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Old 11-26-2022, 01:36 AM
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Default Correct Speedometer Adapter 67 L78 D70-14 4.56 Rear

Hello Folks,

What is the correct factory speedometer adapter needed for my 1967 Camaro SS L78 with 4.56 rear and D70-14 tires?

It may take me a long while to find the correct original and I'd like to start the hunt now but need confirmation on the correct part number.

Thanks!

Jose
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Old 11-26-2022, 01:52 AM
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I think 4:56 used 735. 736 was used for 4:10 and 4:88
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Old 11-26-2022, 03:55 AM
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Yep just found that the 735 is the one I need. Thanks
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Old 11-27-2022, 03:11 AM
Big Block Bill Big Block Bill is offline
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Who needs a speedometer when you’re running 4:56 gears, just listen to the music the motor is making and guess! But I’m just sayin.

Bill
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Old 01-18-2023, 03:44 PM
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Adapter Found. Thanks everyone
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Old 01-18-2023, 09:15 PM
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An adapter p/n 6476655 was first listed in the July-67 parts book, but only for 67 Z28 (7.35x15 tires) with 4.88 gears. See: http://www.gmpartswiki.com/getpage?pageid=10455

The line above that lists p/n 3905497 as "67 Camaro (4-spd, w/ P/Trac.) (350)", without any ratio references. And it says "driven gear" rather than "Adapter Assy". But that is not correct, as p/n 3905497 shows up in Chev. truck parts books through at least 1979, listed as an adapter.

So I assume that was the very common bad data entry in the parts books when an item was first used. If so, perhaps 6476655 was an adapter for 67 Z28's with 4.88, and 3905497 was an adapter for all OTHER manual trans 67 Camaros (with 14" wheels) that required an adapter (so 4.10, 4.56, AND 4.88 ??) But see below that suggests that the July-67 listing may be even more wrong than that.

***
The page posted earlier above is from the November-67 book (so issued after 1968 production had started and part numbers may have changed). For 6476736, it continues the incorrect "driven gear" description, but changes the applications to all Camaro 4-Spd with 4.10 or 4.88 (without any model or tire limitations).

Then it lists 6476735 as 4.56, but limited to Z28 only (7.35x15 tires) -- So the "Z28 only" listing shifted from 4.88 gears in the prior book to 4.56 gears in this one. But you could also get a 4.56 behind a 350 or a 396/375, so the limitation to Z28 tires would leave all other 4.56's with no adapter.

If the Nov-67 descriptions are off, and 6476736 is ALL manual Camaro 4.10 and 4.88, and 6476735 is ALL manual Camaro 4.56 (and not just Z28), then that begs the question whether the July-67 book's reference to one adapter (6476655) for Z28 4.88 only was really for all manual Camaro 4.56's, and the other adapter (3905497) was really for all manual Camaro 4.10's and 4.88's ???

***
On a related question, does anyone know for sure whether any adapters were originally used at all on any 66 and 67 Chevelles? I have a factory 4.88 67 Chevelle. There was no adapter, but when I got the car the engine was gone and the speedo cable was hanging loose. So there could have been one that was tossed.

Given that final drive ratios on a Camaro and a Chevelle with the same trans, rear gear, and tire circumference would be exactly the same, it seems logical that if a 67 Camaro needed an adapter for the 4+ ratios, then a Chevelle should have needed one too.

But there is nothing showing an adapter in the Chevelle AIM for 66 or 67. And in the Chevelle parts books, Group 4.329 (where the adapters are listed) did not have any adapters listed in the Oct-66 and prior books, except for Corvairs. See here: http://www.gmpartswiki.com/getpage?pageid=77360

The first time an adapter shows up for a Chevelle is on the page posted earlier above from the Nov-67 book. And it only references usage on 68 Chevelles, but still no 66-67 Chevelles applications.

So the books suggest no adapter on 66-67 Chevelles, but that defies logic if a Camaro needed one.

Thanks!
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Old 01-18-2023, 09:43 PM
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Default 67 l78 Camaro 456 rear trans adapter.

Jeff for reference there is an unrestored example with a 6476736 .777 adapter. The variable is the all important drive gear. My car is also equipped with 456 and when purchased did not have an adapter and the speedometer reading is accurate. In a few months I will have access and will know what driven gear is in the original transmission.
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Old 01-18-2023, 11:18 PM
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Looking at the parts history it seems that the part numbers 735 and 756 adapters "appear" in November 1967 since they replaced older part numbers 655 and 497 in August of 1967. Perhaps I bought the wrong part?
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Old 01-18-2023, 11:20 PM
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Quote:
Originally Posted by Steve Shauger View Post
Jeff for reference there is an unrestored example with a 6476736 .777 adapter.
Is that picture a Camaro? What year? And what rear gear?

Quote:
Originally Posted by Steve Shauger View Post
My car is also equipped with 456 and when purchased did not have an adapter and the speedometer reading is accurate.
Is yours a 67 Camaro? L78 or Z28?

Thanks!
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Old 01-18-2023, 11:33 PM
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Quote:
Originally Posted by jbtech View Post
Looking at the parts history it seems that the part numbers 735 and 756 adapters "appear" in November 1967 since they replaced older part numbers 655 and 497 in August of 1967. Perhaps I bought the wrong part.
Thanks! I should have thought to look at the superceded numbers book too! Very helpful.

That page does suggest that the July-67 book is wrong where it says 6476655 was for 4.88 Z28. Since it was replaced by 6476735 (which is 4.56), presumably 6476655 was also for 4.56.

Likewise, since 3905497 was replaced by 6476736 (which is 4.10 and 4.88), presumably it was also for 4.10 and 4.88.

However, since 67 Z28 tires are presumably taller than the regular 14" tires, maybe a 4.88 with 15" wheels was close enough in final drive ratio to a 4.56 with 14" tires, so used the 4.56 adapter?? If so, then the July-67 book would be correct on that one application, but the Nov-67 book would have to be wrong. I don't see how they could both be correct ...
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