a question for CACollo (anyone else can also answer)

I was using the archives on the message board to find a problem similar to mine, and CACollo seemed to have the same vibration problem I do. Let me describe it real quick. At low engine RPM, everything is smooth. Then around 3000 to 4000 there is a really bad vibration. My rear view mirror also shakes. When the engine is in park and i rev is, there is a little roughness but not too bad. If the engine gets up alittle higher in the RPM the vibration is not as bad. What I was wondering was what CACollo found to be the problem. Could bad engine mounts cause this vibration?

 

could be the harmonic balancer. you didn't say if it is an auto. or stick shift. good luck...frank...

 

Ah yes. I guess I could have been more specific on the type of vehicle. LOL sorry Anyway it is a 1977 with the 302 v8. It is an automatic. Thanks for you time. I can use all the help I can get.

 

Hello!
Well, first of all, here is my exact problem: ('70 302 c4, all NEW!) at about 2000rpms i get a bad vibration. I have a new, correct flywheel. I notice a SLIGHT vibration at idle, but 2000 is when the mirror starts to really shake. When i shift into neutral and coast the vibration is completely gone, even though my speed remains the same (going downhill). However, if i rev it up to 2000rpms in neutral while coasting the vibration returns immediately. I have replaced the harmonic balancer, and my U-joints are all new. My vibration also goes away at about 4000rpm, but 2000 is my cruising RPM so it gets really tiring! Does this sound like your problem?

Anyways, i THINK i might have singled out my problem, and i'm going to attack over the thanksgiving holiday....
My thought is that either my torque converter could be causing it (they're nuetral balanced, but what if something became unbalanced? going to put a 2400 stall in anyways, it's 24 years old!). My other thought is that i probably didn't shim my transmission appropriately behind the front pump. My transmission rebuild kit came with thicker thrustwashers but i didn't know how to use them (skipped that section in the transmission rebuild manual!), and now i know how to use them. I am thinking that might be the real problem for my car, but until i get to it, who knows?

Have you had your tires balanced recently? How about u-joints? Harmonic balancer? One of the guys on my old post also suggested rotating the torque converter 90 degrees. Does your car keep vibrating if you shift into neutral?

Anyways, lemme know and hopefully i'll be able to help....and hopefully i'll get mine fixed this weekend!

 

With my problem, it is at a little higher rpm. Everything else seems the same though. I replaced my u-joints, but that was for another vibration. When I am going about 80-85 that is when my vibration starts in 3rd gear, which is around 3000 rpm. It also vibrates once I get up to a higher rpm between shifts. If my transmission lets it get up to its peak, the vibration stops. Of course I belive I am loosing hp with the vibration so my transmission doesnt seem to let my engine rev up that high very often.

 

LOL, i'm convinced i'm losing hp with my vibration too. I'm about out of ideas, i'll just have to let you know how my operation goes. Has your car always done it, or did it just start?

 

I did think of one other thing--the output shaft bushing on the extension housing, if worn, can cause a NASTY vibration. Mine is new, but check yours!

 

Ya my problem has pretty much always been here. The car is, I guess you could say a handmedown. No body really wanted it except me, and ever since I can remember its had this vibration. I will check the output shaft. And thanks for keeping me updated. It should help me out alot!

 

I have a 3 speed and also have nasty vibration from 2000 RPM to around 2500 or 3000 RPM then it goes away. I have new ujoints, driveshaft, new tires (balanced) etc. Where and what is this output shaft bushing (don't know anything about it - do they have them on 3 spd standard?)

 

well, i'm not so sure on a manual transmission, but on an automatic transmission the output shaft can move around a lot without the driveshaft in it. So, they use the yoke on the driveshaft to center the output shaft and put a bushing on the outside of the yoke. It's kinda hard to explain i guess, but if you take off the driveshaft and look into the transmission past the seal, you'll see a bushing that rides on the outside half of the yoke. Like an engine bearing, you'll see if it's worn (different colors/types of metal showing).

 

My dad had one worn out on his LT1 camaro, it destroyed his u-joints and ring and pinion bearings--which, by the way, is another thing that will cause a vibration.

 

A few years back the transmission on my maverick was replaced. Everything still looks fairly new however. I am hoping it will not be something in the transmission or even the output shaft because again all that stuff is only a few years old. I hate replacing things that are still fairly new on my car

 

So, not the transmission then....have you figured out if it's the engine or the car? My guess then would be that it's the differential, maybe a pinion bearing that's seen better days. I'm running low on ideas!

 

Well, I am not too sure. I didnt think it was the differential because it is rpm sensitive. However when i rev the engine in nuetral a similar vibration can be felt BUT its not anywhere near the one when its in gear.
This problem is very frustrating. I looked at my mounts and they seemed old. They are the originals, but i didnt think they would cause this vibration. I put the car in gear held the brake and nailed the gas with the hood open. The engine stayed in place so they arent broken.

 

Check the flywheel (flexplate). If it is doing this in neutral, then it is before the trans and driveshaft. Maybe the torque converter also. Check it out and let us know.

Earl