Jacks Transmissions Forums

Common problem with older DSM trannies. The fix used to be to upgrade to the EVOIII 5th gear which uses a bigger 5th gear synchro and is of a better design, but we think we found a solution though, and so far all that we have modified to cure this problem seem to be doing well. Soon we will make it available for all of our customers.

What is the synchro rattle issue? This is a rattling noise (almost sounds like a bad bearing) that sounds like it's coming from the trans end cover at high idle. It's harmless, but in some vehicles it can get loud enough to be annoying. A lot of people think it's the reverse synchro wave spring that does this, but it's not. What happens is when the vehicle is modified (balance shafts removed and aftermarket clutch used) more harmonic noise and torsional whip from the crank gets into the input shaft. These vibrations cause the 5th gear synchro ring to rattle in the hub and you hear the noise coming from the trans end cover. With more people using stiff sprung or solid hub clutch disks it's becoming more common.

Video of a trans on the test bench with a 5th gear synchro rattle problem:

http://www.youtube.com/watch?v=f0w49kC2Ecs

This same trans was fixed with our mod and so far it has been quiet.

Jack

Sweet. I hate explaining to people what the noise is coming from my car. I'm guessing the trans needs pulled to install this mod right?

That is correct

The fix we have now is only done when the trans is rebuilt, but if this works then I should be able to come out with another fix where all you have to do is remove the trans end cover and install a modified part to shut it up. It will be easy and simple. That won't come out until next year though probably...

Jack

Sweet I will be waiting. Just went out and started the beast to keep her happy since I have her parked. Loud ass annoying bearing noises as people walked by an looked at my car, LOL.