ROTW Posted November 12, 2011 Share Posted November 12, 2011 Hello all. I am thinking of buying a SBC/TH350 260Z (looks like JTR mounts) and drove it last night. It is a typical project car that has had a few owners "helping" along the way and the history is unknown. The current owner got it non-running from a body shop owner who painted it but did not drive it. The current guy mechanical minded enough to figure out that the ditributor was installed incorrectly and get it running, but not too much past that. He then put 500 miles on it during the 6 months he has owned it, I would not driven it the way it shakes for fear of damaging something else. I did not hammer it, but under load cruising at 50-60 MPH is vibrates BAD. If I let off the gas, is lessens greatly but does not dissappear by any means (lessens greatly is relative!). If I shift into neutral and coast, IT DISSAPPEARS. While in neutral coasting, if I rev the engine, some vibration comes back, but I am not sure if it is the same vibration or just normal engine vibe present in this sort of machine when revved up some or if it is related to the issue at hand. It is not nearly the intensity of what happens under load. When shifted back into gear and under cruise load BUZZZZZZZZZZZZZZZZ, the world erupts again. I thought of something like a beat u-joint, but wouldn't this be almost as bad on deceleration? Is there something wrong with the trans? Weights lost on torque converter or something really broken inside? Can mixing 350/400 flexplates & harmonic balancer parts cause this or would I have felt it the same coasting & revving the engine in neutral? What it boils down to is 1)It is HUGE what happens when shifting into neutral when cruising at 50-60 MPH and making the vibration dissappear, and 2)I really need to make some sort of diagnosis on this so that I can figure out what the car is worth (if it needs an engine or trans this is big in selling price). Thank you very much for your help & time. Link to comment Share on other sites More sharing options...
dexter72 Posted November 12, 2011 Share Posted November 12, 2011 Does the engine run rough just idling?. Or when revving?. Maybe an Ignition wire issue, can you spray the wires with water and check for arching?. If the engine does not miss when revving it, I would lean more towards the Driveshaft. Is the exhaust or something hitting or touching the underside of the car?. Link to comment Share on other sites More sharing options...
ROTW Posted November 12, 2011 Author Share Posted November 12, 2011 It runs smooth at idle, stock low HP cam, no engine miss. It really feels MUCH stronger than a part of the exhaust touching the structure, the aftermarket auto trans shifter feels like a tuning fork. Link to comment Share on other sites More sharing options...
johnc Posted November 12, 2011 Share Posted November 12, 2011 Most likely driveline alignment. http://forums.hybridz.org/index.php?showtopic=43993 Link to comment Share on other sites More sharing options...
ROTW Posted November 12, 2011 Author Share Posted November 12, 2011 "Most likely driveline alignment." Thanks for the link/tip! Assuming that is it, then what? What is sone to correct this, re-drill the holes is the floor pans for the transmission mount for left/right & shim for up down? The front of the engine/trans seems pretty well set in place with the engine mounts. Link to comment Share on other sites More sharing options...
johnc Posted November 12, 2011 Share Posted November 12, 2011 Search please. All of this has been discussed here in excruciating detail over the years. Link to comment Share on other sites More sharing options...
Miles Posted November 12, 2011 Share Posted November 12, 2011 (edited) As johnc suggested, search the Driveline forum for driveline vibration/driveline angles. In addition, note that there can be other sources of vibration that mimic driveline angle vibration. What happens if you are parked in neutral and rev the engine high? Any vibration? Try it in neutral with the clutch in and then out. Just curious. Another source of vibration are driveline parts touching the body. For example, when first built, my 240Z with SBC and T5 trans the whole car would vibrate at high RPM while driving. The vibration always started just before the shift point and got worse as RPM increased. I suspected that my driveline angles were off. Upon inspection, I discovered that the T5 Hurst shifter housing was touching the trans tunnel under load transfering engine and driveline vibration to the body. Put the car up on a lift and look for witness marks where driveline components might move and touch the body or other parts. Use a crow bar and move components around to see if they touch/rub other parts. I had to trim off about 1/4 inch of the shifter hole on the driver's side to eliminate the vibration. Since you didn't build the car, a complete inspection of driveline angles, engine/trans mounts, half-shafts, U-joints, suspension etc would be a good place to start. Edited November 12, 2011 by Miles 1 Link to comment Share on other sites More sharing options...
