1979 Shakes when accelerating over 45mph intermittent problem

[Gary V.]

I'm a new member and wanted some help on troubleshooting an intermittent shaking on my 1979 when accelerating from 45 to 55 mph. This is a 4 speed manual transmisision car. The shaking is felt in the body more than the steering. I've rebuilt the entire front end and replaced the engine mounts and rear half shafts. The tires are new and balanced and I had the 4 wheel alignment after the suspension was finished. The front wheel bearings are new and adjusted correctly. This is intermittent and there are times when the car drives very smooth. Any thoughts would be appreciated, thank you, Gary

[Edward J.]

Re: 1979 Shakes when accelerating over 45mph intermittent problem

Gary, The first step is to dia. the problem as a driveline vibration or engine vibration, The way to do is to drive the car at the speed the vibration starts and note the exact engine RPMS. then pull the car over and place transmisson in neutral and slowly increase the RPMS to see if the vibration is there, If so then you know its a engine vibration, if not head to the driveline. I.E. driveshaft balance, u-joints on driveshaft.take a close look at the transmisson mount, rear end snubber bushings. let us know how you make out. Ed

[Gary V.]

Re: 1979 Shakes when accelerating over 45mph intermittent problem

Thank you Ed, I will try to diag. and isolate the shaking the way you suggested. I will let you know how I make out. Gary

[Guenter J.]

Re: 1979 Shakes when accelerating over 45mph intermittent problem

The steering wheel on my 74 would shake when I hit 54 to 58 mph. My mechanic found some lug nuts were loose. He tightened them and we have been fine since. Just a thought..

[Gary V.]

Re: 1979 Shakes when accelerating over 45mph intermittent problem

I was able to isolate the problem to the driveline and not the engine. The transmission mount was in bad shape and needs replacement. It is probably the only rubber piece other than body mounts that I haven't replaced on the car. After I replace this mount I will let you know, thanks for all the input, Gary

[Gary V.]

Re: 1979 Shakes when accelerating over 45mph intermittent problem

I replaced the transmission mount and it made a big difference. I will keep checking all areas of the suspension and steering and fine tune as needed.