Johns_65Vette

I copied the numbers off of the trans and diff on my 65. Is the Vin# usually stamped onto the trans? Not sure how all these decode but here goes.
Cars Vin is 194675S101340.


Trans:

Stamped numers 19S720103 P9C11B
Casting number 3925660

There is also a little metal tag on the cover. Not sure if the first number is a 3 or not

Tag: (3?)946798
________________________________________ __________________

Rear diff:

AP 9 1764

I assume the 1764 calculates into the ratio? 3:73? Not sure what the AP 9 means though.

RGGregory

Actually, AP is the code for the r-end ratio - in your case 4.11! How many rpms are you pulling at 40 or 50 mph? 9 17 64, should be the assembly date of the r-end - Sept 17th, 1964.

RGGregory

I don't have all my references at home, but I don't think the transmission in the came with it, based on your VIN#. I think the "S" number should be S101340, as the VIN derivative. There is a website, which I can't recall right now, that has all the muncie # deciphering you could ever want...try a search, or hopefully another forum member will be along with the website URL or a translation of the rest of your numbers.

A quick google search found this website:

http://www.5speeds.com/muncie2.htm

Looks like you have a 68-70 main case..I say main case, because depending on the wear and tear on the car previously, you could have a transmission made up of multiple donor units.

Johns_65Vette

It is screaming on the freeway 3500RPM@about 68/70 MPH

Thanks for the info Time for a Keisler 5 Speed

RGGregory

I don't think you have a 4.11 then. What size tires are you running? My former 67 with a 3:70 turned about 4000 rpm at 70-ish, and I verified the ratio. Jack up the rear of the car, put it in neutral and turn the the rear wheels. If you need to, put a temporary mark on the driveshaft to help count rotations. Rotate the wheels completely several times while counting the number of driveshaft revolutions. Divide the # of d-shaft turns by the number of wheel turns...you get your rear-end ratio.

This measurement method will overcome any errors in your speedometer and/or tachometer

PS - it will be easier to stop counting on a full rotation of the driveshaft, since with the tire right in front of you and with a bigger diameter, it will be easier to determine what fraction of 360 degrees the last tire turn was (that's why turning the wheel more than one time will help - the more turns, the easier it will be to discriminate between 3.55, 3.70, 4.11, etc.

http://forums.corvetteforum.com/show...285&forum_id=4 this recent post is on the ratio counting thing..same topic comes up at least once a month, it seems.

JohnZ

The trans is out of a '69 Corvette built in late March '69, and the trans was built on March 11th - it's an M21. The diff is a small-block 4.11 Posi built on September 17, 1964 for a '65.

Johns_65Vette

Thanks oh Masterful one

stratplus

I am not sure what this tells me. I spun the tire 3 times and the driveshaft turned 5 times. This is a non posi. So what is the ratio?

JohnZ

Did you just turn one tire with the other one stationary, or did you turn both of them the same amount?

stratplus

I only turned the drivers side tire 3 times.

joseph p

From what I remember in the old '70s, we used to go by 60MPH=3000RPM with 4:11 and 3500RPMs with 4:56s.

mr55

how rare are the c1 gearbox 3708184 gm 1 k 54

silver837

13 year old post, Best to start a new thread. Early C-1 followers will respond .