Dynamat on Transmission Case ?

[Heylin]

Been chasing the cause of gear rattle on my Mitsi Colt, and failing a fix (car being put back together as I type), I was wondering what people think about Dynamatting the countershaft portion of the transmission case (and perhaps the firewall near it ?)....this is wear the gear rattle \ lash noise is coming from.

Rather than try to eliminate it, If I can dull it down through soundproofing then I can live with it.

Assuming I wont create any significant heat issues in gear box by dynamatting only a portion of it ?

[GDII]

I'd think it would just melt off from the heat and smell bad. Turn up your stereo?

[Heylin]

I'd think it would just melt off from the heat and smell bad. Turn up your stereo?

LOL true that , how hot would the transmission case get ??

[GDII]

Not too sure how hot a transmission gets but if people run oil coolers on them then they have the potential to get up there in temperature. Enough to disturb the Dynamat adhesive.
Is Dynamat a black bituminous product with silver foil on it? I can't remember exactly what its made from. If it is I wouldn't stick it on anything that produces heat.

[Heylin]

Not too sure how hot a transmission gets but if people run oil coolers on them then they have the potential to get up there in temperature. Enough to disturb the Dynamat adhesive.
Is Dynamat a black bituminous product with silver foil on it? I can't remember exactly what its made from. If it is I wouldn't stick it on anything that produces heat.

Butyl based rubber adhesive (Proprietary to Dynamat). Bit of reading says its rated to 149 deg C, which is way hotter than gearbox case would ever get (approx 60-80 deg c).

Also read that MLV (Mass loaded vinyl) was good as well. (Jaycar sell for $17 a roll).

Plan if still noisy is to do a couple layers of dynamat on the countershaft section of gearbox, glue MLV to the top of that, and then do the same on the firewall just behind the gearbox.

The noise itself has me stumped, as simply changing to a kevlar facing on stock disc and uprating the pressure plate shouldnt change the driveline frequency to induce that level of gear rattle (which is usually spring damper related). I had the box fully pulled down and inspected, input shaft bearing replaced, flywheel and PP balanced, + new torsion bar...so hopefully that has got me some of the way there to eliminating the gear rattle....Dynmat\MLV is a last resort option if its still there.

[GDII]

I just had a look at the spec sheets too. Might not be as bad as I thought but I still wouldn't do it myself. Is the rattle just a sound or a vibration being transmitted to the chassis producing sound in the car?
I've put in urethane engine mount inserts into the MR2 and get more engine vibration to the chassis making other things vibrate. I've got buzzing doors now but I will look at what is loose to fix that.

[Heylin]

I just had a look at the spec sheets too. Might not be as bad as I thought but I still wouldn't do it myself. Is the rattle just a sound or a vibration being transmitted to the chassis producing sound in the car?
I've put in urethane engine mount inserts into the MR2 and get more engine vibration to the chassis making other things vibrate. I've got buzzing doors now but I will look at what is loose to fix that.

Definately gear lash, you can hear the gears clicking together in the countershaft section of the box. Happens in neutral, low gears and deceleration when coming off throttle. Getrags used in Colts, Smart, Mini, BMW are sensitive \ prone to it. It did however go from terrible to bad within the first 500 kms of running the new clutch material...so perhaps it will improve more as the clutch beds in. Looking at the clutch facings, hotspots on Flywheel and PP, its got at least another 800 kms of driving before fully bedded in

[Heylin]

Well got car back, no change, looks like only option now is to sound dampen or go back to stock clutch.