79 5 spd Vibration During Acceleration
05-23-2018, 12:35 AM
#1
79 5 spd Vibration During Acceleration
Hey folks, I've noticed while driving my 79 that I get a fairly substantial vibration through the gear shift under acceleration. It doesn't start till around 3500 RPM, faintly at first but once into the 4k's it's quite noticeable. Could this be indicative of bad motor mounts?
05-23-2018, 01:48 AM
#2
Rennlist Member
What about cruise, decel..goes away when you take the pedal off the floor?
I had this "with engine speed" WOT issue once too.
It was spark jumping under the dist cap.
I had this "with engine speed" WOT issue once too.
It was spark jumping under the dist cap.
05-23-2018, 11:18 AM
#3
My distributor cap appears to have been replaced along with wires, but no idea how long ago. Did you replace your cap or simply clean the contact points?
05-23-2018, 06:11 PM
#4
Rennlist Member
My suggestion would be to check the wheel balancing. I went trough quite some challenging possibilities (and budget) and then went to the shop around the corner to check that. Cost me 30 euro's and got me a vibration free car. I lost some lead from 1 wheel.
05-23-2018, 06:17 PM
#5
Rennlist Member
Unfortunately cruise doesn't work and I can't say with confidence now if it occurred on decel. I'll need to drive the car again. I did pop the car in neutral while still at speed and rev the engine and still felt vibration so I think it must be an engine or clutch problem.
My distributor cap appears to have been replaced along with wires, but no idea how long ago. Did you replace your cap or simply clean the contact points?
My distributor cap appears to have been replaced along with wires, but no idea how long ago. Did you replace your cap or simply clean the contact points?
Cruise = just driving, not cruise control.
Replaced the cap never 'clean'
05-23-2018, 10:02 PM
#6
Check the front bearing in the torque tube to see how far towards the transmission it is.
Anything more than 15" and the drive shaft will vibrate under load and with higher RPMs.
Another way to pinpoint a possible cause is to keep the 928 stationary and slowly rev the engine in neutral and see if you get any vibrations. This way you take other subassemblies from the equation.
Good luck with the hunt!
Anything more than 15" and the drive shaft will vibrate under load and with higher RPMs.
Another way to pinpoint a possible cause is to keep the 928 stationary and slowly rev the engine in neutral and see if you get any vibrations. This way you take other subassemblies from the equation.
Good luck with the hunt!
05-24-2018, 11:49 PM
#7
Ok, had a few minutes this evening to take car out. Made a quick vid.
to answer a few questions, I have vibration on acceleration and deceleration. I also however have this vibration when the car is parked and I rev the engine. It isn't as significant however.
I'm assuming that if I can feel this when in neutral and car not moving it must be in the engine, clutch or motor mounts. Sound right?
Here is a short vid:
https://youtu.be/sgN5tiluZlU
to answer a few questions, I have vibration on acceleration and deceleration. I also however have this vibration when the car is parked and I rev the engine. It isn't as significant however.
I'm assuming that if I can feel this when in neutral and car not moving it must be in the engine, clutch or motor mounts. Sound right?
Here is a short vid:
https://youtu.be/sgN5tiluZlU
Trending Topics
05-25-2018, 12:53 PM
#8
Rennlist Member
Video is very helpful. I’d say from that maybe misfiring or crankshaft imbalance. Like others have suggested I’d check timing, ignition, compression, fuel injectors. If all that checks out I’d pull the clutch out and make sure the flywheel, intermediate and pressure plate are in correct position. Has the car always been like this or did it just start happening? If it just started, you can rule out the latter, I think
05-25-2018, 02:36 PM
#9
Video is very helpful. I’d say from that maybe misfiring or crankshaft imbalance. Like others have suggested I’d check timing, ignition, compression, fuel injectors. If all that checks out I’d pull the clutch out and make sure the flywheel, intermediate and pressure plate are in correct position. Has the car always been like this or did it just start happening? If it just started, you can rule out the latter, I think
Thanks to all for input!
05-25-2018, 04:07 PM
#10
Rennlist Member
Clutch misaligned could cause the crank imbalance, which is a possibility if it came to you this way. I’d work out and eliminate the ignition, fuel, compression first, but keep the clutch in your back pocket. All the parts in the clutch are imbalanced and have to be orientated properly when reinstalled. If not, imbalance. There are white marks on the pieces that have to be 180 deg from each other, the workshop manual explains all this. Unfortunately, if the pieces are old, the white marks can be hard to find. But, I’m sure the gurus here would be able to tell you exactly how they go. Does the car backfire? Any unburnt fuel coming out the tail pipe? Does it start easy?
05-25-2018, 06:30 PM
#12
Rennlist Member
05-26-2018, 07:30 AM
#13
Did you check the location of the torque tube front bearing?
5-speed torque tubes are prone to the front torque tube bearing moving backwards, more so than automatics.
Sometimes it's the simple things...
5-speed torque tubes are prone to the front torque tube bearing moving backwards, more so than automatics.
Sometimes it's the simple things...
05-30-2018, 01:34 AM
#14
So busy with family last weekend and I have to be in Michigan for a wedding next weekend. I haven't had a chance to get under the car and check it out. To add to my issues my Model A Ford likely lost a rod bearing last Sunday and now I have to deal with that too.
