downshifting engagment. Any ACT 2900 guys?

[assault187]

I had installed a ACT 2600 kit with a street disc and lightweight flywheel a little while back but from the power the car was putting down the clutch slipped 3rd and 4th gear. I recently stepped up to the ACT 2900 with the street disc and new lightweight flywheel (I hate down time for somthing simple) All was installed and broken in properly but when downshifting, its a must to rev match for smooth downshifts. When not rev-matching (especially into 2nd gear from 3rd) the shake is violent when the clutch is engaging. Besides that all is well. Im sure its because it grabs soo hard but has anyone experienced the same problem?

 

[bmoha2]

I wonder if poly motor mounts would decrease that shake or if it would in fact intensify it?

 

[assault187]

The trans mount and main motor mount are solid polyurathane mounts. the front and back are polyurathane inserts....

 

[kahl23]

I believe stiffer mounts would intensify the engagement lurch when downshifting without perfectly rev-matching. From my thinking, the engine torques because the differential between the drivetrain speed and motor speed has to be equalized. When you have softer mounts that torque is absorbed more by the flex in the soft rubber, instead of being transferred to the chassis like it would be with stiffer mounts. A faster/harder engaging clutch would make the lurching more intense i believe, as there is less give in the clutch to equalize the different speeds.

 

[Defiant]

When not rev-matching (especially into 2nd gear from 3rd) the shake is violent when the clutch is engaging. Besides that all is well. Im sure its because it grabs soo hard but has anyone experienced the same problem?

Well, yeah, that's a manual transmission. And this is why DSMs all have blown 2nd gear synchros.

Double-clutch. Things will last forever. But at least double-kick ("rev-match").

 

[assault187]

Double clutching does nothing, it still stumbles/shakes violently when downshifting to 2nd or 3rd. Getting it in gear is no problem, the trans is fully built and never grinds. I wanna say its only because the clutch grabs so hard but I can't find somone with a simalar setup or problem so I dont know....

 

[kahl23]

That really doesn't make sense, if you double clutch correctly on a working transmission, there should be no shake or anything, it should be a smooth engagement. Technically speaking, it's possible to smoothly downshift without the clutch, provided you're able to rev match correctly, rally drivers did it before the days of high dollar sequential transmissions (and i suppose some still do). Are you sure your synchros are still alive? or that you're rev matching correctly?

 

[assault187]

yes my syncros are still alive and kicking. The problem only exists when the clutch is grabbing the flywheel so how do you figure double clutching will work? This is not a syncro issue with the trans, there is no grinding and it slides into each gear flawlessly..... Yes I am rev matching correctly....Thats why the problem will not occur when I rev match to downshift.

 

[91talon27]

I am running a ACT 2900 with a street disk and a Fidanza Flywheel. Although I have it in a 1g I've never had any problems with shaking on downshifts. It shifts as smooth as butter both up shifting and down shifting. Are you sure that the trans is tight as if a bolt loosened up it could cause the shaking on down shifts?

 

[assault187]

I'll double check everything today, hopefully I didnt break the trans mount again.

 

[1fastlaser]

sounds like a mount is broke or loose, and maybe a warped flywheel/pressure plate

 

[kris_stewart10]

well what it is the stock clutch is made to slip to a point and that clutch there is GRABBING and pulling and its a little hard but i do it all the time and i have an act 2600 with a fidanza lightweight flywheel and mine shakes a little bit like yours from 3rd to 2nd and i just ignore it except when i rev match it the only time i do that is when my girl is in the car so i dont look like i cant drive a stick but i dont downshift until about 35-40 so it doesnt shake significantly but its not that big of a problem for me and i have a busted motor mount on the left side but if i change that i think i would be good

 

[95burgundyesi]

You are not suppost to runa street disk with a 2900. But people do it, so I think you may have a different problem.

 

[talon187]

i had a 2600 with a street disk then went with a light weight flywheel and 6 puck the street disk was fine. the 6 puck would make the car shake a tad not horrible tho and i could down shift with no issues the only thing i didnt like with the light weight flywheel is if i tossed it into netural going down a hill it would fall flat on its face and stall. i have since went with twin disk. car shifts better and eaiser and its not neraly has harash on the trans as the acts are

 

[assault187]

Everthing is tight, trans mount is in one peice. '

Quick question, Why do you guys say the ACT clutches are so harsh on the trans?

 

[talon187]

have you ever tried to shift an act clutch at 8k or even 7500? they don't like to disengage and they are hard on the syncros.

 

[1fastlaser]

its gonna shake when downshifting without rev matching. You have too plain and simple. You have a heavy pressure plate and a street disk, even if the pressure plate is alittle warped its gonna shake. I have a ptt twin disk and it has to be rev matched to downshift. If i dont it makes the most horrible squeeling, shaking ever. Its apart of the game. if the rpms are at idle, the clutch has to violently catch up to the rpm the motor is going to spin at.

Heavy pressure plates but loads on all syncros in the trans, especially if there not adjusted right and full disengaging when trying to shift. You have to check to make sure theres not any clutch drag at high rpms. If there is its not fully disengaging.

 

[talon187]

my ptt twin disk doesnt have to be rev matched to down shift...my car shifts awsome with that clutch

 

[assault187]

have you ever tried to shift an act clutch at 8k or even 7500? they don't like to disengage and they are hard on the syncros.

well, My 1-2's are impossible...past that all is well. I'll keep this in mind when searching for a new clutch


Any recomendations for the next clutch setup for 450+ hp?

its gonna shake when downshifting without rev matching. You have too plain and simple. You have a heavy pressure plate and a street disk, even if the pressure plate is alittle warped its gonna shake. I have a ptt twin disk and it has to be rev matched to downshift. If i dont it makes the most horrible squeeling, shaking ever. Its apart of the game. if the rpms are at idle, the clutch has to violently catch up to the rpm the motor is going to spin at.

Heavy pressure plates but loads on all syncros in the trans, especially if there not adjusted right and full disengaging when trying to shift. You have to check to make sure theres not any clutch drag at high rpms. If there is its not fully disengaging.

Thats what I figured but I had never experienced it before, and I dont know anyone running anything stronger then a 2600 on a DSM.

 

[1fastlaser]

my ptt twin disk doesnt have to be rev matched to down shift...my car shifts awsome with that clutch

Yeah at low speeds unless your downshifting on the highway to a lower gear and the revs drop to idle then have to come back up to 4500 5k without rev matching.