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 [img]/ubbthreads/images/graemlins/naughty.gif[/img]

[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.