Help De-Coding 64 Driveline

[Darwin O.]

Hey Gang!

I was doing the pinion seal on my '64 yesterday, and while I was under there I took down the driveline numbers and have been going through my reference material trying to decode them (still waiting for my 64 judging manual to arrive). Here's what I got:

Bellhousing Casting #: 3840383 (second digit could be a 9, perhaps)

This is the same number that shows up in Noland's book for a L76 engine with an M20, I've got an L75 with an M20. Was this bellhousing used on both?

Tranny Tag: 3839602
Tranny Casting #: 3851325
Tranny Patent #: 3088336
Tranny Tailshaft Housing #: 3846429

Not sure what these mean, does it confirm that it's an M20? Are there casting dates I've missed?

Diff Stamp Pad: CJ 212 64 (3.08 ratio, Feb 12 1964 - 9 days prior to trim tag date)
Diff Cover/Mount Casting #: (3 or 8)8(3 or 8)0303
Diff Cover/Mount Casting Date: B14 (Feb 14th)
Diff Cover/Mount Other Casting: GM5

Anyone know what the correct casting number is for the cover/mount, and what GM5 signifies?

Thanks in advance for any info that you can share.

Cheers!

[Timothy B.]

Re: Help De-Coding 64 Driveline

Darwin,
Rear cover casting # I think is 3830303, this cover is used in 63-64-and early 65. Sounds like you got all the right stuff for the rear, I don't know Muncie transmission #'s. (yet)

[William C.]

Re: Help De-Coding 64 Driveline

Numbers are good for a '64 Muncie, but the ratios were not coded on the trans until later. If it's out you can tell the ratio by looking at the input shaft, no circumferential rings is a wide ratio, one circumferential ring is a close ratio.

[Philip C.]

Re: Help De-Coding 64 Driveline

Darwin,
Rear cover casting # I think is 3830303, this cover is used in 63-64-and early 65. Sounds like you got all the right stuff for the rear, I don't know Muncie transmission #'s. (yet)

Tim your right the rear cover is 3830303, So Darwin disregard the New J/M referernce to its number 3818753 (pape 145) no idea where they got that from. PS Dont forget to put sealer on the pinon splines, more people change a GOOD seal because they think its leaking and its leaking down the splines. Phil 8063

[Wayne M.]

Re: Help De-Coding 64 Driveline

Here's what I got:

Bellhousing Casting #: 3840383 (second digit could be a 9, perhaps)

Tranny Tag: 3839602
Tranny Casting #: 3851325
Tranny Tailshaft Housing #: 3846429

Not sure what these mean, does it confirm that it's an M20? Are there casting dates I've missed?

Diff Stamp Pad: CJ 212 64 (3.08 ratio, Feb 12 1964 - 9 days prior to trim tag date)
Diff Cover/Mount Casting #: (3 or 8)8(3 or 8)0303
Diff Cover/Mount Casting Date: B14 (Feb 14th)
Diff Cover/Mount Other Casting: GM5

Anyone know what the correct casting number is for the cover/mount, and what GM5 signifies?

Darwin --- to add to what others have said, and items not yet responded to:

383 bellhousing -- These have been reported on later '64s and some early '65s. (my '65 #014xx L76 has one, which I believe is factory, although the '65 TIM&JG makes no allowance for this).

Trans tag 3839602 -- don't have a '64 AIM but it should show there as a table under option M20 & G81 pages. The LIC parts catalog shows this steel tag # as for wide ratio M20 for base and L75 cars.

There should be an trans assembly date code stamped on the machined flat of the lower rear corner of the sidecover (ie P0321). Also, your VIN derivative should appear stamped on the driver side rear vertical of the maincase.

Differential: the 3830303 is correct for '64 (and early '65, as mentioned, and as is on #014xx). Interesting that you are showing a casting date for the rear cover B14 (Feb 1st 1964). Is this on the flange edge between the bolt holes, just forward of the fill plug ? Normally, these C2 diff covers do not have casting dates, but I've heard of one other instance on a "303" case. eg: I also have a '64 diff stamped CF 1-3-64, with a "303" cover that is GM_2 (which is the mold # on the casting line). If you ever have your cover off, you'll see the "303" and the number "5" repeated on the inside. There is NO casting date on either of the "303" covers I have, although that may be related to the mold #. My early '65 car's "303" cover is mould # 3, and it also has NO date, but has the '65-up style plug, with coarse tapered threads, as opposed to the '63-4 fine thread style.

While you were under there, you might have noticed the carrier casting date (on bottom edge under driver side ouput yoke; it's J-18-3 on my CF diff -- sometimes there's a considerable date spread between cast and assembly on this part), and on the passenger side, front middle, the casting # of the carrier (probably 3818753-N). If you're into the diff, there's a whole pile of other numbers on the ring and pinion gears -- lots of fun

[Darwin O.]

