# Drive belt wobble
**URL:** https://59plymouth.net/t/drive-belt-wobble/3818
**Category:** Tech Support
**Created:** [June 16, 2022, 9:01pm UTC](https://59plymouth.net/t/drive-belt-wobble/3818 "2022-06-16T21:01:10Z")
**Posts on this page:** 17
**Page:** 1
### Author:  [@vanguy16](https://59plymouth.net/u/vanguy16)
#### Post date: [June 16, 2022, 9:01pm UTC](https://59plymouth.net/t/drive-belt-wobble/3818/1 "2022-06-16T21:01:10Z")
Does anyone else see significant belt wobble on their 318’s? I’m seeing a significant wobble l from the alternator to crankshaft span.
Just wondering if it’s normal because it’s quite a long run.
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### Author:  [@Faulkner](https://59plymouth.net/u/Faulkner)
#### Post date: [June 17, 2022, 3:10am UTC](https://59plymouth.net/t/drive-belt-wobble/3818/2 "2022-06-17T03:10:22Z")
Loretta has an alternator, Mike? Not a generator?
Any chance you can take a video, and post it here? Perhaps then we can advise.
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### Author:  [@vanguy16](https://59plymouth.net/u/vanguy16)
#### Post date: [June 17, 2022, 7:57pm UTC](https://59plymouth.net/t/drive-belt-wobble/3818/3 "2022-06-17T19:57:08Z")
Hi Dan.
Yes, it’s been upgraded to an alternator. Unfortunately I’ve taken video but the vibration doesn’t show on video well at all.
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### Author:  [@vanguy16](https://59plymouth.net/u/vanguy16)
#### Post date: [June 17, 2022, 8:01pm UTC](https://59plymouth.net/t/drive-belt-wobble/3818/4 "2022-06-17T20:01:22Z")
Imagine that wobble being 20-30 times faster as the camera smooths it out so to speak.
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### Author:  [@Faulkner](https://59plymouth.net/u/Faulkner)
#### Post date: [June 17, 2022, 9:25pm UTC](https://59plymouth.net/t/drive-belt-wobble/3818/5 "2022-06-17T21:25:50Z")
Ah, I didn’t read correctly; I thought at first perhaps a pulley was wobbling. That doesn’t seem to be the case.
The crankshaft pulley is providing the pull on the belt, first the water pump & fan pulley, then the alternator pulley. Any slack in the belt will appear between the alternator and the crank pulley. Are you sure the belt is good and tight? I’ll ask Dick Koch to review this thread and comment as well.
Dan
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### Author:  [@Mark\_Merritt](https://59plymouth.net/u/Mark_Merritt)
#### Post date: [June 17, 2022, 9:30pm UTC](https://59plymouth.net/t/drive-belt-wobble/3818/6 "2022-06-17T21:30:13Z")
Looks like there is slack on the bottom side, motor turns clockwise. Does the alternator bearing spin free when off the belt? Mark
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### Author:  [@Dick\_Koch](https://59plymouth.net/u/Dick_Koch)
#### Post date: [June 17, 2022, 9:52pm UTC](https://59plymouth.net/t/drive-belt-wobble/3818/7 "2022-06-17T21:52:44Z")
Single groove pully on crankshaft. I guess no power steering. The belt is tightened correctly when you push down in the middle of a span and it moves approx. 1/2". Dan can you post the video of my engine running while driving the alternator, AC compressor and water pump.
Thanks,
Dick.
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### Author:  [@Faulkner](https://59plymouth.net/u/Faulkner)
#### Post date: [June 17, 2022, 9:56pm UTC](https://59plymouth.net/t/drive-belt-wobble/3818/8 "2022-06-17T21:56:48Z")
Sure, Dick - Mike, here’s a vid of Dick’s 318 running. You’ll note that there isn’t any play in his fan belt. Check the tightness of the belt, and failing that, confirm that the alternator isn’t hanging up, as Mark suggested by removing the belt and checking the free play.
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### Author:  [@vanguy16](https://59plymouth.net/u/vanguy16)
#### Post date: [June 18, 2022, 10:52pm UTC](https://59plymouth.net/t/drive-belt-wobble/3818/9 "2022-06-18T22:52:18Z")
Man that is a nice looking 318.
I will check tightness. I don’t like the fact the alternators on a large arm that I think might even have some give when you really tighten the belt. I will also check the alternator pulley.
Thanks guys.
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### Author:  [@Faulkner](https://59plymouth.net/u/Faulkner)
#### Post date: [June 18, 2022, 11:39pm UTC](https://59plymouth.net/t/drive-belt-wobble/3818/10 "2022-06-18T23:39:23Z")
> [@](#):
>
> I don’t like the fact the alternators on a large arm that I think might even have some give when you really tighten the belt.
Mike, that could be the problem right there. At certain engine speeds, that extended arm could vibrate at its “natural frequency” and exhibit the fan belt motion you are observing.
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### Author:  [@Dick\_Koch](https://59plymouth.net/u/Dick_Koch)
#### Post date: [June 19, 2022, 1:39am UTC](https://59plymouth.net/t/drive-belt-wobble/3818/11 "2022-06-19T01:39:29Z")
Could be the v belt itself, you should carry a spare anyway. I have saved at least two Chevy’s with my spare belt.
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### Author:  [@RICKYMOPAR](https://59plymouth.net/u/RICKYMOPAR)
#### Post date: [August 1, 2022, 2:11am UTC](https://59plymouth.net/t/drive-belt-wobble/3818/12 "2022-08-01T02:11:14Z")
**Install a 3/8" belt, Gates or Dayco, re-tension and I think your problem will cease. Rick**
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### Author:  [@vanguy16](https://59plymouth.net/u/vanguy16)
#### Post date: [February 11, 2023, 4:37pm UTC](https://59plymouth.net/t/drive-belt-wobble/3818/13 "2023-02-11T16:37:56Z")
Ricky, by 3/8 you mean a thicker belt? Can’t really go wider
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### Author:  [@Dick\_Koch](https://59plymouth.net/u/Dick_Koch)
#### Post date: [February 11, 2023, 6:50pm UTC](https://59plymouth.net/t/drive-belt-wobble/3818/14 "2023-02-11T18:50:41Z")
I think Rickey is right a 3/8" wide belt should do it… Tighten so there is 3/8 to 1/2 " movement on belt between waterpump pully and alternator pully.
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### Author:  [@RICKYMOPAR](https://59plymouth.net/u/RICKYMOPAR)
#### Post date: [February 12, 2023, 4:55pm UTC](https://59plymouth.net/t/drive-belt-wobble/3818/15 "2023-02-12T16:55:25Z")
The 3/8" belt is thinner and lower in the shieve groove, making it less reactive to small imperfections, less HP to drive. Worth a try.
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### Author:  [@vanguy16](https://59plymouth.net/u/vanguy16)
#### Post date: [March 23, 2023, 1:41am UTC](https://59plymouth.net/t/drive-belt-wobble/3818/16 "2023-03-23T01:41:06Z")
So 3/8 wide it is then, not thick?
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### Author:  [@RICKYMOPAR](https://59plymouth.net/u/RICKYMOPAR)
#### Post date: [March 23, 2023, 1:49am UTC](https://59plymouth.net/t/drive-belt-wobble/3818/17 "2023-03-23T01:49:57Z")
Correct, and less weight/reactive.