Yenko turbo 400 speedo adaptor

[fpcopo]

Hi,
Does anyone know the ratio or the part # for the speedo reduction box on a T400 Yenko Camaro with 410 gears and the E7015 tires? Also any idea on the color or teeth of the speedo gear? Thanks

[Mr70]

Although you want TH400,the book says for TH350 use #6476736 with 4:10 E70X15 tires.I know one who used this with good results.
Gear color is Orange #3860348 with 25 teeth.

[JBB]

That is the Stewart Warner speedo reducer for 4.10 ratio rear and higher. Send me a e-mail and I will send you a picture of the proper part..............Joel /ubbthreads/images/graemlins/naughty.gif

[copo69]

I'm confused. I thought the'69 Copo 15" E70 cars didn't use an adapter, only the 14" tired cars. Was this only manual shift cars or autos too? Did auto cars use the square adapter or the cylindrical shaped adapter used on the manual trans cars? I know Brian made the statement he had never seen one used on a Yenko.

[JBB]

Hi everyone. The tire size is not the issue, it is the size of the speedo gear 4.10 or higher that couldn't fit inside the transmission casing, so that is the only purpose of the transducer.............

[JBB]

Just to reiterate, we are talking about a CX TH400, specifically behind any solid lifter big block in 69

[JoeC]

I believe the reason for the Speedo adapter was to get correct Speedo reading within federal tolerance. Adapter use was not governed by the gear ratio but by the gear tire trans combo. If you go one tooth up or down on the speedo gear in the trans it is about a 5 mph change. With the Speedo adapter if you go one tooth up or down on the gears in the adapter it is an about a 2.5 mph change. Some tire trans gear combos needed the adapter to get correct Speedo reading. My Yenko Chevelle TH400 4:10 gear has original trans with adapter and the Speedo reads correctly.

[JBB]

You are right Joe, it is to give the proper speed on the speedometer. But the only way to achieve this is the use of the Stewart Warner unit, as a 4.10 or bigger speedo gear could not fit in the casing. This info is per a transmisssion specialist, who has been rebuilding transmissions since the early 60's............

[copo69]

Well, do all 4:10 or lower geared cars use adaptors or only 14" tired cars? Auto's different from 4 speeds?

[COPO]

Believe it is all 4.10 and greater got the adapter regardless of trans type. My 70 Z-28 w/4.10 also has the adapter and it came with 15" wheels.

[Kurt S]

No, not all Muncies hooked to a 4.10 got the adaptor. Depended on which Muncie model it was, there were two different size speedo drive gears.

[copo69]

Should the 9737 Camaro with 4 speed have the adapter? 9737 with auto?

[Ed Cunneen]

Yes

[Unreal]

Is this the little 90 degree adapter that shows on the AIM? I have one, but was not sure if I should be using it.

[Mr70]

That sounds like it.

[Unreal]

So with 235 70 15 tires and a 3.73 rear, will I need it?

[Mr70]

With a manual transmission, No.

[Kurt S]

[ QUOTE ]
Should the 9737 Camaro with 4 speed have the adapter?

[/ QUOTE ]
Maybe. Some 4.10 rears got them, some didn't. Depended on plant inventory. I have documentation on several Z's with 4.10's and no adapter. Tire size shouldn't be a factor, but Z's had 15x7's anyway.

[JBB]

This part:
Stewart Warner
GGGF X1 (or 666F X1)
1.300 J
Is specific to a solid lifter L-78,L-89,4.10 or higher w/TH400.
It is manditory for a COPO L-72 or ZL-1 w/TH400 in leiu of the fact a 4.10 was standard rear,with higher gears optional. I am not sure of the M-22 or M-21 4 speed application............

[Ed Cunneen]

I have a speedo reducer chart on my web site rl=http://www.copo.com/speedo-reducer.htm

[ssl78]

This is out of a 69 chevelle 396 350h.p. This was an all original car that came with a 4;10 rear end in it.It looks like the part number was 6666F N1 See attachment

[Rat_Pack]

Ed, is there something wrong with your site? I have tried for the past few days to get onto it and it says I do not have the credintials to view it. Never had that problem before.............RatPack..................

[Ed Cunneen]

My provider switched over to a new server. I believe you just need to clear the cashed pages and the site should come back up. Email me at [email protected] if you still encounter problems.

[Kurt S]

I politely disagree with Ed's statement that all 4.10 manual cars had an adaptor. /ubbthreads/images/graemlins/smile.gif
As I said up above, there were 2 different Muncies (with 2 different part #'s) with 2 different size speedo drive gears. One needed the adaptor with a 4.10 gear, one didn't. Usage was apparently driven by availability. So, it's a crap shoot if a manual / 4.10 car had an adaptor originally.
Don't think it's on the CRG site, but we've discussed it at length. Ask Jerry MacNeish, he's rebuilt hundreds of these trans' and is very familiar with the issue. And I have broadcast sheets that clearly show 4.10 cars without the adaptor.
I'm pretty sure all 4.56 and 4.88 gears had the adaptors.

No idea on the auto.

[Ed Cunneen]

Kurt,
My information relates specifically to COPO's. The chart on my website which shows speedo adapters relating to COPO's is a reference that came directly from the COPO build orders. My interpretation of this is that all specifically referenced COPO's had this reducer. Perhaps it is because they all were ordered with the same type of transmission. I then listed the chart that came directly from Chevrolet parts for COPO's that had 4-speeds with certain tire combinations. Since these combinations were RPO's and not deviations, it was not necessary for Chevrolet to list them in the COPO build order. I have never encountered a variation from the above, but if we find exceptions, I would be happy to add them to my site.

[Kurt S]

Thanks for mentioning the source of the info.
I'll defer to you as I don't have any L72 chassis broadcast sheets nor have I looked at *that* many L72's. /ubbthreads/images/graemlins/smile.gif

BTW, I've found some of the factory info can be in 'error'. Only one build option will be listed, though another build option/combo is possible.