2.8 shaking vibration

[pl747]

I bought a 1984 S10 pickup with 2.8 carburated/700R4 stock combination. It has a constant shake/vibration at any speed. I checked the ignition wiring and it is correct and hits on all cylinders. The previous owner had the timing chain replaced and then this shaking began. Runs great, just has the shakes. I don't see anything wrong with the balancer; rubber is all good an intact and nothing broken. They said they pulled the balancer back off and tried it without the balancer and it ran exactly the same. I called O'reilleys and they said there was just one part number for ALL 2.8's. I thought maybe they got the wrong part number or something with a counter weighted timing gear. Does anyone that has been into one of these know if they had a counter weight or something that might have got installed wrong or left out? I have another identical S10 with the same combination that runs smooth that I can borrow the balancer from. The only other thing that I can think of that would give it this much shake would be the torque converter but they didn't mess with it. It would be just a coincedence that something happened to it.

[bszopi]

I would try swapping balancers since you have one available. Just because it looks good doesn't necessarily mean it is.

Welcome to the site!

[pl747]

Thanks! I see you are just over the border east of me. I think I will try that first but I'm not very optimistic. I tend to think it's internal. I'm wondering if there is some kind of counter weight that isn't part of the timing gears and chain that could have been installed wrong or even left out? If the balancer doesn't do it I guess I will have to do exploratory sugery. I wonder if anyone has a parts break down or schematic of the timing chain set and associated parts?

[CNCguy]

Perhaps the balance weight came off the flexplate (flywheel) or someone put the wrong one in. Did the PO change the engine?

[ForcedFirebird]

Perhaps the balance weight came off the flexplate (flywheel) or someone put the wrong one in. Did the PO change the engine?

X2

This is a common problem when people don't know about the early models having an externally balanced crank. If the early flexplate/flywheel was used on a late engine, or vice-versa, you will have a constant vibration througout the RPM range.

[geoffinbc]

Yup its the flexplate. Nothing else would cause a vibration that you could feel through the whole truck. DON'T run the motor any more until you resolve the issue. Take the inspection cover off and look at the back of the flex plate. For an 84, IF it is the original motor, you need to have a fairly large weight welded to the back of the flexplate. If you don't see one then you need to buy the right one. Also I have herd of cracked flywheels and flexplates causing a vibration as well. To check for that you need to drop the transmission.

[pl747]

I know the shade tree mechanic that installed the timing chain and the man that owned it too. I bought the S10 from him for $200 because of the shake after they installed the new timing chain. He said it didn't shake or vibrate before they changed it. He told me the 700R4 wouldn't shift into overdrive and it doesn't. I have several other early S10's and am building one with a 350/700R4 so I bought it mainly for parts. The one I'm building is another 1984 just like it, same blue color. I will check the counterweight on the flywheel and see if I can see anything wrong there. Would have been quite a coincidence for it to happen when they started it back up after changing the timing chain but who knows. I have another 60 degree 700R4 that works perfect and the engine runs but smokes. If I can get the vibration out of this 2.8 engine I will marry it to the other good transmission and drop it into a frame that I have and make a buggy of some sort.