1977 l82
Instructor
Joined: Nov 2013
Posts: 220
Likes: 17
From: Pasadena MD
Instructor
Joined: Feb 2016
Posts: 182
Likes: 27
From: Somerville Alabama
Seems like that would be close for 2nd gear if it has a 3.08 rear end.
I don't know what the 4.11 RPM @ 65 MPH would be for 3rd gear but maybe that's also close.
Seeing now what widowmaker221 said, info I collected before says
3.55: 2830 @ 65
My car, a '77 L48 with TH350 Auto., does about 2700 RPM @ 65. It apparently has a 3.36 rear end, the original steel type was replaced with aluminum 1980-82 "batwing" type.
I don't know what the 4.11 RPM @ 65 MPH would be for 3rd gear but maybe that's also close.
Seeing now what widowmaker221 said, info I collected before says
3.55: 2830 @ 65
My car, a '77 L48 with TH350 Auto., does about 2700 RPM @ 65. It apparently has a 3.36 rear end, the original steel type was replaced with aluminum 1980-82 "batwing" type.
Last edited by LongRoadHome; Oct 4, 2016 at 04:12 PM.
Racer
Joined: Sep 2001
Posts: 352
Likes: 51
From: Austin TX
My 78 L82 (now a 350 crate) runs same 3500 RPM at 65. I've got a 3.70 rear. I thought it seemed high when I first drove it, but it appears to be inline.
It's a 4 speed, OD would sure be nice for better road manners on longer highway trips.
It's a 4 speed, OD would sure be nice for better road manners on longer highway trips.
Le Mans Master
Joined: Jun 2013
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From: Colorado
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My L-82 close ration 4 speed runs 3500 at 75 mph with a 3.70 rear, so I'd say your's is normal.
Burning Brakes
Joined: Dec 2005
Posts: 1,164
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From: Pawleys Island, SC
Instructor
Joined: Feb 2016
Posts: 182
Likes: 27
From: Somerville Alabama
Reading back here no one mentioned possibility of speedometer being inaccurate. Mine is off by about -3 MPH apparently from changed rear end gear.
I just got back into this stuff this year, not something a paid much attention to when I was a teenager and much less (not at all) thereafter. So I'm really way out of the loop on things.
I'm not understanding the reason for the widely varying numbers for RPM for similar gearing. The 4-speed manual has 1:1 4th gear equal to TH350 3rd, or is there another difference I wasn't aware of? Besides Automatic torque converter "slippage".
A while ago I was using the following web pages to help understand what was available on these cars:
http://corvettec3.ca/trans.htm
http://corvettec3.ca/axle.htm
Home buttons there go to all other info about the C3 cars.
I just got back into this stuff this year, not something a paid much attention to when I was a teenager and much less (not at all) thereafter. So I'm really way out of the loop on things.
I'm not understanding the reason for the widely varying numbers for RPM for similar gearing. The 4-speed manual has 1:1 4th gear equal to TH350 3rd, or is there another difference I wasn't aware of? Besides Automatic torque converter "slippage".
A while ago I was using the following web pages to help understand what was available on these cars:
http://corvettec3.ca/trans.htm
http://corvettec3.ca/axle.htm
Home buttons there go to all other info about the C3 cars.
Thread Starter
Racer
Joined: Oct 2016
Posts: 372
Likes: 9
From: Sorrento Louisiana
Varifying speed/RPM
Reading back here no one mentioned possibility of speedometer being inaccurate. Mine is off by about -3 MPH apparently from changed rear end gear.
I just got back into this stuff this year, not something a paid much attention to when I was a teenager and much less (not at all) thereafter. So I'm really way out of the loop on things.
I'm not understanding the reason for the widely varying numbers for RPM for similar gearing. The 4-speed manual has 1:1 4th gear equal to TH350 3rd, or is there another difference I wasn't aware of? Besides Automatic torque converter "slippage".
A while ago I was using the following web pages to help understand what was available on these cars:
http://corvettec3.ca/trans.htm
http://corvettec3.ca/axle.htm
Home buttons there go to all other info about the C3 cars.
I just got back into this stuff this year, not something a paid much attention to when I was a teenager and much less (not at all) thereafter. So I'm really way out of the loop on things.
I'm not understanding the reason for the widely varying numbers for RPM for similar gearing. The 4-speed manual has 1:1 4th gear equal to TH350 3rd, or is there another difference I wasn't aware of? Besides Automatic torque converter "slippage".
A while ago I was using the following web pages to help understand what was available on these cars:
http://corvettec3.ca/trans.htm
http://corvettec3.ca/axle.htm
Home buttons there go to all other info about the C3 cars.
I had my wife follow behind me in her car. When I reached 3500 RPM I varified the speed. I reacently varified I have a Tubo 350 transmision. I have a lot of hydrolic stearing and engine oil leaks so I am still having trouble varifing the gears on the rear end. Im glad to know at least there is nothing drasticly wrong with the drive train.
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Melting Slicks
Joined: Sep 2004
Posts: 3,226
Likes: 668
From: Northeast
In 77 if you ordered a L82, auto, the standard rear was 3.55. So unless you feel someone changed it that is what you have.
I think the tach is off. When I went on a dyno the operator said my tach was off @200rpm. At 70 it was reading close to 3500. See the dyno sheet showing @3300 for my 3.70 rear.
I think the tach is off. When I went on a dyno the operator said my tach was off @200rpm. At 70 it was reading close to 3500. See the dyno sheet showing @3300 for my 3.70 rear.
Thread Starter
Racer
Joined: Oct 2016
Posts: 372
Likes: 9
From: Sorrento Louisiana
Feeling out the car!!!
In 77 if you ordered a L82, auto, the standard rear was 3.55. So unless you feel someone changed it that is what you have.
I think the tach is off. When I went on a dyno the operator said my tach was off @200rpm. At 70 it was reading close to 3500. See the dyno sheet showing @3300 for my 3.70 rear.
I think the tach is off. When I went on a dyno the operator said my tach was off @200rpm. At 70 it was reading close to 3500. See the dyno sheet showing @3300 for my 3.70 rear.
Le Mans Master
Joined: Oct 2005
Posts: 6,247
Likes: 471
From: Glen Allen, VA
I drive mine for hours at a time btwn 3500 and 4000 rpm on every road trip. I've been doing this for 10 years so far and no problems. Yes, I'd love to have an overdrive 5 speed in mine, but it's not in the budget at the moment.
Thread Starter
Racer
Joined: Oct 2016
Posts: 372
Likes: 9
From: Sorrento Louisiana
4000 rpm
Seems like every time I try to run it at 4000 RPM something goes wrong. First the Alternator belt broke. Replaced that. Next the alternator started sparking. Replaced that. Next it would start smoking from under the car. That's from oil leaks but it does not smoke at 3500 RPM. Working on the leaks this weekend. Maybe one day a 5 speed!!!!