High RPM Problems...
03-11-2008, 11:49 PM
#1
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High RPM Problems... Did a recent M6 swap and changed all the hydraulics, did the drill mod, and its bled well, the clutch was pretty new, but seems like just a stock looking LS6 replacment I think. The T56 was just built (carbon fiber syncs/ blockers, steel forks, etc etc)
I have been having trouble with a dead pedal on my 4th gear shift and sometimes even my 3rd. It seems to be strictly a high rpm issue (6,000+). Now that my cam is in, the car will rip all the way to 6,500...so when I am racing, I like to carry it that high.
What happens is I will go to grab 3rd or 4th and it will just be a wall. No grind usually, it just will not let me in. I can also provoke it if the rpms linger before WOT (for instance, a roll type race where rpms may be 4500 for a few seconds before I hit it.)
Does all this sound like pressure plate/clutch related? Seems like the only thing left, considering everything else is new, and we even made the MC adjustable. Above all, my pedal feels great then all of a sudden it will act like this. Whatta ya think?
I have been having trouble with a dead pedal on my 4th gear shift and sometimes even my 3rd. It seems to be strictly a high rpm issue (6,000+). Now that my cam is in, the car will rip all the way to 6,500...so when I am racing, I like to carry it that high.
What happens is I will go to grab 3rd or 4th and it will just be a wall. No grind usually, it just will not let me in. I can also provoke it if the rpms linger before WOT (for instance, a roll type race where rpms may be 4500 for a few seconds before I hit it.)
Does all this sound like pressure plate/clutch related? Seems like the only thing left, considering everything else is new, and we even made the MC adjustable. Above all, my pedal feels great then all of a sudden it will act like this. Whatta ya think?
Last edited by LS1Silverado05; 03-12-2008 at 12:36 AM.
03-12-2008, 08:12 AM
#5
usually a combination of drill mod being needed and the clutch line suffering from exposure to the headers causing boiling.
address those 2 issues first, change fluid, make sure it's bled well then see if you can't shift at high rpm.
address those 2 issues first, change fluid, make sure it's bled well then see if you can't shift at high rpm.
03-12-2008, 09:01 AM
#6
I would try the heat wrap fix since it's next to free and doesn't require a long process, but it sounds to me like your clutch isn't holding up to the power. If it's basically a stock clutch and you're making the power you should be on that cam-only setup, I would almost guarantee that the pressure plate just can't handle the power. Try the heat wrap, but expect to upgrade your clutch soon, from personal experience with a few of these.
03-12-2008, 09:33 AM
#7
One of the first things I did when I got my m6 car was to change to dot4 and insulate the line. In stock form it's pretty close to the cat. With headers, it's within a few inches of the collector. that's why I got my headers ceramic coated. Really keeps the heat in.
with the stock clutch, it won't hold stock power, but it doesn't mean it can't shift at 6000rpm. My car always shifted fine, though the 3-4 was iffy due to the lack of drill mod with my stock hydraulics. Basically I felt there was a difference in the pedal, but not enough to block me out.
the solution is to upgrade to 01-02 hydraulics, do the drill mod, insulate the line, use Dot4 synthetic and finally have a decent clutch. Bare minimum should be the LS7 clutch.
with the stock clutch, it won't hold stock power, but it doesn't mean it can't shift at 6000rpm. My car always shifted fine, though the 3-4 was iffy due to the lack of drill mod with my stock hydraulics. Basically I felt there was a difference in the pedal, but not enough to block me out.
the solution is to upgrade to 01-02 hydraulics, do the drill mod, insulate the line, use Dot4 synthetic and finally have a decent clutch. Bare minimum should be the LS7 clutch.
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03-13-2008, 12:03 AM
#9
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I would try the heat wrap fix since it's next to free and doesn't require a long process, but it sounds to me like your clutch isn't holding up to the power. If it's basically a stock clutch and you're making the power you should be on that cam-only setup, I would almost guarantee that the pressure plate just can't handle the power. Try the heat wrap, but expect to upgrade your clutch soon, from personal experience with a few of these.
