67 replies to this topic

[DrDomm]

Ok, I was just about 10 laps into the Last Chance 4-hour Enduro at Watkins Glen on Sunday, when my car started having this weird problem when I upshifted...most noticible from 3rd to 4th.  There seemed to be an audible hesitation after releasing the clutch pedal and applying full throttle.  It sounded as if the engine was bogging down, but then would recover.  This hestitation became progressively worse.  Watch below, please.

 

http://youtu.be/GUcPHPb8e2Y

 

I pulled into the paddock, and made sure all the wheels spun freely.  After the car cooled down for about 45 minutes, we changed spark plug wires (as that was the only think we changed prior to the race), and I went back out.  The first few laps the hesitation was brief, but then it lengthened to what is in the video.  Pulled in and packed it up.  The car is still in the trailer, as we're rearranging the garage.

 

Any thoughts on what's wrong?

 

[Jeff Wasilko]

I'd guess something in the clutch.

[DrDomm]

I'd guess something in the clutch.

 

We thought that, but I would think the engine rpm would rise, with a higher note, then come down when the clutch grabbed.  Opposite of what happened.

[Craig Berry]

Domm, I had the exact same thing at Sebring this year. We all had the same debate about the clutch and revving higher. I know Drago replaced the clutch and pressure plate....I will ask him if there was anything else....but the problem was fixed. Very frustrating and Very Slow.

[Keith Novak]

Could still be a slipping clutch.  The immediate sound after the upshift may be slightly higher than it's supposed to be but you don't notice because that part isn't too far off.  The car loses momentum and then it grabs and what you notice is the drop in RPMs because that sounds really abnormal.  If a clutch is going, 3rd to 4th is the first place you'll notice it.

[DrDomm]

Domm, I had the exact same thing at Sebring this year. We all had the same debate about the clutch and revving higher. I know Drago replaced the clutch and pressure plate....I will ask him if there was anything else....but the problem was fixed. Very frustrating and Very Slow.

 

Yeah, just kept getting slower and slower...

 

Thanks.

[Jim Drago]

Domm
We changed clutch, PP, release and pilot bearing and car was fixed. Same exact sound as yours, Craigs was notquite as bad sounding as yours, but close.

Jim

[Rob Burgoon]

Clutch.  engine isn't promptly matching the new gear speed after the clutch is dropped.  Check for an oil leak fouling your clutch disk.

[Danny Steyn]

Had the exact same sound and experience at WG at the Majors this year in my '02. Oil getting onto clutch, slipping at first and then finally mating. Worse on hills under load.

[DrDomm]

Thanks everyone.  I've got plenty of time to work on it, so we'll get it fixed for next spring.

[Jim Drago]

Domm
To Danny's point.. While you are there, go ahead and change rear main seal on engine as a precaution
Jim

[Kyle Freiheit]

Enduro track fix....... can of brake cleaner through the clutch boot.

 

 

Kyle

[DrDomm]

Enduro track fix....... can of brake cleaner through the clutch boot.

 

 

Kyle

 

Interesting.  But if oil was leaking onto it, wouldn't it continue to happen?

[RussMcB]

Enduro track fix....... can of brake cleaner through the clutch boot.

 

 

Kyle

I remember watching a pro (GTP?) race at LRP on TV years ago.  The team poured Coke or Pepsi into the clutch area to 'fix' a slipping clutch.  IIRC, it seemed to help them continue.  Pretty interesting.

[DrDomm]

Domm
We changed clutch, PP, release and pilot bearing and car was fixed. Same exact sound as yours, Craigs was notquite as bad sounding as yours, but close.

Jim

 

 

Domm
To Danny's point.. While you are there, go ahead and change rear main seal on engine as a precaution
Jim

 

Ok, finally getting around to start this project.  I'm assuming that the rear main seal is the culprit since we found a small puddle of oil under the back of the motor in the trailer.

