Vintage Mustang Forums banner

1 - 18 of 18 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter #1
Evening all,


Good evening

I’ve “upgraded” some things on my 65 and I’m having some issues. New engine build a few months ago and new AOD from performance automatics.
My current hot topic is vibration. It’s very rhythmic in nature and seems most noticeable when I let off the gas and cruise after acceleration....definitely changes proportionally with speed. I was really hoping it would go away with new trans and TC, but it’s actually worse now.

It’s a 351w with
edelbrock e-street heads.
Crane cam 226 236 @ .50
Scorpion rockers.
MSD 6AL ignition with pro billit distributor.
Current 18 degree initial with 18 bushing limiter- no vac advanc

New Performance Automatics AOD “street smart” system. 2500 stall TC. Tv pressure set to 35 with spacer installed.
New prothane trans mount

Balanced aluminum driveshaft. Spicer U joints new last fall.

9 inch rear with Richmond 4.11 gear set
6 degree axle shims...attempt at mitigating the vibration with pinion angle. Had 4 degree in it previously.

Hit me with ideas.
 

·
Premium Member
Joined
·
6,062 Posts
1) does it have a rhythmic vibration at any rpm in neutral or with the rear wheels off the ground in gear?
2) have you tried flipping the driveshaft 180°?
3) is the balance of the crank damper and flywheel matched for the engine?
4) is it possibly exhaust droning or backpressure?
 

·
Registered
Joined
·
11 Posts
Discussion Starter #3
Does not do it in neutral.
Ive never tried it with the wheels off the ground.
I did flip the drive shaft 180. No change.
harmonic dampener and fly wheel weight match.
I have electric cutouts on exhaust, no change open or closed. I thought maybe exhaust resonance as well.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #8
Image- yes sir, they are good.
Paul- That makes sense. Still gotta find the source. Once it starts, it alternates about once every 2 seconds. Vibrate. Smooth. Vibrate. Smooth. Frequency increases with speed of car.
 

·
Premium Member
Joined
·
6,062 Posts
@image98 knows where I'm going. Tires or wheels out of balance or one or more bent wheels can be enough to make you eat crayons, lick the windows and mash your tater tots at arms length.
 
  • Like
Reactions: Mdarby

·
Registered
Joined
·
127 Posts
Image- yes sir, they are good.
Paul- That makes sense. Still gotta find the source. Once it starts, it alternates about once every 2 seconds. Vibrate. Smooth. Vibrate. Smooth. Frequency increases with speed of car.
I could be very wrong here, but it sounds like you are feeling the 4 stroke cycle.

Do you have poly motor mounts too?

I've felt this driving around with dad in has flathead ford.
 

·
Premium Member
Joined
·
6,062 Posts
I once had a vibration like that at a certain speed. Turned out to be my freaking torque convertor.
 

·
Registered
Joined
·
127 Posts
A friend had a vibration in his notchback 5.0 that was making him insane. Turned out to be one of the tailpipes barely rubbing the tire. Only reason we found it was that I saw how close it was to the tire as he was driving away one random day.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #16
66- they were done a few thousand miles ago and all weights are still there.

Paul- TCP motor mounts and yes they are poly bushings
 

·
Registered
Joined
·
127 Posts
Ok. So they will transmit more vibration in general. But if the vibration is cycling, then it might be related to something in the drivetrain. Which might hard to figure out. Not fun.
 

·
Premium Member
Joined
·
6,062 Posts
I like the blue crayons best.
 
1 - 18 of 18 Posts
Top