PalmettoZ Posted November 12, 2011 Share Posted November 12, 2011 (edited) Unfortunately, there is not much friendly advice given on this website. It would seem that with so few Z's on the road that it would not be this way, but invariably most of the time newbie's are told to "search, its all been discussed before", which to me is really rude. Normally this turns off someone who is new to the Z scene. This might be why there are so few posts anymore here compared to a couple of years ago when I first started working on my Z. I think that the main reason people post on this site is for the social experience of interaction with other people who own the same car. Otherwise what's the point of having the site? Yes, a lot of info has been discussed before, no doubt, and there is a huge collection of knowledge here with the group. So with all that said, this will probably get moved to the "tool shed". As for what you posted about your vibration, it can be any number of things, including what you mentioned about the converter being out of balance. Another possibility would be that the motor might not be balanced, or balanced to a flywheel/clutch set-up. Do you know the history on who put the motor together? Check the angle on the driveshaft by disconnecting the transmission mounts and moving it up / down or left to right. Check and see what the angle is with a magnetic bubble angle prior to disconnection and then see if lowering it makes it straighter. The straighter the driveshaft is from the transmission to the rear-end the better. Plus the more the rear end pinion points towards the transmission the better. Verify that the driveshaft is balanced as well, could be the issue. Check the half shaft joints too, if they are worn out they can vibrate too. Hope you figure it out, start checking and figure it out by process of elimination. Good luck- Edited November 12, 2011 by PalmettoZ Link to comment Share on other sites More sharing options...
jnewby Posted November 13, 2011 Share Posted November 13, 2011 I would have to agree with PalmettoZ, I visit this website all the time, and it kinda breaks my heart when the first reply is search. I never really post much, I dig through piles of old info and broken links, but the answer is usually there, if not I use Google. The faq section is also a pretty good asset. You also might want to check your diff mounts. Link to comment Share on other sites More sharing options...
NewZed Posted November 13, 2011 Share Posted November 13, 2011 (edited) Everyone up to palmetto's post gave a suggestion. johnc gave a link with good information. Miles even gave the words to put in the search box. ROTW said thank you. You should let him complain if he wants to, it's his thread. Edited November 13, 2011 by NewZed Link to comment Share on other sites More sharing options...
GOTHALOSISM Posted November 13, 2011 Share Posted November 13, 2011 I had this issue a few weeks ago thinking it was my rear hub bearings. After I did the "shake" test I found out they were ok. After further inspection I found out where my DS bolts to the rear diff had 1 missing bolt and the rest were really loose. After adding a new bolt and some lock nuts it went away completely. Link to comment Share on other sites More sharing options...
Miles Posted November 13, 2011 Share Posted November 13, 2011 If you are not up to speed on setting drive shaft angles, you could take the car to a shop that specializes in building drive shafts such as an off road shop, driveline shop or possibly a transmission shop and have them check the angles for you. The shop may be able to find and correct the angles for you by shimming the transmission and/or differential mounts as appropriate. The shop could also check drive line balance as well. It is the little details like this that make or break a build project. Link to comment Share on other sites More sharing options...
johnc Posted November 14, 2011 Share Posted November 14, 2011 Unfortunately, there is not much friendly advice given on this website. It would seem that with so few Z's on the road that it would not be this way, but invariably most of the time newbie's are told to "search, its all been discussed before", which to me is really rude. Normally this turns off someone who is new to the Z scene. This might be why there are so few posts anymore here compared to a couple of years ago when I first started working on my Z. We don't care about the number of posts on this site, just the quality of the technical content. I think that the main reason people post on this site is for the social experience of interaction with other people who own the same car. Otherwise what's the point of having the site? Huh? The main point of this site is the technical content. If you want social interaction, join Facebook. There are dozens of Z specific FB pages where you can socially interact with Z people. Here on HybridZ its about the tech. HybridZ is not a beginner's Z site. HybridZ is not a social Z site. HybridZ is not a touchy, feely make everyone who visits here feel good site. HybridZ is not like the Special Olympics where everyone gets a trophy for showing up. Its about the tech, its about performance. 1 Link to comment Share on other sites More sharing options...
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