 

I know conventional racing wisdom says, "go ahead and replace everything when you have the chance".  I just hate replacing things that aren't broken.  Along with the rear main seal, replacing the clutch disc and anything else that seems to have wear makes sense to me.  But why replace the pressure plate if it appears undamaged?  It's the priciest piece in this project.

 

But if I were to replace the pressure plate, which one?  I would assume that the ACT heavy duty one is better than stock.  Is it?  What are the differences?  And if any clutch disc is allowed, which one?  Sprung/Unsprung? 

[Jim Drago]

Domm
I use the stock pressure plate, the ACT PP feels like a diesel truck IMO. I like the feel of stock and I have never felt the need for more clamping force in our cars. It has worked well for me. I run a 3 puck unsprung disc from Clutchnet.com. They also have a sprung version. If you are easy on equipment, go with the unsprung.

Your pressure plate is probably fine, but IMO, why chance doing it twice? Keep a log and know when you changed from here forward if not doing so already.

Jim

[SaulSpeedwell]

Ok, finally getting around to start this project.  I'm assuming that the rear main seal is the culprit since we found a small puddle of oil under the back of the motor in the trailer.

 

I know conventional racing wisdom says, "go ahead and replace everything when you have the chance".  I just hate replacing things that aren't broken.  Along with the rear main seal, replacing the clutch disc and anything else that seems to have wear makes sense to me.  But why replace the pressure plate if it appears undamaged?  It's the priciest piece in this project.

 

But if I were to replace the pressure plate, which one?  I would assume that the ACT heavy duty one is better than stock.  Is it?  What are the differences?  And if any clutch disc is allowed, which one?  Sprung/Unsprung? 

 

If the labor and time are of less value to you than the cost of an all new clutch, then parts wash all the clutch parts and put it back in!  Chances are it will work fine.  I'd check the tranny front seal in addition to the engine rear main.

 

Those sintered metal pucks really WANT to grab ... if they aren't constantly being "re-oiled" by the failed seal, they WILL grab - that's precisely why it IS grabbing and pulling motor down once the oil is being slung/wiped/burned away.  Fix the leak and you've fixed the problem.

[jschwarz]

This is great!

 

I just was asking about this exact thing on mine on 3-4 shifts at RA (up hill). This was in August so it was warm and it only started 3/4 of the way through the race. The next day all was well again until about again 3/4 through the race it started slipping on 3-4 shifts again up hill. I assumed the clutch was getting too hot but was still thinking it might be worth it to replace the disk if it was glazed or something.

 

My thought is if it was oil it would do this right away right? Should be able to see how oily things are on tear down too?

[DrDomm]

Saul, thanks so much.  My plan is to get the transmission out today, and "see what's going on".  I've gone back and looked at video throughout the year, and realize that this problem was going on for a long time, but to a much lesser extent.  I would even notice/realize it while driving, but just figured it was "normal".

 

And Saul, what's your preference for type of disc/pressure plate?

[DrDomm]

This is great!

 

I just was asking about this exact thing on mine on 3-4 shifts at RA (up hill). This was in August so it was warm and it only started 3/4 of the way through the race. The next day all was well again until about again 3/4 through the race it started slipping on 3-4 shifts again up hill. I assumed the clutch was getting too hot but was still thinking it might be worth it to replace the disk if it was glazed or something.

 

My thought is if it was oil it would do this right away right? Should be able to see how oily things are on tear down too?

 

If you watch my Runoffs video, you can get an audible sense of the "delay" when shifting 3rd to 4th.  http://youtu.be/iXma17Eihjk

 

About your observations that the problem only started 3/4 thru your race, but then went away for the beginning of the next day's race...same thing happened to me at Watkins Glen.  I had the problem in the video above after about 10 laps (maybe less), and then pulled it in.  We took the car back to the paddock, had lunch, looked at a few things, and went back out.  The first couple of laps weren't that bad, but it just got progressively worse again.  I'm guessing heat has something to do with the seal's efficiency.  We then noticed some oil dripping as it went up into the trailer. 

 

I will post what I find.