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Discussion Starter #1
The assembly manual shows a reducer inline between the speedo cable and transmission on a muncie.

I've been told they were not used for all rear end ratios. What applications used the reducer?
 

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I've never seen one on a car - possibly used on 4.56's? (I've never seen a factory-installed 4.56).

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JohnZ
'69 Z28 Fathom Green
 

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Yes, there is a reducer.

I bought one, but can't remember the part number, 393XXXX,

There is a post in Engine and drivetrain, that's where I got the part number.

It was installed on 4.10 and higer numerical ratios. I used a 20 or 22-tooth gear. The post had the parts.

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Everett 68/350/PG/11.90/115mph
 

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I have one that I got at a swap meet. I bought the drive pin at a local Chevy dealer.
I just don't know if I need it with my 3.73 rear.
 

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NPD sells the the gears to go in the reducer for about $8.oo.

There is a red,blue,greeen, black, Orange and yellow gear depending on your rear end gear ratio.

You might want to call them to see if the have a reducer. the N. Carolina # is 704-331-0900

Tony

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obnoxious 67 camaro under construction. TH350/383 stroker w/ aluminum Edlebroc RPM heads,cam, and carb.This is a "Daily Driver" that need A LOT of work. But has new quarters and new floor pans.
 

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It wasn't used with the factory 4.10 axle; my original 4.10 didn't have one. When I changed it out to a 3.55, all I had to do was change the original 25-tooth driven gear to a 22-tooth.

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JohnZ
'69 Z28 Fathom Green

[This message has been edited by JohnZ (edited 11-23-2001).]
 

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John Z. How do you know someone just didn't remove it at one time or another? I have a 69 Z with a 4.10 rear and it had it.
 

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I dunno - maybe some did, some didn't; although it shows in the A.I.M. in the G80 Section (Positraction axle), it doesn't show the specific usage where it's required (which ratio, etc.) except for one L34/M40 application that requires a different adapter than the other two shown. All I know for sure is that mine is an original factory 4.10 (have the documentation), has never been touched since it was built, and it didn't have one. If someone knows the specific applications that required it, that would help answer the question. As I said, I've never seen one on a '69 Z/28, but I've never seen a factory-installed 4.56, either.

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JohnZ
'69 Z28 Fathom Green
 

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You can get some idea of what cars came with the adapter if you look at Group 4 of the parts book(back section). For the 4 speed in 69 with E70X15 tires it does not show that an adapter was used for the 3.73 or 4.10.
 

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Good tip, Secondgn - we (CRG) did an informal survey last night and today, and there's no concrete documentation on exactly which cars got it and which cars didn't. The speedo gear arrangement was dictated by tire size, rear axle ratio, and which drive gear was on the trans output shaft - we do know that some Muncies had a 1.750" diameter drive gear and some had a 1.850" diameter drive gear, but there's no apparent pattern to internal drive gear usage that's tied to any other option condition or different transmission part numbers. I guess the best answer at this stage is that some combinations needed it and some didn't, but we don't have any way right now to nail down why. The cars that took the adapter/reducer also used a shorter speedo cable unique to the adapter usage (GM# 3839896); if we had the original releasing information for this cable it would show what conditions dictated its usage, but that stuff is long gone. The search goes on......that's what we do.

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JohnZ
'69 Z28 Fathom Green
 

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Thank you, bilydean, I appreciate the remembrance.

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Everett 68/350/PG/11.90/115mph
 
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