I already posted this in Transmission, but I thought I would post it here also.. This area gets more traffic, and I think some of the clutch guys here can give me a hand...
Thanks,
Jason
Original Post and pics of problem (http://www.chevelles.com/forum/ultimatebb.php/topic/28/5889.html)

Jason, see my reply to you over in the transmission section.

Tom

Checked out your reply tom, im not sure about the spring... I dont believe it was, but i did not examine it too closely when I pulled it out graemlins/angry.gif

68SS454,
I installed a TKO-600 in my 68SS as well and had issues somewhat similar. I managed to stop driving when I had a driveline balance issue. It seemed as if the driveshaft, or a ujoint was way off balance at highyway speeds.
I managed to get about 50 miles before I had the balance issue and severe clutch release problems . We as well had an issue trying to engage the clutch as if it was a TO bearing issue.
Originally we thought it may be linked to a wrong length TO bearing, or a ball stud alignment issue, or maybe the diveshaft balance.
When we tore into the issue, the input shaft was OK, but the needls and entire pilot bearing was knocked out.
To make a long story short, the input shaft of the TKO was not entering the pilot bearing far enough. It was short 50thou. Does not seem like a lot, but the input shaft did not rest on the front and back of the bearing chase, and took the needles out like now.
We put a factory brass bushing in, and it too was short, and could see that it was not going to last as well.
You like I suspected that the bellhousing was off, but ours was 100% brand new C-Force bell, fly, clutch, fork, TO etc etc. 100% new, and dialed in to within 2 thou centerline using offset dowels.
The input shaft of the TKO was perfect length as well.
Problem was my aftermarket 4340 crank. The crank flange was EXACTLY 50thou closer to the block than a stock crank. That made the input shaft 50 thou to short.
Sounds like story, how can a crank be short sticking out the back of the block. Well it was, is, and the company that makes that crank measured it in my block, and yes its short, end of story.
SOLUTION:
A longer bronze pilot bearing .250" overlength supplied by www.speedwaymotors.com (http://www.speedwaymotors.com) part # 910-25800, I purchased 3 of them, about 10 bucks a piece.
I now have in excess of 1,250 miles on the TKO-600, no issues, just tons of fun.
I hope this helps you, it cost me a lot of sleepless nights.
Hate to say this at the end, but my 68SS is a lowly little Nova, not a Chevelle.

Grandpa,....real good info there and a lot of detective work to find it. One question,....how did you find it? I mean, you can't really see the end of an input shaft as it enters the pilot bushing. Curious as to how you actually check that sort of thing. I have a scattershield and a block saver, so I know my bellhousing is sitting back a little bit from the stock position. How do I know how far in my input shaft is??

Epistuff,
To find initially if it was short, we used machine die, then a regular bronze pilot with clay.
There was no marks at all on the new TKO input shaft, however, the super T10 that we took out had the end of the input shaft blue, and the bronze pilot that was in there was very damaged, so we knew there was an issue, but thought it may have been bellhousing alignment with the old set-up.
So when we put on the new bell, fly etc., all 100% new, we dialed in the bell like I said to 2 thou with offset dowels, thinking that we were solving an existing alignment issue.
When we took a brand new needle bearing out, then the investigation started in full, finding the short crank flange issue.
A day was spent measuring the thickness of the bell, fly, inputshaft etc etc, before we figured that maybe the crank was an issue.
A stock block with stock crank was measured, and we saw our problem. But was this a single one time problem with my engine alone, no. A phone call to the crank manufacturer was made, and they did measurements in-house, and found the same issue, but with only the 509 casting 400 block.
Seems that a GM 400 casting 509 puts the crank 50 thou closer to the block. The crank manufacturer measured a 350 010, Dart block, and various GM blocks, including 400 blocks with the 511, and 817 casting, and all others were OK. Just the 509 casting places the crank closer ( Thank you GM ).
When gremlins like this appear, I would suggest getting anal with measurements, you never know what you will find.
The crank block combination if not stock with 68AA454's original post, should be checked for this same issue.

Grandpa,

That is an amazing and commendable job you did of troubleshooting and reconciling your problem! Thanks for sharing the information with the rest of us.

Thanks for the post Grandpas SS,
The engine is a 496 with a scat stroker crank, so I will definatley be checking the measurments now tongue.gif
Your post definatley piqued my interest, as 5 min after I read your post, a fellow hot rodder showed, and I told him about my problem. He said the same thing, input shaft not going fully into the pilot bushing. Needless to say, its high on my priority list now. :D