I have a 93 LT-1 with 46K miles. Last summer I replaced the pressure plate, throwout bearing, pilot bearing, clutch disk, master cylinder and the slave. I did this for two reasons. One it was a little difficult to shift and the clutch pedal was very stiff. The new hydraulics and pressure plate helped both issues. However since I installed the new clutch on occasion the pedal will stiffen up and at times I'll get a groaning noise coming from the bellhousing as I depress or release the clutch pedal during the last 2" of travel (engine on or off). Last weekend I pulled the trans and bellhousing hoping to find an obvious wear problem on the throwout bearing guide tube, clutch fork or ball stud. The guide tube was is great shape if no sign of wear. The clutch fork and ball stud showed some signs of wear, but certainly not much. I took both to my local Chevy dealer and asked if they needed to be replaced. The technician said the fork was fine, but it made sense to replace the ball stub. However he said the slight wear on the stud wouldn't cause the groaning or stiff pedal. He thought it might be a defective pressure plate. I'm stumped. Does it sound like a bad pressure plate? It's an OEM Valeo pressure plate from Perfection Clutch.

I really appreciate any advice you can provide.

Thanks,

Jim

 

The one thing that you did not change was the flywheel. If you have a duel mass flywheel, that needs to be replaced also. Unfortunately you may want to also change the clutch and preasure plate.

Before you do that change check out the hydrolics.

I had a simalar problem (91 L98) and it appears that because I did not take the flywheel out the first time, then I had to go back in after about 20,000 miles of daily Chicago traffic.

 

Now that you have the clutch out, let me explain how you can check the dual mass flywheel out. With a marker, draw a line so that when you move the rearward plate of the dual mass flywheel, you can measure the distance. The idea is to hold the engine side of the flywheel stationary and move the transmission side of the flywheel in a clock wise rotation. When you can't move it any further make a mark so you can use as a measure point. Then rotate the same tranny side plate counter clock wise as far as you can and mark it. Measure the amount of rotation you can get by hand. If it is more than 1.378" the book says to replace it. Also, if there is a lot of play or looseness between the two plates, replace it. When you do replace the dual mass flywheel, make sure to match the balance weights. All this is in the Helms Manual.

 

That is some good info Strick. I too have a 92 6 spees. No problems yet.
Thanks
Jerris

 

Guys thanks for the tip. I'll check the DM movement. Could that actually increase the clutch pedal force or make a groaning noise in the bellhousing if the engines off? I guess I'm still stumped on the increased pedal force and groaning noise.

Thanks again for the thoughts,

Jim

 

I just check the movement and I'm at 1.6" max. The surface is in good shape and the primary and secondary flywheels aren't loose. Do you think I can get away without replacing it? I hate to spend the $800+ at this time.

Jim

 

jimkari,

If it turns out you need a new DM flywheel (OE, Luk), the best source/price I know of is: http://www.carolinaclutch.com/ Call Tom Haus and he'll take care of you. For an LT1 the price is about $695. Good luck to you

 

I might have a ZF Single Mass Centerforce Billet FW for sale, I wont know for sure until Centerforce calls me back with the results of their tests on my slipping Centerforce clutch, but I should know by Tuesday. If they can not pin point the clutch slipping problem, I will buy a Street Twin setup and sell my FW.

 

Guys thanks for all the good advice. I spoke with Bill over at ZFDOC.com and he said my DM should be fnie since it's close to the Helm's specs and it doesn't chatter. I think I'm going to replace the fork, ball stud and exchange the pressure plate just to be safe.

Thanks again,

Jim

 

A few thoughts:

1) A failing DM will cause a resonance, because the balancing points will no longer be located correctly. But I don't see how it will groan. I guess the masses could be accepting the load and moaning about that... ok, check.

2) If this is a street driven car, and you want to maintain drivability, I highly suggest staying with the DM. I am stunned that the DM failed so soon, tho. They are good to about 120k miles of street driving.

3) If you go SM, get the billet steel unit. It is heavier, and will absorb more of the noices and make for a better drive. It is REQUIRED that you get the SM "match balanced" to the DM, so that the engines external balance is maintained. You see, the LT1 uses the flywheel as the external balance for the rear of the engine. This balance is so very important to maintain. Any good machine shop can match balance a flywheel.

 

I thought I would do a re-post from a thread of mine.

Just in case you did not check this.

 

Thanks for all the great tips.

Jim