Chevy and GMC Duramax Diesel Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
58 Posts
Discussion Starter #1
I recently installed the bully dog triple dog on my 04 lb7 6 speed. Its set on performance and when I really hammer down on it my clutch gets hard to push and only comes back half way and starts not wanting to disengauge. You slow down and pump it a few times it will go back to normal. Any ideas on whats going on.
 

·
Registered
Joined
·
35 Posts
Your Dual Mass flywheel is not liking the extra power. My first one acted like that with stock power. It causes clutch slippage. Which causes heat. Basicly it boils the fluid in the slave cylinder. This causes the hard pedal. Time for a Single mass flywheel. You can go with one or two clutch disks depending on what you want to do and how much power you want to make.
 

·
Hi, I'm Earth. Have we met?
Joined
·
3,162 Posts
Excatly, The dual mass flywheel gm used is junk. Sometimes stock but always as soon as you add extra power you will start to get the hard and sticking peddle! The explanation i got from South Bend Clutch is that under the added engine power the two plates of the flywheel will start to separate and the only way the second one can go is back. By this moving back it takes the pressure plate fingers and puts pressure on the throw out bearing. At first its just a little bit causing just the slave to hydrolock. and as it gets worse it will start to slip the clutch because so much pressure is being aplied to the pressure plate fingers that it is just like pushing the peddle in . the only real cure to the problem is a single mass flywheel (SMF) but gm also warrentys the stock one untill 100,000 miles!

Hope this helps,
Caleb
 

·
Registered
Joined
·
58 Posts
Discussion Starter #4
So this is not going to be a cheap fix. What would be the best setup and who makes the best clutches and flywheels.
 

·
Hi, I'm Earth. Have we met?
Joined
·
3,162 Posts
Depending on the power output level you want your truck to be at, South bend Clutch has a great single disk SMF for about 900 bucks Crank it up Diesel has a single disk SMF for 1600 bucks, the difference being south bends is a cast flywheel and crank it ups is a SFI Approved Billit flywheel. A double disk set up from either place will be any where from $1900.00 to about $2300 (all Billit flywheels)depending on what you want. If your not going to be doing any sled pulling or be making 450+ rwhp i would recomend a single disk setup!

Later
Caleb
 

·
Registered
Joined
·
73 Posts
Interesting. We see this in LS1/LS6 cars. We believe that is caused by the hyd. fluid boiling. Some people are doing "Drill Out Mod" which is opening up the restrictor in the slave cyn. return line.

We had also found that pumping the clutch pedal 3 or 4 times prior to a pass also helped a bit with the stock clutch.
 

·
Hi, I'm Earth. Have we met?
Joined
·
3,162 Posts
IMO i think a the fluid is a very small part of it since the smf install i will still get a slightly stiff peddal on a real long road trip, like 300 miles+. This is with Dot 4 synthetic fluid in it also. My thought on the stiff peddal after a long trip is the amout of heat generated by the throwout bearing spining all the time, and this could be causing to get to hot! Why couldent gm just use a external slave like Ford did on the ZF??????
 

·
Registered
Joined
·
13 Posts
So this is not going to be a cheap fix. What would be the best setup and who makes the best clutches and flywheels.
I run the Crankitup Dual Disc Puller with feramic discs.This is a big power, sled pulling clutch!A lot of bite and no slip!:peelout
If you don't plan on sled pulling but want to run extra power you might want to look into Crankitup's single disc.It can be upgraded to a dual disc in the future.Just my 2 cents:thumbsup
 

·
Registered
Joined
·
35 Posts
Interesting. We see this in LS1/LS6 cars. We believe that is caused by the hyd. fluid boiling. Some people are doing "Drill Out Mod" which is opening up the restrictor in the slave cyn. return line.

We had also found that pumping the clutch pedal 3 or 4 times prior to a pass also helped a bit with the stock clutch.
I have heard of that but we only have one line. The only restriction I see is the goofy [email protected] style connector.
 
1 - 9 of 9 Posts
Top