Help with Muncie speedo gears

**SS427** · #1 11-27-2018, 02:47 PM

As many may know, our 69 Chevelle when found was missing the M21 so I took one off the shelf that I had (originally came out of a Pontiac) and rebuilt it using the correct Chevelle tailhousing. What I am not sure about is what speedometer drive and driven gear I need for the 4.10 with F70x15 tires. From talking with Eric at Crash Enterprises we came up with a small 8 tooth metal drive gear and a large yellow 24 tooth driven gear when used in conjunction with the .7333 speedo reducer. Can anyone else concur with this information before I put it all back together or offer other insight? I also could use part numbers if you have them.

Another question, does the 69 4.10 car use the offset BW rectangular adapter or the round 90* adapter? Thanks in advance for your help.
Rick

fsc66 · #2 11-27-2018, 05:01 PM

Rick,
will any of this help?
https://www.cartechbooks.com/techtip...e-speedometer/

Paul

x33rs · #3 11-27-2018, 05:02 PM

I did the math and with an 8 tooth drive gear, and a 27 inch tall tire (746.96 revolutions per mile) it is in fact a 24.47 driven gear that you need.

24 will work fine.

**SS427** · #4 11-27-2018, 05:21 PM

Yes and no. I had been there already and it helped but not completely. The real stickler that I am dealing with is that the car came with F70x15 NOT F70x14 which is a different diameter and it throws a slight wrench into things. Same for the speedo reducer.

**ssl78** · #5 11-27-2018, 06:21 PM

my 69 4:10 Chevelle uses the straight adapter.

**SS427** · #6 11-27-2018, 06:23 PM

Interesting John. M22 or M21? Do you have a photo of the adapter by chance so that I can see what the straight one looks like? Thanks

**ssl78** · #7 11-27-2018, 06:34 PM

m22 trans. As far as I know the reducer was original but who knows I bought the car in 1991 any thing could have happened before that.

**SS427** · #8 11-27-2018, 06:56 PM

Ok, good. That is the same SW piece that I have though I have not confirmed which ratio I need yet with the F70x15. Thanks for posting that John.

**ssl78** · #9 11-27-2018, 07:53 PM

Would it be the same ratio as a Yenko Camaro. Doesnt Chad have any pictures of his adapter from the blue Yenko Chevelle

**SS427** · #10 11-27-2018, 08:15 PM

I haven't had a chance to call and ask him yet. I have several but of course, the one area of the transmission I did not take a photo of was the adapter. Go figure. I got a great shot of the XF trans stamp on the top but no adapter.

As far as being the same as the Camaro I do not know why it would not be. M21, 4.10, F70x15, all things being equal. The gears I posted at the beginning were the Camaro ones but just trying to confirm.