zupmanZ28

My car shakes like crazy at low RPMs when trying to accelerate, especially in Fifth gear. Could this be the Driveshaft? Is there any way to test it to find out? its been doing it for about a month and its starting to get annoying. If it's not the driveshaft, what else could it be?

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My 1986 Z28
GM350, T-5, 3.23's, lots of go fast goodies, 4th gen Firebird interior etc...
85 IROC w/ 1364 miles!

You'll always find what you've lost in the last place you look

R.I.P Dale Earnhardt

need4speed

Shakes??? Driveshafts vibrate. They don't shake the whole car unless the are REALLY bent. I mean an obvious wobble when the rear is on jackstands. And it will start at a certain MPH and get worse fom there regardless of what rpm or gear.

What makes you think it might be the driveshaft?? They don't go out of balance. Most factory driveshafts are not high speed balanced anyway.

Sounds more like a suspension, tire or bent axle problem.


A driveshaft problem will show up as a vibration twice the engine rpm (in third)

If its tires, it will be a low frequency vibration. (Bulge in the tire, missing balance weights, mud on the inside of the rim.)

....yeah, I miss Dale too.

zupmanZ28

I dont think its tire or suspension becuase it only does it when accelerating. At a constant cruise at any speed, the car rides normal.

The driveshaft was just a thought at what it might be, i wasn't exactly sure how to tell

Any other thoughts as to what it might be? I checked the tranny and motor mounts a minute ago and they seem fine.

89BlwnRs

I think it's safe to say it's not your driveshaft. If the driveshaft was not balanced correctly it would vibrate at a certain speed regardless of whether the car was accelerating, decelerating, or cruising. In fact, it would even matter if it was in gear, as long as the driveshaft was rotating you could run into the problem.

Jason

need4speed

Are you positive you don't have an engine misfire?? It sounds like a dead hole.

Some things that are covered up by a automatic trans will stand out like a sore thumb with a manual trans.

I can't think of anything in the drivetrain that would make the car shake like that, but go away at cruise.

zupmanZ28

Now that you mention it, it very well could be a dead cylinder. two weeks ago i had the car in an engine shop cause it ws doing the same thing only about 3 times as worse, and it turned out to be because of a bent pushrod that wasn't allowing the chamber to open. Im gonna pull the plugs tonight ans see if that tells me anything, what else can i do to check?

EDIT: Im gonna start this up in tech section.

------------------
My 1986 Z28
GM350, T-5, 3.23's, lots of go fast goodies, 4th gen Firebird interior etc...
85 IROC w/ 1364 miles!

You'll always find what you've lost in the last place you look

R.I.P Dale Earnhardt

[This message has been edited by zupmanZ28 (edited April 26, 2001).]

bigvic

What you're explaining sounds very familiar to me. You said it does it at very low rpms especially in fifth gear which is overdrive. I think is has to do with your clutch or pressure plate because my truck started doing this after I put on a cheap autozone clutch and pressure plate. It only does it when I have it in the wrong gear for the speed Im at. For instance if I put it in overdrive at 40 mph and give it gas. It's like the motor is bogging down and it begins to vibrate badly, but if I downshift and give it gas it doesn't do it, or if I get up to the right speed in that gear it stops. The only thing I can think of is the pressure plate doesn't have enough holding power and the clutch is slipping. My grandad's farm truck also does this except it does it 10 times more vioently. His does it because it is a high torque diesel that has a totally worn out clutch not to mention it also has a dirty four letter word on the front grill.

Anyways that's just my oponion and experiences. Good luck in fixing the problem.

zupmanZ28

Bigvic,
you might want to check you plugs and wires. That was my problem. I recently put headers on the car, and 3 plug wires got melted to the core. Obviously that was my problem. i replaced them with some old crappy things i had lying around and the problem went away for the most part. Once i get a another good set on there i expect it to go away completely. thanks for yours and everyone elses help though!!

------------------
My 1986 Z28
GM350, T-5, 3.23's, lots of go fast goodies, 4th gen Firebird interior etc...
85 IROC w/ 1364 miles!

You'll always find what you've lost in the last place you look

R.I.P Dale Earnhardt

bigvic

You know I think Ill check it out. If that's the case it will explain my crappy gas milage Ive had lately.