Speedo reducer what's it for
 

Anybody know what this reducer is for ?
666F V8
.9444W

Thanks for your help
Ken

Low Rear Gear cars.

My Guess later model Truck after 1970 with 4.10 gear ratio.
Checked eBay completed items and one sold for $64 but had no info at all for what it was for.

There are charts from GM that show when a particular combination of trans and wheel-tire size got a particular part number reducer. The part number is not one of the numbers you listed. you have to do a bit of google searching to cross reference the GM part number to the reduction number, in your case the .9444.

Here's an example for a 1970 Camaro,Chevelle, Nova 4 speed cars:

http://www.gmpartswiki.com/getpage?pageid=12662

If you plan on actually using it, you would be advised to open it up and clean out and re-pack the grease. It dries out over time.

I found one guy selling a reducer
and claiming it's for LS6 410 rear
666F V8
.8241C
maybe mine is for 456 rear ?

A friend here in Calgary gave me one that I used in the green 4:10 gear car I recently finished. They work well if you know what gear conversion they were intended for.

If you repack it with grease use a light grease. Otherwise the load can snap the tab on the drive gear clip inside the tail housing.

Are these also used on the automatic cars, mine came with 4:10 gears but someone put in 3:73 gears. If I return to the factory gears I will have to get a reducer.Thanks

I have a box full of those, there was two different kinds. Mostly for trucks.

Speedo Reducer...
 

Yes auto cars got these as well.

The Yenko Deuce Novas also received them, specifically the round style that has a superceded part # 1565208 with a 1 : .833 ratio for the 4.10 gears.

I have a rounded version with .6481 stamped on it. I pulled it from the same car I pulled a BX code 4.88 rear from.

I've never been able to accurately cross that gear reducer number to anything but it does work accurately with that rearend.

The round reducer with 1:.833 is #6477965

Did the Copo's and Z/28's with 15 inch tires use a reducer with 4:10 gears?

On some cars too with 3:73's

My 1974 z/28 4 speed has that same reducer on it. Its definately the original reducer. Im sure I have 3.73 rear

Here are pics:

Not on Z's. Never seen a 69 Z with one (though they may be out there). Only on first gen Z's with 4.56 and 4.88 axle.

Most I've seen were in BB cars and most were 14" tires. It depended on which trans version they received - there were different speedo drive gears (shown in that chart).
I've seen 2 different adaptors used in 69 - auto vs manual - but there probably were others for the special order 4.56 and 4.88 axles.

My turbo 400 70 Z with 3.73’s has one.
Buddy

My 70 4 speed car has one also. But I have seen many other 70Z's without one.

What I never could understand is the chart I attached a link to. It shows cars with a wide ratio (M20) getting one but cars with a close ratio not getting one. What difference does the trans ratios make??? The internal speedo gears are driven by the output shaft so the gears in front of them make no difference. Not to mention that in 4th, all Muncies were 1:1 anyway. Am I missing something here?

Sorry, clarified that I was only talking 67-69.

I'd say no for my 68 Z with factory 4:10 ratio doesn't have the reducer because of the 15" tires.