03-13-2008, 12:29 AM
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This **** is costing me races. I cant be shifting at 5,800 when my car will pull hard right up to 6,500 
But Im scared I will put in a new clutch and still have trouble. Hope something starts working better, Im starting to feel like I should have kept the A4 in there. 
But Im scared I will put in a new clutch and still have trouble. Hope something starts working better, Im starting to feel like I should have kept the A4 in there.
03-13-2008, 12:32 AM
#11
If the clutch can't handle the power, more often than not it'll simply slip under full load. If the pressure plate can't hold the power it usually comes with a catastrophic failure or will simply not have enough clamping force to keep the clutch disk from slipping. Makes no sense why if a pressure plate can't hold the power then you wouldn't be able to push in the clutch at high rpm if anything it'd be slipping like mad.
Hydraulics are usually the culprit at high rpm shifting. Still though, if you are running LS6 clutch or lower, then don't expect that clutch to handle 400HP for long.
Your sig indicates headers and headers mean clutch line closer to heat source. Makes sense that you are boiling the fluid on WOT runs. If low rpm, cruising level shifting works like butter, it's heat.
Hydraulics are usually the culprit at high rpm shifting. Still though, if you are running LS6 clutch or lower, then don't expect that clutch to handle 400HP for long.
Your sig indicates headers and headers mean clutch line closer to heat source. Makes sense that you are boiling the fluid on WOT runs. If low rpm, cruising level shifting works like butter, it's heat.
03-13-2008, 12:51 AM
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If the clutch can't handle the power, more often than not it'll simply slip under full load. If the pressure plate can't hold the power it usually comes with a catastrophic failure or will simply not have enough clamping force to keep the clutch disk from slipping. Makes no sense why if a pressure plate can't hold the power then you wouldn't be able to push in the clutch at high rpm if anything it'd be slipping like mad.
Hydraulics are usually the culprit at high rpm shifting. Still though, if you are running LS6 clutch or lower, then don't expect that clutch to handle 400HP for long.
Your sig indicates headers and headers mean clutch line closer to heat source. Makes sense that you are boiling the fluid on WOT runs. If low rpm, cruising level shifting works like butter, it's heat.
Hydraulics are usually the culprit at high rpm shifting. Still though, if you are running LS6 clutch or lower, then don't expect that clutch to handle 400HP for long.
Your sig indicates headers and headers mean clutch line closer to heat source. Makes sense that you are boiling the fluid on WOT runs. If low rpm, cruising level shifting works like butter, it's heat.
03-13-2008, 11:42 AM
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I'm having the same problem. I changed my master and slave cylinders, did the drill mod and still nothing. My car is tore apart now waiting for my LS7 clutch to arrive(supposed to be today). My old one had all sorts of heat signs on it, one spot is blue, and I mean blue. Mine never slipped though...
And I don't buy the drill mod thing fixing it. I ran all last season just fine with no issues on stock hydrolics with no drill mod. IMO the clutch just can't handle it after so much heat for so long.
And I don't buy the drill mod thing fixing it. I ran all last season just fine with no issues on stock hydrolics with no drill mod. IMO the clutch just can't handle it after so much heat for so long.
03-13-2008, 11:48 AM
#14
If you're going through the trouble to pull the tranny to replace the slave and you still have the stock clutch in the car, why not upgrade at that point? An LS7 clutch is not that expensive for a clutch that can handle the power. Even a lower stage Spec or other company (like Stage 2) will hold any cam-only setup without issue and isn't that expensive, especially if you get the stock flywheel resurfaced instead of buying a new one.
03-13-2008, 11:50 AM
#15
The stock adjustable pressure plate fingers push the slave back at high RPM's. When you try to shift, there's not enough stroke to disengage the PP from the disk. The only solution is to change to a non-adjustable PP. My stocker was fine till just under 6k. By 4th gear, I couldnt shift at all in a street race. Sometimes I couldnt get 3rd either.
03-13-2008, 11:53 AM
#16
The stock adjustable pressure plate fingers push the slave back at high RPM's. When you try to shift, there's not enough stroke to disengage the PP from the disk. The only solution is to change to a non-adjustable PP. My stocker was fine till just under 6k. By 4th gear, I couldnt shift at all in a street race. Sometimes I couldnt get 3rd either.
