73SwingerBuild
Well-Known Member
Hello all.
I've been trying to diagnose a drivetrain vibration that I've had and I think I've narrowed it down to the pinion angle. The vibration only occurs >50-55 mph and gets worse with increased speed, so I know it's not RPM dependent. I took it to a local tire shop and they test drove it and confirmed that it was definitely not a tire issue. However, they wouldn't diagnose it further because it was a "race car" (73 Dart 340 4-speed, 8-1/4" 3.55 sure-grip). I went to a driveshaft company nearby and had them balance the driveshaft and check the ujoints. He said the ujoints were good and the shaft was straight and balanced it. After having the shaft balanced, I still had the same vibration.
I bought a magnetic angle tool and checked my engine, transmission, driveshaft, and pinion angle and found the following:
- Engine (and secondary measurement on transmission): +1* up towards the rear of car
-Driveshaft: -1* down toward the rear of car
-Rear end pinion: -1* down towards rear of car
I know that having the rear pinion and driveshaft at the same angle can definitely cause a vibration. I have read a lot of forums on here and it appears that the pinion angle should match the angle of the engine. To that effect, should I purchase a set of 2* leaf spring shims to bring the rear to +1* towards the rear and should that fix my issue? I've read about "pinion angles" needing to be 3*-4* depending on application. So with the -1* driveshaft and the corrected +1* of the pinion (after I put the shims in), I'd have a 2* pinion angle. Will that be enough?
Thank you all in advance for reading. I know this is lengthy, but it's been driving me nuts and I just want to drive my car on the highway.
-Mike
I've been trying to diagnose a drivetrain vibration that I've had and I think I've narrowed it down to the pinion angle. The vibration only occurs >50-55 mph and gets worse with increased speed, so I know it's not RPM dependent. I took it to a local tire shop and they test drove it and confirmed that it was definitely not a tire issue. However, they wouldn't diagnose it further because it was a "race car" (73 Dart 340 4-speed, 8-1/4" 3.55 sure-grip). I went to a driveshaft company nearby and had them balance the driveshaft and check the ujoints. He said the ujoints were good and the shaft was straight and balanced it. After having the shaft balanced, I still had the same vibration.
I bought a magnetic angle tool and checked my engine, transmission, driveshaft, and pinion angle and found the following:
- Engine (and secondary measurement on transmission): +1* up towards the rear of car
-Driveshaft: -1* down toward the rear of car
-Rear end pinion: -1* down towards rear of car
I know that having the rear pinion and driveshaft at the same angle can definitely cause a vibration. I have read a lot of forums on here and it appears that the pinion angle should match the angle of the engine. To that effect, should I purchase a set of 2* leaf spring shims to bring the rear to +1* towards the rear and should that fix my issue? I've read about "pinion angles" needing to be 3*-4* depending on application. So with the -1* driveshaft and the corrected +1* of the pinion (after I put the shims in), I'd have a 2* pinion angle. Will that be enough?
Thank you all in advance for reading. I know this is lengthy, but it's been driving me nuts and I just want to drive my car on the highway.
-Mike