch conversion v/s the factory pull style which I still use.... I plan to convert once I start having problems or can no longer get parts for the SPEC pull style.

The right info sent to right tech person at RAM should be able to set you up with a new PP and disk that can take what ever power you want to put down.

Call RAM and ask to speak with Mike Norcia ....

Or you can send an email to mike@ramclutches.com
Will

89 Vett

Thanks for all the info rklessdriver, I'll give them a call tomorrow.

lt4obsesses

I have heard that ZFdoc sells a countershaft shim that eliminates the gear rattle. Found this out of course after I completed my swap, arggg. But the rattle doesn't bother me enough to pull the trans just to replace a shim.

How many miles were on the clutch? It seems odd that a 4-3 downshift would toast a clutch, unless it were old like mine was, (130K miles) or if it had notbeen fully broken in yet.

89 Vett

That's interesting... I'll reach out to him today.

I only have about 7k miles on the clutch. I wouldn't have expected it to fail either, but it's definitely slipping.

bob guzzy

My guess is the fork isn't coming back as far as it should.

Before you put the slave back on did you notice if you had any play in the fork, mine had a tiny bit maybe a 1/4".

It could be the wrong fork or the wrong pivot ball not allowing the bearing to move off the fingers, like riding the clutch all the time.

Then when you put a bunch of wear on it all at once, with that miss shift, it was just enough meat off the clutch to slip.

I feel your pain I had problems where I pulled transmissions over and over trying to find problems.

89 Vett

I didn't do the work, but from what you're suggesting the 1/4" of play would keep the clutch from engaging while mine might be snug or even 1/4" the wrong way?