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  #1  
Old January 18th, 2020, 04:02 PM
linuswilliams linuswilliams is offline
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Default Clunking and Brake Light Question

Hi Guys I have a stock 67 that I'm wrapping up the restoration on. I have a couple of questions.

1. During take-off, my (completely stock) truck has a clunking sensation in 1st gear. As I release the clutch the truck violently rocks forwards. It feels like the driveshafts are struggling to transfer energy to the rear differential. Once in second the clunking starts to resolve itself and by third gear it's completely gone and the ride is smooth. At first I thought the clunking was normal but now it's a pain to deal with and starting to worry me. I have not replaced the ujoints and am wondering if that would help. Does anyone have any ideas on how to fix this?

2. I am trying to determine what activates the brake lights. Generally, there is a switch under the dash connected to the pedal. Mine does not have anything so it either did not have one or is activated differently. Can anyone advise me on what activates the brake lights? Also, is there any way to determine if your turn signal switch is bad?


https://www.instagram.com/p/B7PHNRZhxp1/

https://www.instagram.com/p/B3ZekqIhIMa/

Last edited by brute4c; January 20th, 2020 at 05:33 PM.
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  #2  
Old January 18th, 2020, 06:05 PM
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Don Cavey Don Cavey is offline
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Quote:
Originally Posted by linuswilliams View Post
Hi Guys I have a stock 67 that I'm wrapping up the restoration on. I have a couple of questions.

...

2. I am trying to determine what activates the brake lights. Generally, there is a switch under the dash connected to the pedal. Mine does not have anything so it either did not have one or is activated differently. Can anyone advise me on what activates the brake lights? Also, is there any way to determine if your turn signal switch is bad?


[IMG]https://www.instagram.com/p/B7PHNRZhxp1/
https://www.instagram.com/p/B3ZekqIhIMa/[/IMG]
Isn't there a brake light switch on the "Tee" mounted on the frame which activates the brake lights?
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  #3  
Old January 18th, 2020, 06:05 PM
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Don Cavey Don Cavey is offline
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Activated by brake line pressure. I don't remember a switch on the pedal.
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  #4  
Old January 18th, 2020, 06:46 PM
graflex graflex is offline
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For the brake light and turn signals, did you position the 3-lever switch to turn them on? I know it sounds like a stupid question, but you would not be alone in forgetting this.

Wayne
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Old January 19th, 2020, 06:40 AM
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Quote:
Originally Posted by linuswilliams View Post
Hi Guys I have a stock 67 that I'm wrapping up the restoration on. I have a couple of questions.

1. During take-off, my (completely stock) truck has a clunking sensation in 1st gear. As I release the clutch the truck violently rocks forwards. It feels like the driveshafts are struggling to transfer energy to the rear differential. Once in second the clunking starts to resolve itself and by third gear it's completely gone and the ride is smooth. At first I thought the clunking was normal but now it's a pain to deal with and starting to worry me. I have not replaced the ujoints and am wondering if that would help. Does anyone have any ideas on how to fix this?

2. I am trying to determine what activates the brake lights. Generally, there is a switch under the dash connected to the pedal. Mine does not have anything so it either did not have one or is activated differently. Can anyone advise me on what activates the brake lights? Also, is there any way to determine if your turn signal switch is bad?


[IMG]https://www.instagram.com/p/B7PHNRZhxp1/
https://www.instagram.com/p/B3ZekqIhIMa/[/IMG]
1. Could be bad u joints in the driveshaft that are clunking under pressure. With the truck parked and brake set, crawl under and grab the driveshafts and try and rotate them back and forth. If there is play then look to see where the slop is. If it's at a u joint then replace it.

2. The brake light switch is a pressure switch mounted to the frame rail below the master cylinder where the brake lines T off. There should be a rubber cap on the T that has 2 wires coming up and out of it.
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  #6  
Old January 19th, 2020, 08:04 AM
linuswilliams linuswilliams is offline
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Thanks Don, I'll check.
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  #7  
Old January 19th, 2020, 08:08 AM
linuswilliams linuswilliams is offline
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Awesome info. Thanks. I will check this out.
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  #8  
Old January 20th, 2020, 06:01 PM
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Just as a check to eliminate any clutch or other odd driveline problems...

If you are on flat ground, drop the truck into 1st gear, turn on the on/off switch. Do not push in the clutch pedal or step on the brake and hit the starter button.
The truck should crank and pull itself forward and start...

If the jerking goes on, even when it is just cranking, I would change the u joints...they are all the same and a 369 joint is the part number...that should fit the front, center and rear drive shafts.

It might be quite rough when you crank this way if the ujoints are bad...if they are good, it should spin and start easy with no real jerking.

Let us know what you find.

As far as the brake light switch, it is as said a pressure switch on screwed into the side of the brass block mounted on the frame below the master cylinder where the line from the master goes down to and then splits to the 2 front brake lines and one line to the rear...unfortunately, there does not appear to be a single image in the manuals showing this...
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  #9  
Old January 20th, 2020, 07:11 PM
linuswilliams linuswilliams is offline
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Thank you so much. I will try this. Much appreciated.
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  #10  
Old January 21st, 2020, 06:42 AM
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That driveline slop might be a pinion issue at the rear axle, also. Grab the rear u joint & try and move it side-to-side; it should exhibit the slightest movement and no more.
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