Re: Help De-Coding 64 Driveline

Darwin,
Rear cover casting # I think is 3830303, this cover is used in 63-64-and early 65. Sounds like you got all the right stuff for the rear, I don't know Muncie transmission #'s. (yet)

Thanks for the info, the car was sold as an 'all original, unrestored' - other than what's been fixed over the last 44 years... it's nice to get the details sorted out and find out what's been swapped out over the years.

Numbers are good for a '64 Muncie, but the ratios were not coded on the trans until later. If it's out you can tell the ratio by looking at the input shaft, no circumferential rings is a wide ratio, one circumferential ring is a close ratio.

Thanks for the confimation. The tranny is in the car so I can't check the input shaft. My understanding is that the base and L75 engine M20's were wide-ratio, and the L76 and L84's got the close-ratios. That info is not part of the tag or casting numbers, eh? Do the tag and casting numbers give any information beyond year and model? Do you know if the bellhousing and tailshaft housing #'s are correct as well?

Tim your right the rear cover is 3830303, So Darwin disregard the New J/M referernce to its number 3818753 (pape 145) no idea where they got that from. PS Dont forget to put sealer on the pinon splines, more people change a GOOD seal because they think its leaking and its leaking down the splines. Phil 8063

Strange that the new J/M has that discrepency. I'll be sure to double check on the forum if I find any other 'wrong' numbers on my car when my manual arrives. Good advice about spline sealer, I put a smear of hylomar on the splines and on the threads of the nut - as well as sealer on the washer faces. I took it out for a 15 min run yesterday to work the oil around, I'll check for drips today...

Cheers!

[Darwin O.]

Re: Help De-Coding 64 Driveline

Darwin --- to add to what others have said, and items not yet responded to:

383 bellhousing -- These have been reported on later '64s and some early '65s. (my '65 #014xx L76 has one, which I believe is factory, although the '65 TIM&JG makes no allowance for this).

Thanks Wayne, my car is #111804, body tag stamped on Feb 21. I think this puts it on the cusp between early and late...

Trans tag 3839602 -- don't have a '64 AIM but it should show there as a table under option M20 & G81 pages. The LIC parts catalog shows this steel tag # as for wide ratio M20 for base and L75 cars.

There should be an trans assembly date code stamped on the machined flat of the lower rear corner of the sidecover (ie P0321). Also, your VIN derivative should appear stamped on the driver side rear vertical of the maincase.

I checked my AIM, and you're right, D312 shows 3839602 for the wide-ratio (base, L75) M20, and 3839601 for the L76 and L84. I didn't see anything about casting numbers though.

I'll have to get back under there and check for the assembly date and VIN derivative stampings. Very exciting!

Differential: the 3830303 is correct for '64 (and early '65, as mentioned, and as is on #014xx). Interesting that you are showing a casting date for the rear cover B14 (Feb 1st 1964). Is this on the flange edge between the bolt holes, just forward of the fill plug ? Normally, these C2 diff covers do not have casting dates, but I've heard of one other instance on a "303" case. eg: I also have a '64 diff stamped CF 1-3-64, with a "303" cover that is GM_2 (which is the mold # on the casting line). If you ever have your cover off, you'll see the "303" and the number "5" repeated on the inside. There is NO casting date on either of the "303" covers I have, although that may be related to the mold #. My early '65 car's "303" cover is mould # 3, and it also has NO date, but has the '65-up style plug, with coarse tapered threads, as opposed to the '63-4 fine thread style.

While you were under there, you might have noticed the carrier casting date (on bottom edge under driver side ouput yoke; it's J-18-3 on my CF diff -- sometimes there's a considerable date spread between cast and assembly on this part), and on the passenger side, front middle, the casting # of the carrier (probably 3818753-N). If you're into the diff, there's a whole pile of other numbers on the ring and pinion gears -- lots of fun

The B14 casting is exactly where you described, I wonder if all the #5 molds had dates cast into them, or if it was an anomaly? Thanks for the heads-up on the other numbers. Looks like I'll jack the car up to do my post-test drive leak check, and to take down some more numbers. Good Times!

Cheers!

[Joe L.]

Re: Help De-Coding 64 Driveline

Hey Gang!

I was doing the pinion seal on my '64 yesterday, and while I was under there I took down the driveline numbers and have been going through my reference material trying to decode them (still waiting for my 64 judging manual to arrive). Here's what I got:

Bellhousing Casting #: 3840383 (second digit could be a 9, perhaps)

This is the same number that shows up in Noland's book for a L76 engine with an M20, I've got an L75 with an M20. Was this bellhousing used on both?

Tranny Tag: 3839602
Tranny Casting #: 3851325
Tranny Patent #: 3088336
Tranny Tailshaft Housing #: 3846429

Not sure what these mean, does it confirm that it's an M20? Are there casting dates I've missed?

