Hey on my C4, the output shaft has some up and down and side to side movement.. could this be causing the bad vibration i get at about 3500 rpm. It was hardly noticable with the 302 but i put a strong 347 in it and now it vibrates alot. Is there a bearing in the tailshaft that can be replaced or is it not that simple?
There is a Bushing that the yolk fits in, It would have to be pretty sloppy to cause vibes, but it is possible. What kind of pinion angle are you running, Anything over 4 degrees makes mine really viberate. I have also found when my joints get worn there will be some viberation. If i run the hard trans support mine seems to be more prone to want to viberate, Just some ideas hope they help.
I put new u-joints and a trans mount in last year and they still seem to be in good condition. Pinion angle should still be what it came from the factory with. They guy who built my motor said he got the rotating assembly and flexplate all together as a kit, and i noticed that the flexplate was a 28oz one, so i'd assume that the rest of it is also 28oz imbalanced.. however i dont know what balancer he put on it, looks like a cheepo to me, and cant tell what balance it is. Does the tailshaft need pulled to replace that bushing?
It doesnt vibarate when free reving in neutral.. only when driving. It viberates at around 3500 rpm when driving.. shoulda clearified that earlier Engine builder said that that kit came balanced. i have confidence that the engine builder put it together right.. hes a good guy..
Driveline problems in cars the size of Mavericks and Mustangs (driveline length is the important factor here) show balance problems at 50 mph if there are any. If your vibration happens in all gears at 3500 rpm then it has to be an engine related problem. The driveline is going slower in low gear at 3500 rpm than it is in second or high gear at 3500. You can try one thing before condemning the engine as the culprit. Take the u-joint out of the rear end and turn it 1/2 turn and then reinstall it. If the vibration is still there then you need to have the engine balanced. FYI: There is always play in the output shaft of a C4 with the driveline out. It rides in a bushing that is at the rear of the main case and there has to be clearance in that bushing for oil. That clearance is magnafied when measured 18" away at the end of the output shaft. I bet there is almost no slop at all with the driveline in it. All engines come balanced - but the tolerance is way too much for a high reving engine. My bet is that the rotating and reciprocating parts need to be balanced to tighter tolerances. Does the vibration keep getting worse as you raise the rpm or does it start to get smooth again and then come back worse? NOTE: If the kit didn't include the flexplate for the C4 it didn't come balanced because it hast to be balanced with the flexplate on it - that flex plate is out of balance to make up for the out of balance in the crank assy. you could also have a hamonic balancer with 50 gram balance and a flex plate wit 25... I agree that you have a balance problem but it probably isn't in the tranny.
Yes you will need to pull the tail housing, I would by all means check the pinion angle, its not hard to do, My pinion angle is so close to viberation that if i put to much preload in my bars mine will viberate. there is a fine line street cars have to follow for max traction and streetability, Your spring may have setteled, anything that moves the suspension can affect pinion angle, it may have been close to viberation from the factory, and over the years things settle. I would look into pinion angle before i made any other moves, Besides it never hurts to know these things anyway.
I agree with this 100%. And if you didn't have vibration problems before you put this engine in, you shouldn't have them now with the same tranny and driveshaft. I believe it's in the engine. I check out that harmonic balancer and flywheel real close.
Looking at the balancer i noticed there is no signs of external balancing on it.. its just smooth round as if it was for a internal balanced motor. can the balancers look like this and still have the imbalance? eh found the imbalancing thing on the balancer, it was on the back side .. the speedometer got real noisy too after just changing engines ??
