Need help diagnosing a clutch/tranny problem

dcdoug · #1 (**permalink**) 10-22-2012, 12:35 PM

A few weeks back, I gave drag racing a try in the cobra (first time ever). On my third launch it felt like something let go and the car lurched forward a bit and then didn't move (engine was still running fine). I was on Billboards, low RPM launch at about 2k RPM, specifically to limit the chance of breaking anything. I could back out from the starting line, but very slowly with a lot of slippage. 1st gear slipped so much that the car would only move on flat ground if I was given a push to start and overcome the inertia.

Thought for sure the pressure plate or disk had grenaded. Clutch has 5k miles on it. I don't do lots of burnouts, etc, and am probably easier on the car than many cobra drivers.

BUT, when we pulled it this weekend, the clutch looked fine. Nothing broken, condition looks good.

So what else would cause symptoms like a badly slipping clutch?

Half shafts are find. Engine runs fine.

Here's what's in it: Tranny is a TKO 600, engine is a 427FE, standard bore/stroke, never been dynoed, but probably makes ~480hp or so at the crank.

Thoughts?

GBowman · #2 (**permalink**) 10-22-2012, 01:51 PM

Not to over simplify but is there still fluid in the clutch cylinder? Sometimes we overlook the simple stuff

At least I do-its always a disaster!!!

GBowman · #3 (**permalink**) 10-22-2012, 01:52 PM

Oh and how did the first 2 passes go?

patrickt · #4 (**permalink**) 10-22-2012, 01:56 PM

Maybe the clutch packs in your limited slip.

mpanten · #5 (**permalink**) 10-22-2012, 03:58 PM

Quote:

Originally Posted by patrickt

Maybe the clutch packs in your limited slip.

That would be where I would start, It could also be the transmission.

dcdoug · #6 (**permalink**) 10-22-2012, 04:07 PM

So a bit of an update. Tested tranny and all forward gears seem to work as expected, no noises or lash issues. Maybe I should be taking a closer look at the rear end - although even if clutch packs were slipping, wouldn't I have one wheel drive regardless? I would have also thought I'd break a half shaft before trashing the limited slip, neither of which I would have expected with billboards and the sissy launches I was doing. I would have bet anything it was the clutch. Felt exactly like a slipping clutch.

Clutch pedal never got soft and if I lost hydraulics, wouldn't that mean I couldn't disengage rather than have a slipping problem? Shifting was as per normal, except that there was massive slippage. (Undriveable, had to come back on a rollback. Nice to use my AAA once in 10 years I guess....

)

Keep any add'l ideas coming.

Oh, and as to my times on the first two passes (first trips down any drag strip in any car):

12.6 @ 110
12.5 @ 111

My 60ft times were something like 2.0 if I remember right, so pretty light launches. I also wasn't concerned with reaction time.

It was fun though, I'd do it again at a low-key event like this one.

patrickt · #7 (**permalink**) 10-22-2012, 04:10 PM

Take it for an attempted drive with the tunnel off. With the "clutch slipping" badly, look back and down at the driveshaft. If it's spinning hard, then the rear needs rebuilding. ERA uses Michigan Driveline Michigan Driveline Products

FWB · #8 (**permalink**) 10-22-2012, 04:25 PM

how about any oil or coolant getting around the flywheel?

was there a chebby ahead of you with a puking powerglide?

dcdoug · #9 (**permalink**) 10-22-2012, 04:55 PM

Quote:

Originally Posted by patrickt

Take it for an attempted drive with the tunnel off. With the "clutch slipping" badly, look back and down at the driveshaft. If it's spinning hard, then the rear needs rebuilding. ERA uses Michigan Driveline Michigan Driveline Products

Unfortunately that's gonna be tough. The CSX frame and the large Lakewood bell (serious PITA to remove), combined with a few leak issues I wanted to address (changing oil pan and replacing gasket on remote filter block plus properly helicoiling a pan bolt hole), means the engine is on a stand as of yesterday.....

patrickt · #10 (**permalink**) 10-22-2012, 05:01 PM

Quote:

Originally Posted by dcdoug

Unfortunately that's gonna be tough. The CSX frame and the large Lakewood bell (serious PITA to remove), combined with a few leak issues I wanted to address (changing oil pan and replacing gasket on remote filter block plus properly helicoiling a pan bolt hole), means the engine is on a stand as of yesterday.....

Yeah... I heard.

I have absolutely no idea how you would "bench test" your limited slip. It would be interesting to know whether you had the four spider, or two spider, flavor though.

mickmate · #11 (**permalink**) 10-22-2012, 05:18 PM

Turn the pinion flange, by hand or with a couple of bolts and a bar across them.

patrickt · #12 (**permalink**) 10-22-2012, 05:21 PM

Quote:

Originally Posted by mickmate

Turn the pinion flange, by hand or with a couple of bolts and a bar across them.

Sounds good to me. Doug, you know I don't know a lot about the CSX cars, but I think they use the Dana 44 Power Lok (like ERA), which comes in two flavors: two spider gears or four spider gears. The latter is significantly stronger and is all that ERA uses. If it were me, before I put everything back in the car I would at least try Mickmate's idea and maybe even removing the differential cover and then peek inside to see if there are "chunks 'o rear" where they don't belong.

mickmate · #13 (**permalink**) 10-22-2012, 05:37 PM

Doug how did you test the tranny?

dcdoug · #14 (**permalink**) 10-22-2012, 06:07 PM

Quote:

Originally Posted by mickmate

Doug how did you test the tranny?

Not sure exactly as it was done today by one of our local club members as the car is at his house. He helped me pull the engine ("Cobra Inc", if you know Scott).

dcdoug · #15 (**permalink**) 10-23-2012, 08:10 AM

Here are some other thoughts from my local club and a bit more info:

Broken axle in the diff, left side is one thought. When the the right side tire is turned, the pinion turns, but not the left tire. Turn the left side tire and neither the pinion nor the right tire move. Does that sound normal or does this indicate the problem is in the diff?

blykins · #16 (**permalink**) 10-23-2012, 08:26 AM

I would say broken spider gears...

Generally with an open rear, you can turn one tire one way and the other tire will rotate in the opposite direction. In most positraction diffs, you can turn one tire, and the other will turn the same direction.

patrickt · #17 (**permalink**) 10-23-2012, 09:20 AM

Doug, you guys need to pull the cover and look. If your spiders went, then there's going to be some broken parts in there. If you did break your spider gears, then before you send the unit out to be rebuilt, you need to know exactly what you have. I have the manuals for both the Powr-Lok and the Trac-Lok. Both are Dana/Spicer stuff but the Powr-Lok should have four spider gears and the Trac-Lok only two. Now Tom Kirkham says there are only two spider gears in some flavors of the Powr-Lok (the crappy ones

) and I'm sure not going to second guess him on that. More likely you might have a Trac-Loc masquerading as a Powr-Lok, who knows. The point is, if you look in there and you only find two spider gears, and not four, then you need to upgrade regardless of what it is that they're calling it. Here's a diagram that will help you understand. We're talking about the "pinion mate gears" and you should have four, not two. And having the extra two spider gears is a pretty big deal.

dcdoug · #18 (**permalink**) 10-23-2012, 10:10 AM

Thanks. I may be calling to get one of them, depending on what I have (Edit - saw the post with the manuals on CACC, thanks!). Think we are going to pull the cover tonight, unless Scott does it today.