Clutch and Flywheel - 1000 miles - Impala Tech
Transmission & Driveline Transmissions & Differentials

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  • 1 Post By jayoldschool
  • 1 Post By jayoldschool
  • 1 Post By Big Dave
 
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post #1 of 17 (permalink) Old 01-05-2020, 04:16 PM Thread Starter
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Shown in the attached are the clutch and flywheel out of the T-56 in my '68. I was curious to know anyone's thoughts on the condition of these parts as I'm a relative beginner in the world of the manual tramsmission. 1000 miles of easy, break-in driving. No burnouts or even hard launches as I'm still getting over sticker shock. I'm particularly interested in the dark spots on the flywheel and what that might indicate. Thanks for any replies.
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1968 Impala SS
496 Stroker
T56 Conversion
3.73 Posi-Trac
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post #2 of 17 (permalink) Old 01-05-2020, 05:29 PM
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Heat spots getting the flywheel up to 640 degrees from the disc slipping. Odd that they are all on one side of the flywheel. Those spots are now case harden and are harder (to resist wear) than the straw colored or uncolored portions of the flywheel. Additionally case hardening portions of the flywheel like that will be prone to cracking if not removed by surfacing the flywheel in a horizontal mill.

Apparently you have more engine torque than the clutch disc can hold either due to mis-adjustment or lack of clamping force. I used to run a Borg & Beck pressure plate with springs strong enough to make me walk to the left for the first half of my life, just to get enough clamping force to hold against slicks. If I were to use a clutch today with an engine I built I would use a dual disc clutch on the street or a three disc clutch if racing again.

Get the fly wheel resurfaced and start over on clutch adjustment.

Big Dave
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post #3 of 17 (permalink) Old 01-05-2020, 06:24 PM
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I have a T56 in one of my cars, I personally installed it. Your clutch disc still looks new. I think the hot spots on your pressure plate are from slipping it too much when you're taking off and perhaps between gears. With a V8/T56, you don't need any throttle input to get going, you just put it in first, and ease the clutch out, car will get going right away. Don't give it gas until you have the clutch out (and you're used to your combo). One more thing: what rear gears? You need minimum 3.42 with a T56, but 4.10s or 4.56s are a much better choice. The higher (lower numerically) gears are a killer for taking off. I had the stock 3.08s in my car for a bit before I did the 4.10s, and it was not fun.
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post #4 of 17 (permalink) Old 01-05-2020, 07:00 PM Thread Starter
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Thanks for all the replies. Rear axle ratio is 3.73. The clutch is hydraulic and I'm 99% sure it was adjusted right during the install. The fact that all the marks are on one side of the plate seems quite odd...

The dual clutch is rated at 600 ft-lbs, and the 496 is making 590 ft-lbs (on paper, have not dynoed it). Is this enough margin? I do give it gas when engaging from a stop (force of habit - a 4 banger Honda requires throttle), so maybe I'll give the no-gas method a try when she's all back together.

1968 Impala SS
496 Stroker
T56 Conversion
3.73 Posi-Trac

Last edited by 68WASAGOODYEAR; 01-05-2020 at 08:03 PM.
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post #5 of 17 (permalink) Old 01-05-2020, 08:16 PM
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Yeah, with that torque, and 3.73s, it requires NO gas until the clutch is out. Of course, you can give it gas, but just let the clutch out faster. Much faster. I know what you mean, I've driven low HP manual four bangers, too.



Have them check the flywheel to make sure it is flat (and the face is in the same plane as the hub), and maybe get a dial indicator on the crank to look for wobble run out...

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post #6 of 17 (permalink) Old 01-07-2020, 07:44 PM
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Wow - I've never seen so many heat spots before.

Definitely agree with everything Jay and Dave said already. Is that flywheel brand new or did it come with the tranny? I'm wondering if it was, umm,...not perfect from the get-go. I'd definitely get it checked, hopefully there's a good shop nearby.

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post #7 of 17 (permalink) Old 01-08-2020, 08:32 AM Thread Starter
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The flywheel was new and was part of the kit I bought from American Powertrain. I sent these pics to them and they asked if I had any oil leaks at any point that could have fouled the clutch and caused slipping. I did have an oil leak issue on the back of both heads at the valve covers...

ETA: I misquoted the torque spec for the clutch. It will handle 645 ft-lbs, so it is more than enough for the engine.

1968 Impala SS
496 Stroker
T56 Conversion
3.73 Posi-Trac

Last edited by 68WASAGOODYEAR; 01-08-2020 at 01:00 PM.
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post #8 of 17 (permalink) Old 01-08-2020, 06:49 PM
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Oil leak on a clutch is not good...
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post #9 of 17 (permalink) Old 01-10-2020, 12:52 PM
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Quote:
Originally Posted by 68WASAGOODYEAR View Post
The flywheel was new and was part of the kit I bought from American Powertrain. I sent these pics to them and they asked if I had any oil leaks at any point that could have fouled the clutch and caused slipping. I did have an oil leak issue on the back of both heads at the valve covers...