03-13-2008, 12:03 PM
#17
I'm running the LS7 clutch now with the power numbers in the sig. Even prior to the clutch, I had no real issues shifting at 6krpm. I've bounced off the limiter a number of times in the early days of my car.
The drill mod DOES help with high rpm shifting. What most don't realize is that at high rpm, the lack of fluid due to the quick shifts puts A LOT of stress on your syncros to make up for the fact the clutch hasn't released completely. This will be apparent when you swap the clutch out. I still have my stocker in the garage, it has blue heat spots all over the flywheel and pressure plate. If your shifts are timed correctly and your technique good along with good syncros, you will not notice the drill mod all that much, but it WILL save your clutch. After about 20 runs at the track with the stock clutch, I started to notice it slipping under WOT load in 1st and 2nd gear. When it finally affect 3rd gear, I went LS7. Season was done, had to wait till 06 before I could test it.
Even with the LS7 and a new hydraulics, it still acted weird at high rpm shifting. Once in awhile I got a grind. It wasn't until I did the drill mod that I finally had enough confidence to hit the track again. I also had the transmission rebuilt and found the syncros were still in good shape indicating I had my shifts done right. Built for 700hp now. 06 has to be a killer year for my car. The drill mod + line insualation + 01-02 hydraulics + LS7 + dot4 has stood up to 100+ passes over the summer and over 20k miles. This was with track days were temps would hit 90's and I'd do hot laps as many as 15 times in a row with drag radials and 315 wide tires. 1.9-2.2 60 fts. Not the best, but protecting the rear is a priority.
The drill mod DOES help with high rpm shifting. What most don't realize is that at high rpm, the lack of fluid due to the quick shifts puts A LOT of stress on your syncros to make up for the fact the clutch hasn't released completely. This will be apparent when you swap the clutch out. I still have my stocker in the garage, it has blue heat spots all over the flywheel and pressure plate. If your shifts are timed correctly and your technique good along with good syncros, you will not notice the drill mod all that much, but it WILL save your clutch. After about 20 runs at the track with the stock clutch, I started to notice it slipping under WOT load in 1st and 2nd gear. When it finally affect 3rd gear, I went LS7. Season was done, had to wait till 06 before I could test it.
Even with the LS7 and a new hydraulics, it still acted weird at high rpm shifting. Once in awhile I got a grind. It wasn't until I did the drill mod that I finally had enough confidence to hit the track again. I also had the transmission rebuilt and found the syncros were still in good shape indicating I had my shifts done right. Built for 700hp now. 06 has to be a killer year for my car. The drill mod + line insualation + 01-02 hydraulics + LS7 + dot4 has stood up to 100+ passes over the summer and over 20k miles. This was with track days were temps would hit 90's and I'd do hot laps as many as 15 times in a row with drag radials and 315 wide tires. 1.9-2.2 60 fts. Not the best, but protecting the rear is a priority.
03-13-2008, 12:11 PM
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I swapped out my slave cause I had it on hand and was trying to make it to the track. I was hopeful that it would work and I could still go but it didn't happen.
My flywheel and pp did have hot spots all over it. I guess I was shifting good then.
My flywheel and pp did have hot spots all over it. I guess I was shifting good then.
03-13-2008, 09:47 PM
#19
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The stock adjustable pressure plate fingers push the slave back at high RPM's. When you try to shift, there's not enough stroke to disengage the PP from the disk. The only solution is to change to a non-adjustable PP. My stocker was fine till just under 6k. By 4th gear, I couldnt shift at all in a street race. Sometimes I couldnt get 3rd either.
04-14-2008, 11:36 PM
#20
You have described what I experience to a T.
This happened with the stock tranny and stock clutch, and also now with my rebuilt T56 with cf blockers, steel shift fork etc and Spec III.
New slave was instaleld a while back - I am hoping then that my system is a good candidate for the "drill mod" and insulating the clutch line.
Any other ideas of addressing this issue?