L-72 bellhousing transmisssion

[Jerry weidner]

The L-72 I found has a the vin# stamped on the tranny so I know its original, it also has a drain plug on the bottom but i cannot prove that it was not added. My question is the car has bell housing 3840383 , transmission tag on the tranny is still there and is 3880853, rear end ratio is 3:70 it is an early 66 car. I saw on the archives before someone with this exact combo but cannot find the thread anymore. Could this have been the correct bellhousing and If so what starter would have been used?

Thanks,
Jerry

[Joe L.]

Re: L-72 bellhousing transmisssion

Jerry----

I strongly doubt that the 3840383 bellhousing is original to the car, but I won't rule it out if it's a VERY early 1966. The bellhousing you describe and the clutch assembly used with it are the 1965 L-78 configuration. I suppose it's possible that some VERY early L-72's used this, too. I strongly doubt it, but I wouldn't rule it out completely.

Another "discrepency" is the 3840383 bellhousing, itself. While this bellhousing would work perfectly on a functional basis and the engine plant could have used it, the use of that bellhousing was pretty much over by the time your car was built. Most, if not all, 1965 Corvettes with L-78 used the successor bellhousing, GM #3858403. So, your car not only has a flywheel/clutch set-up I would not expect on your car (inferred by the bellhousing), but it also has a bellhousing part number that I wouldn't even expect to find on a 1965 L-78.

With either the '383' or the '403' bellhousings, you would need a starter with an aluminum nose and "long" and "short" starter bolt configuration. I would expect starter GM #1107352.

By the way, the greatest liklihood of finding an original '383' or '403' bellhosuings (and, consequently, a 12-3/4" flywheel/10-1/2" clutch combination) on a 1966 big block would be on those VERY few made with M-22 transmission. Your transmission number rules that out, since the GM #3880853 is an M-21.

[Jerry weidner]

Re: L-72 bellhousing transmisssion

Joe,

The transmission has the drain plug for an m22? Is it correct that the only the M22 has the drain plug? also I thought I read that the transmission tag of 853 did not necessarly call out specifically the M-21 but could have been the M-22 with a 3:70 rear end ratio? The car use to be a drag car How do I tell if it is a M-22 transmission? The drain plud looks original but I cannot tell? Also as I take it apart over the winter how do I tell a 12-3/4" flywheel and if its a 10-1/2" clutch.

Jerry

[Jerry weidner]

Re: L-72 bellhousing transmisssion

I found this in the archives,
Think of the tranny tags as only being indirectly related to the engine option.

Rather, the tag is to identify if the trans is wide or close ratio, and,if close ratio, is the drive gear on the mainshaft tail suited for the low numerical differential ratios (3.08, 3.36, 3.55) or the higher ones (3.70, 4.11) [Let's ignore the 4.56 for this discussion].

So there are 3 possibilities [let's also ignore the M22 possibilities]; base engines and wide ratio L79's should use the 3870354; L79's with the close ratio, and L72's with the mandatory close ratio, but 3.70 or 4.11 rear should use 3880853, and L72's with the 3.55 "general purpose" or lower numerical ratios shold use 3880855. L36's with the wide ratio should use the "354". Were L36's available with the close ratio ? if so, same trans #'s as for L72's, depending if high and low numerical rears.

So I guess my question remains could I still have the original set up if it was an m22 with 383 bellhousing and 3:70 rear end?It was an early oct car.

Regards,
Jerry

[Mark #28455]

anything is POSSIBLE, but Bubba is more likely *NM*

[Jerry weidner]

Re: anything is POSSIBLE, but Bubba is more likely

Could be Bubba, But it sure looks original, I also saw this exact same setup in the archives, I just have not found it yet, on an early L72 from another member.

Jerry

[Joe L.]

Re: L-72 bellhousing transmisssion

Jerry-----

GM #3880853 is the part number used for M-21 transmissions used for 66-67 Corvettes with 427 and 3.70:1 or 4.11:1 rear gear ratios. It is NOT a part number ever used for a HD close ratio transmission (i.e. M-22). So, unless someone "swapped" this tag from another transmission onto an M-22, the transmission is an M-21. To absolutely confirm one way or the other, all you need to do is to remove the side cover and not the helix angle of the gears. I think you'd be wasting your time, though. First of all, the part number tag pretty much ensures what it is. Secondly, I don't think that any of the few M-22s that were installed for 1966 were installed in cars that early.

If a drain plug is added to a non-original-drain plug case, it can look just like it's original. Unless somebody really screws up, this is how it should look.

If you have the '383' bellhousing, then you MUST have the 12-3/4" flywheel and 10-1/2" clutch. The only other possibility would be the 14" flywheel and 11" clutch. Those won't fit within the '383' bellhousing. So, just be knowing the bellhousing part number, you pretty much know what has to be inside.

[Jerry weidner]

Re: L-72 bellhousing transmisssion

Thanks Joe, I am sure the plug must have been added at some time?

Jerry

[Joe L.]

Re: L-72 bellhousing transmisssion

Jerry-----

I would expect so. Also, there's always the possibility that a drain plug case was originally installed. There was nothing to stop the folks in Muncie from using such a case if they had some around that they needed to "get rid of" or because of a shortage of non-drain plug cases. Unfortunately, you'd probably never be able to convince a judge of that without some sort of documentation (which you'd never be able to come up with for something like this).