Diff Stamp Pad: CJ 212 64 (3.08 ratio, Feb 12 1964 - 9 days prior to trim tag date)
Diff Cover/Mount Casting #: (3 or 8)8(3 or 8)0303
Diff Cover/Mount Casting Date: B14 (Feb 14th)
Diff Cover/Mount Other Casting: GM5

Anyone know what the correct casting number is for the cover/mount, and what GM5 signifies?

Thanks in advance for any info that you can share.

Cheers!

Darwin-----


GM #3839602 is the correct part number for the wide ratio 4 speed transmission used for your application. It's exactly the one that you should have and, apparently, do have. All the casting numbers you have provided are also correct for your transmission, including the extension housing casting number of 3846429.

I am very confident that the 3840383 bellhousing is correct and, most likely, original to your car. As a matter of fact, my personal opinion is that this bellhousing is the one most likely to have been used on 1964's. It actually surprises me that 3858403's are found on any 64's, especially early cars. But, that's not based on empirical evidence. The '403' bellhousing is a LOT more common than the '383' and was available in SERVICE for a LOT longer. So, hearing of a '403' on a 1964, especially an earlier one, always makes me wonder if the car didn't have its bellhousing replaced somewhere along the way. The '383' and '403' are functionally identical as far as Corvettes go.

The "GM5" is what's known as a pattern number. Differential carriers are a sand casting. In this process, a pattern is used to make the "sand mold". The "sand mold" is a one-time-only sort of thing that is used to make only one piece. Then, it "disintegrates". However, the pattern is used to make many "sand molds", over and over again. For quality control purposes, the patterns have a number associated with them and this number appears on every piece made from a "sand mold" made from a particular pattern.

The above-described process is common to many parts on Corvettes. including cylinder blocks, cylinder heads, intake manifolds, exhaust manifolds, waterpumps, differential carriers, differential carrier covers, rear bearing supports, spindle flanges, brake calipers, master cylinders and others. Pattern numbers will be found on most of these parts and the numbers vary on a random basis. There is no one correct pattern number for any sand cast part on a Corvette (unless only one pattern was used to make the particular part and I don't know of a circumstance like that).

[William C.]

Re: Help De-Coding 64 Driveline

the 3839602 tag would indicate a wide ratio per the '64 Assembly manual.

[Darwin O.]

Re: Help De-Coding 64 Driveline

A big thanks to everyone who's taken the time to reply. Here is the fruit of our labour for my '64 300HP/4-spd Coupe:

Correct bellhousing, tranny casting no, tailshaft housing, tranny ID tag,
and the very exciting correct tranny VIN derivative stamping:



Tranny Assembly Date Stamping (how do I decode this?):



And also, correct diff ratio and carrier assy date stamping, diff cover casting no, and diff cover casting date.

The only thing I couldn't find was the diff carrier casting no and casting date. I found a clock cast into the side of the carrier, but it was really hard to actually see anything with the diff in place. I'm very confident that they are correct, as the stamping jives with the rest of the car and the cover, and that everything else lines up as well. Cool!

These numbers compliment the VIN and trim tags, and the engine pad stamp and casting numbers perfectly, and go a long way to confirming the unmolested nature of this car.









Today I'm a happy camper. A few days ago while changing the seal - that was another story...

Thanks again for all the help, and if anyone knows how to decode the tranny assy date stamping, and has a picture of the carrier numbers I couldn't find, that would be super slick.

Cheers!

[William C.]

Re: Help De-Coding 64 Driveline

The VIN stamping firmly Identifies the trans as original to the car, the '64 code does not include a ratio identifier, but the breakdown is P= Muncie Ind trans plant, Month 02 (Feb) and 10th day, sound prefect for a car in this VIN range.

[Wayne M.]

Re: Help De-Coding 64 Driveline

.. and if anyone ...has a picture of the carrier numbers I couldn't find, that would be super slick.

Cheers!

Sounds like you've got a full hand

here's a pic of the diff carrier showing the castin g # 3818753-N. The casting date should be exactly opposite side to the casting clock, and even closer to the bottom edge. Difficult to see with strut rod bracket still installed, but not impossible when you know where to look.

Note the front carrier mount (to frame) bracket holes. One characteristic is that the most forward holes are tapped for threaded bolts, whereas the rear hole is full bolt diameter. They got rid of the front threaded holes with the later '65 diff # 3876476-N.

[John H.]

Re: Help De-Coding 64 Driveline

Diff Cover/Mount Casting Date: B14 (Feb 14th)

Darwin -

B14 (B 1 4) is February 1, 1964; all your numbers look good to me.

[Darwin O.]

Re: Help De-Coding 64 Driveline

Wayne - thanks for posting that pic. I got the car up on a hoist today, but with the diff in place it's really hard to get at those spots. It wasn't my shop, so I couldn't spend a lot of time with a mirror, rag, light, and camera trying to get a good angle. But, when the diff comes out I'll know where to look.

Thanks again to everyone who helped supply all the numbers and locations, it felt really good confirming the originality of the driveline.

And, my 64 T/M arrived today so I guess I'm better equipped to hunt for this info on my own now...

Cheers!