Is there an easy way to I.D.the aoutomatis trans in this Corvette.Will I see that info on original invoice which I should be getting in a few days?Is this info on a webpage somewhere? Thanks again,Mike Newbee
-
-
Re: 77,L48 auto.trans.
The M40 transmission option will show on the invoice; for a '77 L48, that's a THM350 trans, and the assembly date code will be stamped on the passenger side of the oil pan. -
Re: 77,L48 auto.trans.
Thanks for the response John.My copy of original invoice was faxed to me moments before your reply.Everything you stated was dead on! 7YM40....Turbo Hydramatic...N/CComment
-
Re: Hmmmm....
Mike, beginning in 76, the cost-effective THM350 (M38) was being installed with the economy L48 while the M40 was reserved for L82 duty.
I don't doubt your paperwork but slip underneath and see if the tranny oil pan has a corner missing. On the passenger's side is a metal tag riveted to the tranny housing for an L48 application in 77 will have a AM code in large letters at the top of the tag. Or it might have a CB code for L82.
this one makes me curious...keep us posted.Tom Russo
78 SA NCRS 5 Star Bowtie78 Pace Car L82 M2100 MY/TR/ConvComment
-
Re: Hmmmm....
Corner of oil pan missing means.....?Comment
-
Re: Hmmmm....
Tom, One other note re: type of trans, Factory invoice to dealer in Tallahassee,Fl. dated 6/18/77 shows Vin # for L-48(matches car)and shows7YM40,Turbo Hydramatic Trans*. I don't know if asterisk means anything or not,but no other item on invoice has an asterisk.I have another document which shows several 1977 options,two are:M21 4 speed and M40 automatic.Do you think original buyer opted for the M40 option? Original owner no longer living to ask,I bought car from her nephew who never put it on road.Comment
-
Re: Hmmmm....
What he meant was that the shape of the pan is not a perfect square. It looks as if someone cut cut a corner off of the pan during production. Do a Google search for TH350 and look at the shape of the pan. Very easy to understand the comment once you have seen one pan.
GaryComment
-
Re: Hmmmm....
What I should have asked is which auto.trans has the cut off cornerComment
-
Re: Hmmmm....
Mike-----
I concur with Tom's issue. For 1977, Corvettes equipped with L-48 and auto trans had installed the THM-350 transmission which was known as M-38. Corvettes with L-82 and auto trans had installed the THM-400 transmission also known as M-40. When one ordered an auto trans with L-48, the transmission was a no cost option. When one ordered an auto trans with L-82, one had to pay a cost for the option (since the THM-400 was a more expensive transmission than the THM-350).
HOWEVER, it may be that as far as what was recorded on the build sheet and/or window sticker, only M-40 was used as the designator for BOTH transmissions. Techinically, M-40 was the designator for THM-400. However, it may have had a "dual meaning" for the purposes of build sheet and window sticker. As far as I can tell, M-40 was the only RPO code for automatic transmissions for 1977 Corvettes. That MAY be what the asterisk refers to.
The fact that the M-40 in your case is shown as a no cost option is consistent with the fact that the THM-350 used with L-48 was a no cost option. As far as I know, the THM-400 was not available with the 1977 L-48 regardless of whether one wanted to pay extra for it.
I have attached diagrams of the trans oil pan for both THM-350 and THM-400. With these, you should be easily able to identify the transmission. Also, I believe that the THM-400 used for 1977 Corvettes was identified by the code "CB" on the plate attached to the transmission. I do not know what code was used for THM-350.
In Appreciation of John HinckleyComment
-
Re: Hmmmm....
Mike----
See my diagram in post below.In Appreciation of John HinckleyComment
-
Re: Hmmmm....
Thank you all once again.Great information.Will look tonight. regards,MikeComment
-
You're gonna love this...
I've got a complete set (well sort of) of sales/production documents for a 77 VIN 24998 with L48 and THM 350 and I never caught this before. I've got a build sheet, window sticker and the dealer copy of the invoice.
The build sheets lists RPO M38 and the 3 speed THM 350 tranny.
The window sticker lists an M40 and no charge and an * after the description.
The Dealer copy lists an M40 and no charge.
This indicates build sheet database must have been some derivative or another data base in its own right that was used for production. Sales must have used another and the M40 was listed with no charge but the M38 was installed.
The bottom line...your tranny pan should have the cut corner type drain pan along with the AM code on the tranny metal tag.Tom Russo
78 SA NCRS 5 Star Bowtie78 Pace Car L82 M2100 MY/TR/ConvComment
-
Re: You're gonna love this...
Tom...Bottom line,my car does have the M38 trans.I crawled under car last night to take a look.I also located casting # on back of block,drivers side 3970010. I also scraped away 2 coats of paint on the paint and trim tag and those codes jive with the sales invoice.Comment
Comment