1965 M20 Speedo Connection

[Glenn Rogers]

Did all Corvette 1965 Muncie M20 Wide and Close ratio 4-spds have the speedometer cable connect on the driver's side?

Thanks.

[Joe L.]

Re: 1965 M20 Speedo Connection

Glenn-----

No, 1965 was a year-of-change for this feature. Until early 1965, the extension housing had the speedo gear fitting on the passenger side. After early 1965 (about February, 1965) the extension housing changed and the fitting was on the driver's side. It remained there forevermore.

[Wayne M.]

This urban legend survives

This bit about early '65 model year 4-speed Corvettes with "429" tail housings (driver side connection, different [shorter] speedo cable and no support clips on RH passenger tunnel or firewall is completely false.

I blame A. Colvin's book for originating this story. I have NEVER seen an early 4-speed factory '65 Corvette without a "584" tailhousing (passenger side connect on speedo cable). My # 014xx (Nov 6th, 1964) is proof, but I've seen many others.

[Glenn Rogers]

Re: 1965 M20 Speedo Connection

Joe .... thanks. My car was an early April 65 build and it has it on the right passenger side. There is also what looks to be a factory original clip to secure the cable on that side (to keep it off the exhaust pipes). Although my tag code 3856436 (third up from the bottom of the list below) shows it to be for a 65 passenger M20 V8, I wonder if (during this transition period in 1965) the production line may have had to grab similar (if not identical ) trannies from the passenger line in some cases?

This listing was posted by someone else on another forum. I don't know how accurate it is because it also lists 1964 M21 units, which I did not realize existed with that designation before 1965 or 1966 for the Corvette line.

CORVETTE
63 3831703 M20 ........................................ ..................
63 3831701 M21 - 327/L76 & 327/FI ...........................
64 3839602 M20 (exc. 327/L76 & 327/FI) ...................
64 3839601 M21 - 327/L76 & 327/FI ...........................
65 3857580 M20 (exc. 327/L76 & 327/L79 & 327/FI)
65 3857573 M20 - 327/L76 & 327/FI ...........................
65 3857579 M20 - 327/L79 ........................................ ..
65 3857581 M21 - 327 & 396 ......................................
65 3879986 M22 - 327/L76 & 327/FI ...........................
65 3879987 M22 - 396 ........................................ .........
67 3870354 M20 - 327 & 427 ......................................
67 3880853 M21 - 327/L79 ........................................ .
67 3880855 M21 - 427 (exc. L88) ................................
67 3879987 M22 - 427/L88 ........................................ .
68 3915088 M20 - 327 & 427 ......................................
68 3915090 M21 - 327/L79 ........................................ .
68 3915091 M21 - 427 (exc. 427/L88) .........................
68 3915093 M22 - 427/L88 ........................................
69 3950356 M20 - 350 & 427 .....................................
69 3946798 M21 - 350/L46 ........................................
69 3950316 M21 - 427 ........................................ ......
69 3946799 M22 - 427 ........................................ ......
70 3952659 M20 - 350 & 454 ......................................
70 3968011 M21 - 350/L46 & 454/LS7 ........................
70 3968012 M22 - 350/LT1 .......................................
71 3968011 M21 - 350/LT1 & 454 ...............................
71 3978766 M22 - 350/LT1 & 454 ...............................
72 6271518 M21 ........................................ ..............
72 6271517 M22 ........................................ ..............
73 6271516 M20 ........................................ ..............
73 6271518 M21 ........................................ ..............
74 6271516 M20 ........................................ ..............
74 6271518 M21 ........................................ ..............

PASSENGER
63 3831819 M20 - 327 ........................................ .........
63 3831821 M20 - 409 ........................................ .........
63 3831823 M21 - 409 ........................................ .........
64 3841435 M20 - 327 & 409 ......................................
64 3844059 M21 - 409 ........................................ .........
65 3856436 M20 - V8 ........................................ ..........
65 3856435 M21 - 396 & 409 ......................................
65 3879989 M22 - 396 & 409 ......................................

[Joe L.]

