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Click on image for the lowdown. 
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| | | Forums66 Topics128,162 Posts1,056,950 Members48,458 | | Most Online14,466 Apr 26th, 2026 | | AD Chevy Trucks Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
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For helping keep this great
old truck web site
on the Internet for over 30 years! and not clogged down with Ads! Again, thanks! | | | | Joined: Dec 2015 Posts: 2,063 Big Bolt Forum Moderator | | Big Bolt Forum Moderator Joined: Dec 2015 Posts: 2,063 | Working on my 55 and 58 2-tons. (model 6400) the vacuum diaphragm actuator for the speedometer adapter is shot. Does anyone make replacement diaphragms, or do you modify a vacuum advance module to activate it or what is the fix? | | | | | Joined: Oct 2012 Posts: 60 Shop Shark | | Shop Shark Joined: Oct 2012 Posts: 60 | I used a 3M sealant (glue) used for attaching rubber trim to cars. I took apart the unit, cleaned well and applied several thin layers to the outside and inside. This fix held vacuum and I have since found a NOS part on Ebay. | | | | | Joined: Dec 2015 Posts: 2,063 Big Bolt Forum Moderator | | Big Bolt Forum Moderator Joined: Dec 2015 Posts: 2,063 | you applied the glue to the inside and outside of the rubber diaphragm? I will see if one of mine is good enough for that, may not be enough rubber left! Do you remember what the official name of the part is called? | | |
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