ETA: I misquoted the torque spec for the clutch. It will handle 645 ft-lbs, so it is more than enough for the engine.

Generically, I get their concern but how common is it that a valve cover leak would get to the clutch. Hell, I've had BAD valve cover leaks just last Summer/Fall and it didn't mess up my clutch. Personally, I think they are really stretching..... and I'm not buying.

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post #10 of 17 (permalink) Old 01-10-2020, 02:03 PM
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Quote:
... and I'm not buying
In their defense if you have a leaking rear main oil seal it gets sprayed all over the inside of the bell housing (slung off the flywheel), and drips down on the clutch from above. But yeah no way for a valve cover leak to affect the clutch.

Big Dave
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post #11 of 17 (permalink) Old 01-10-2020, 08:23 PM Thread Starter
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Quote:
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Quote:
... and I'm not buying
In their defense if you have a leaking rear main oil seal it gets sprayed all over the inside of the bell housing (slung off the flywheel), and drips down on the clutch from above. But yeah no way for a valve cover leak to affect the clutch.

Big Dave
I haven't seen any evidence of oil all over the inside of the bellhousing... Would it even be possible for the rear main to be leaking at 1000 miles?

1968 Impala SS
496 Stroker
T56 Conversion
3.73 Posi-Trac
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post #12 of 17 (permalink) Old 01-11-2020, 03:02 AM
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Quote:
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I haven't seen any evidence of oil all over the inside of the bellhousing... Would it even be possible for the rear main to be leaking at 1000 miles?
It is beyond possible. If not properly installed they leak from start up until it is torn down and fixed.

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post #13 of 17 (permalink) Old 01-11-2020, 09:05 PM Thread Starter
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I've looked everywhere and cannot find any evidence of an oil leak getting into the clutch. As a few of you said, it can't be from the valve covers. There is no oil anywhere on the back of the block nor anywhere inside the bellhousing, so I don't think it's the rear main seal. Dry as a bone. The only thing it could be is either the assembly lube from the ARP flywheel bolts or the anti sieze from trans input shaft, both of which were applied per the instructions.

1968 Impala SS
496 Stroker
T56 Conversion
3.73 Posi-Trac
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post #14 of 17 (permalink) Old 01-12-2020, 09:16 PM
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Do you think it's possible that the flywheel surface was ground at a slight angle?

Sent from my XT1254 using Tapatalk

HOW A NOVICE REBUILDS A 66 IMPALA CONVERTIBLE:
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post #15 of 17 (permalink) Old 01-12-2020, 10:16 PM
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Quote:
Originally Posted by BA. View Post
Do you think it's possible that the flywheel surface was ground at a slight angle?

Sent from my XT1254 using Tapatalk
Not likely. But it could be due to the clutch not being concentric to the center line of the crank. Fine spline input shafts requires a higher degree of centering the tranny than the old course ten spline Muncies. Aftermarket T56 transmissions use a 26 spline input shaft and require centering the transmission with a dial indicator and the use of adjustable pilot dowels.

If it were off center then it would wear unevenly. Which could result in all of the hot spots being on one side of the fly wheel.

Big Dave
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post #16 of 17 (permalink) Old 01-12-2020, 10:22 PM
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Great info Dave.
I would not normally expect that scenario to happen but it happened to somebody on this board recently and was verified the main. Surprised the hell out of me.

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post #17 of 17 (permalink) Old 01-13-2020, 07:57 AM Thread Starter
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Quote:
Originally Posted by Big Dave View Post
Quote:
Originally Posted by BA. View Post
Do you think it's possible that the flywheel surface was ground at a slight angle?

Sent from my XT1254 using Tapatalk
Not likely. But it could be due to the clutch not being concentric to the center line of the crank. Fine spline input shafts requires a higher degree of centering the tranny than the old course ten spline Muncies. Aftermarket T56 transmissions use a 26 spline input shaft and require centering the transmission with a dial indicator and the use of adjustable pilot dowels.

If it were off center then it would wear unevenly. Which could result in all of the hot spots being on one side of the fly wheel.

Big Dave
Despite being told by AP that the QuickTime bellhousing was toleranced tightly enough (it is priced accordingly $$$) that alignment wasn't necessary, I of course did it anyway. Three times. They were right. Each time, same result: within spec. The offset dowel pins are sitting in my tool chest.

I'll repeat this again when the bellhousing goes back on and also verify runout on the pressure plate is within spec, but I believe quite firmly that the transmission is aligned correctly.

1968 Impala SS
496 Stroker
T56 Conversion
3.73 Posi-Trac
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