Engine/Transmission (1998.5 - 2002) Strange problem with SBC CON-OFE

[icman95]

Wondering if anyone has ever heard of this freak thing:



Had a South Bend Clutch 1947 CON-OFE installed almost a year ago by a reputable installer who has done many in the past. Even put one on my buddy's truck. Loved the clutch until last week when had problems disengaging it with the clutch pedal. Adjusted my hydraulic system to compensate but only lasted a short time. Driving home one day it just failed altogether, like the master/slave cylinders weren't working. Fortunately I was near the installer's shop and limped to his parking lot. He replaced the hyd. as the pedal was soft like a brake pedal with a hole in the system. This helped with pressure, but still wasn't enough to engage the clutch. He dropped the transmission today only to find that 3 of the (I think) 8 bolts that hold the pressure plate in sheared off at the bolt heads. This caused part of the pressure plate to be raised and engaged and the other side that was still bolted properly to remain down or disengaged. Except for metal failure of the bolts, we can't really think of what might cause this. My motor isn't modded enough to make the clutch fail. It's rated at 900 ftlbs and I'd have to say I'm not even close.



Tried calling SBC, but by the time I got to the guy's shop to take a look, they were closed. Will call in the morning. Kinda a freak thing but maybe one of you has heard of it before. Before anyone asks, the clutch has about 11K miles on it and I'm a professional truck driver so the clutch is neither old or abused.



Thanks.

 

[Arkansas Traveler]

Ken,

Sounds like you found the problem. I appreciate if you let us know how the fix works out. I just put on of those clutches in my truck a few weeks back. So far I am very satisfied with it.

Glenn

 

[icman95]

Glenn,



I'll let you know what I find out by talking to SBC tomorrow. I'm kinda hoping they'll warranty it. Can't imagine that there was anything I could have done to it to void a warranty. Up until now I have loved every minute of owning that clutch. I got it because the factory one was no good to tow my camper. Despite the factory tow ratings, the stock clutch is at its limits when towing a heavy-though not overweight-trailer. I'm guessing that my current situation is just a freak thing and some new parts will get me back on the road.

 

[GCroyle]

Just my . 02$ worth, I have not seen the parts or have anything further than the posted information.



The correct bolt for this application is a 5/16" Grade 8 piloted shoulder bolt, flanged head. The attached picture is from the same style bolt but this one is from a Ford application. The torque spec is 23 Lb/ft.



If these bolts were tightened excessively, well 23 lb/ft ain't that much pull on a 3/8" drive ratchet, but it could easily be twisted hard enough to fail if an impact gun was used.



All Dodge 5. 9L NV4500 and NV5600 use these bolts and the Ford 7. 3L series use a slightly longer pilot and OAL version.



I have no idea why it took a year to fail. The other possibility might be that it was loose from the start, got pictures?

 

[Arkansas Traveler]

Gary, What you said is why I have some concern. My SBC instructions said 20 ft lbs on the pressure plate to flywheel bolts. At 20 I still had a gap so went to 25 ft lbs. Still a small gap so on to 30 before the pressure plate seated to the flywheel. I did snug 'er down evenly alternating the bolt pattern but had some concern that the bolts were "going soft" by the time I was done. Glenn

 

[GCroyle]

Glenn,



I don't know what grade bolts you used or what size and type, but sometimes it's worthwhile to take and check them into the F/W to make sure they go down far enough to seat without thread interference in the F/W.



Were they the original style shoulder bolts?



Was the F/W significantly resurfaced and the pilot hole depth was reduced creating a bolt that got tight in the pilot prior to pulling the cover down correctly?



Good luck.

 

[Arkansas Traveler]

Gary, Clutch was a complete kit with a new flywheel, bearing, bolts, etc. I didn't think to look at the bolt head to see what grade they were since they came with the clutch. I am a little bit of a perfectionist and am kinda interested in what caused Ken's problem for future reference. The clutch I put in is functioning just fine and I would not hesitate to buy one again. Glenn

 

[GCroyle]

Glenn,



Just a follow up, the shoulder bolts are used to transfer or create the balance reference point from the F/W to the cover stamping. Ever notice that the 2nd Gen and 3rd Gen clutch covers have 2 small bolt holes in the cover and the rest are a 5/16" clearance hole. The small holes are the balance reference points and the larger holes are to bolt it down.



Now to confuse this a bit more and get slightly off topic the 1st Gen cast iron covers used a raised step on the F/W to center the cover with and a lot of pass car clutches use a dowel pin system to transfer the balance. The edge location is no longer common, piloted bolts or dowel pins are the current system.

 

[icman95]

Gentlemen,



Here's the scoop:

The guy who did the install did torque them to 20 lbs. He told me before I even asked as this is standard procedure for all the SBC clutches he installs. Like Glenn, I had everything new at the time, including the F/W and the bolts that came with it. I don't have pics as I ran right over to his shop straight from work yesterday to take a look and the camera was at home. Here's where it gets good-



I called Pete at SBC today and after explaning the problem his first inclination was also wrong torque on those bolts. I told him about the 20 lbs torque spec the mechanic used and he said that's right- 15-20lbs. Like you, Gary, he was confused as to why it took so long to fail. He said if it was a wrong torque issue it should have failed much sooner. Anyway, without an arguement or me having to ask, Pete took note of what replacement parts I needed and told me he'd ship them out at no charge to me. All I do is pay for the shipping. WHAT GREAT CUSTOMER SERVICE!! I at least expected to go back and forth between Pete and the installer about the torque stuff, but nothing. Not one bit of doubt from Pete. It was and is a pleasure to do business with SBC and I will continue to do so. I will also recommend them to anyone who is willing to listen. In the end, it was probably just a fluke, freaky break. There really will be no definite answer to the question, but I'll be back on the road soon thanks to Pete.



If I get a chance to photo the parts before the shop throws them away I'll post them here, but I'm not sure I'll get the chance.



Thanks everyone for your input.