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I recently have seen two LT1 cars offered for sale with M20 wide ratio four speeds. Am I missing something. Was this option available via COPO? I thought that after 1969 no M20 option was available and as far as LT1's only the M21 or M22 was the choice.
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Re: LT1 transmission options
I am not aware of any transmission restriction on LT1 except M22 in some years. Where did you get your information?Terry -
Re: LT1 transmission options
I ask because a M20 is not listed as an option after 1969 in any publication I can find including the Corvette Black Book.Comment
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Re: LT1 transmission options
I also found several archive posts that also state that only the M21 or M22 were avaiable for the LT1.Comment
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M20
is the code for the standard wide ratio four speed for all years. It's listed as an option in '69 and prior because the 3 speed was the base transmission.
In '70 and up it's what you got as standard equipment which is why it's no longer listed as an option.Comment
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Re: LT1 transmission options
Mike hit on why M20 is not listed as an option for 1970 and up. There are a fair number of M20 factory equipped LT1s. Just that most folks opted for the no-cost close ratio M21.
The only way to get an M22 in 1970 and 1972 was to get the ZR1 package. I know we will get some debate on it, but for 1971 the evidence is a little less clear on M22 installation.TerryComment
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Re: LT1 transmission options
Thanks guys I stand corrected.Comment
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The NCRS Spec. Guides...
...show all the available powertrain combinations for all years.
DukeComment
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Re: The NCRS Spec. Guides...
Duke, I don't have that one so what is your answer re: the question?Comment
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Re: The NCRS Spec. Guides...
You could order LT-1 with either a wide ratio or close ratio four-speed. The wide ratio was the default on all engines except LS-6 which is why M-20 is not listed as an available option in those years, but it could be overridden with M-21, and LS-6 would have been an automatic M-21.
DukeComment
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Re: LT1 transmission options
Rob if there were two LT-1's for sale and one was a M20 and the other a M21 being the only difference I would buy the the LT-1 with the M20 if I was going to buy it to drive. The first gear take offs would be easier. My wife drove our orignal owner 68 327/350 M21 3:70 a lot until 1973. I changed replaced the the clutch in 1973 because it was slipping. One side of the clutch disc was almost gone and was worn abnormally worn. Lot of clutch slipping by someone. The replacement clutch is still functional.Comment
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Re: LT1 transmission options
Depends on both the transmission and axle. With a WR the typical standard axle was 3.36 and 3.70 with CR.
2.54 x 3.36 = 8.53
2.20 x 3.70 = 8.14
...only a 5 percent difference, but IMO the words "female" and "clutch" are mutally exclusive, but then I've know plenty of guys who were ham-footed when it came to operating a clutch.
I drove a L-76/CR/3.08 around Seattle for 5 years and 60K miles. I decided to do a pre-emptive change just before I graduated from college because I had a good opportunity to change it at that time. (I actually did the work on the U of W campus in the ME building!) It was in good shape and probably would have lasted until I pulled the engine for rebuild at 115K.
DukeComment
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Interesting clutch design...
The GM coaches I drove (V6-71 two-stroke cycle diesel with a Roots scavenging blower) in the summer of '67 had an interesting design feature - a lockout that prevented the throttle from opening until the clutch was engaged. You could floor the throttle in first with the clutch disengaged at a dead stop and engine speed would not increase.
So you just slowly engaged the clutch and once the pedal was up it would take throttle and the engine would begin to rev up.
I've always used a similar technique in my cars - engage the clutch without exceeding idle speed (normal driving, but some situations required a more aggressive start). It takes a little practice to pickup the technique, but it will yield very long clutch life. I also double clutch all downshifts which eases the load on the synchronizers and clutch.
The technique is a little tricky to implement on a vintage engine, but modern FI cars with idle speed control is a piece of cake because the idle speed control will add a little throttle when revs first drop with initial engagement, but just enough to maintain programmed idle speed.
DukeComment
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