Re: This urban legend survives

Wayne-----

It's very possible that no 1965 Corvettes were ever built with a Muncie '429' extension housing. I've never studied the matter, at all. According to GM sources, the only extension housing used for 1965 was the '584'. However, there are quite a few sources that indicate that the '429' was used for early 1965, so it's not just Colvin's book that references that information.

Also, the 1965 AIM, on UPC M20, sheet 4 shows a right side speedometer fitting.

[William C.]

Re: This urban legend survives

There are a number of other changes that have to be made to facilitate this change that combine to make it very unlikely it was an other than start of production timing, the speedo cable is changed the routing is changed and clips are relocated, and all this has to be co-ordinated when the "new" trans configuration would have arrived. The assy plant would have fought this tooth and nail to keep from co-ordinating all these things at one time. Pontiacs used the 429 for many years, but I agree with Wayne, I've owned '65 cars as early as S/N 838 and all had the pass side speedo configuration.

[Joe L.]

Re: 1965 M20 Speedo Connection

Glenn-----

There are all sorts of possibilities here. If the transmission has the car's VIN derivative stamping and the stamping appears reasonably authentic, then something like what you suggest must have happened OR the transmission part number was one regularly used for Corvettes, notwithstanding the list you provided.

As I mentioned previously, while there were a plethora of transmission part numbers (which, incidentally, is completely supported by the above listing) there were really only 2 differences between all of the transmissions: (1) the first gear ratio and (2) the installed speedometer gear combination. It was the latter which created the VAST majority of the need for the plethora of part numbers. It may well be that the transmission part number found in your car used a combination of speedometer gears that was used only for passenger cars and it was somehow "pressed into use" for Corvettes. However, MUCH more likely is that it was actually used for Corvettes but that usage is nowhere recorded. As I say, the list of transmission part numbers found in the AIM could not be the complete list of transmissions used for Corvettes since they wouldn't represent nearly enough part numbers to accomodate all of the rear end ratio choices (and, consequently, the required speedo gear combinations).

The RPO M-21 or similar nomenclature was not used before 1966. I expect that the compiler of the above list used it to denote wide and close ratio transmissions for the 63-65 period.

Also, keep in mind that Muncie transmissions used for most Chevrolet passenger cars were exactly the same as those used for Corvettes. The only difference may have been the fact that there may have been different rear gear ratios available in passenger cars as well as different sized tires used. Consequently, there would have to have been different speedometer gear combinations (and, consequently, different part numbers).

[Stephen L.]

Re: 1965 M20 Speedo Connection

Joe, are you sure the speedo cable hooks up on the driver side of an M20? My 67 is on the passenger side, the AIM shows it on the passenger side, and the shift linkage would raise hell with it on the drivers side.....

[Joe L.]

Re: 1965 M20 Speedo Connection

Steve-----

Yes, I said it backwards; on this issue, for some reason it's something I "reverse" all the time. It's like a "mental block", or something. The 63-64 (and, early 65 if any were made that way) used the 429 extension housing with the speedo fitting on the DRIVER side. The 65 to 70 used the '584' which had the fitting on the PASSENGER side.

[Terry F.]

I was starting to worry! *NM*

[John H.]

Re: This urban legend survives

The P&A30B also shows the passenger-side 584 for '65-up in Group 4.317, and the '65 Assembly Manual M20 sheet that shows the passenger side cable, speedo gear, routing and clipping in the initial issue was released in May, 1964, three months before start of '65 production. I know the Colvin books say the 429 driver's side speedo housing was used until February, but I've never seen a '65 with a driver's side speedo either.

[Mike McKown]

Ain't worth nothin'

My '65 Chevy II was built/delivered in December '65 with a left side speedo connection for the speedo cable.

[John H.]

Re: Ain't worth nothin'

Mike -

I agree - built lots of those at Willow Run, but I've never seen a '65 4-speed Corvette with the speedo cable on the left side.

[Dick G.]

Re: Ain't worth nothin'

My first week January 65 car with the 584 tailhousing has it's speedo on the Passenger side. Dick Gutman