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The performance is not having to be in the right lane and being passed by everyone on the interstate.
Originally Posted by OMF
Do not hesitate to put a 5-speed in.....it will completely change your driving experience for the better. Best change I ever made to my car!
Originally Posted by Richard Daugird
Definitely on my to-do list. Not for fuel economy, but to lower RPM on the freeway and allow some steeper rear gears.
Originally Posted by gkull
Back before OD trannies. I had a 67 RS/SS 350 4 speed Camero. I was commuting a long way to work every day and driving fast. I bought a 2.73 rear end for my 12 bolt. Once that it was rolling it was a fun car. You just had to slip the clutch with the closed ratio 4 speed. both direction every day driving about 90 mph for about 25 miles of my commute unless I felt like blowing the carbon out...
Later with my Vette and 3.55 rear end I hardly ever got passed even on 4500 mile round trips without OD. I just made the motor happy to do higher RPM and it routinely got over 20 mpg cruising at 3000 - 3400 rpm with my 285/17 27.2 inch diam. rear tires.
Originally Posted by Richard Daugird
I hate the high revs on the freeway, especially considering I'm in the slow lane getting passed by everyone else. I know engines can be built that are perfectly happy and efficient at 3500+ RPM for extended periods of time. I have no idea what the "powerband" of my mildly built street 355 is, maybe 3500 is perfect; I still want overdrive. Sure can't hurt. If I decide it sucks cruising at 70 MPH with 4.11 rear gears at 2,200 quiet RPM through the 4" sidepipes, I can always shift back down to 4th gear "caveman" mode. OD is DEFINITELY in my future.
you are lucky OP because now-a-days there are so many ods available to choose that you can get what you want.
I added a few lines to my Transmission ratio spreadsheet to show the differences between a few options.
The first two pairs are examples from my 80 4-speeds 3.07 rear diff. The final pair is @CorvettePassion's 3:55 rear diff. Note that my stock transmission has nearly identical 1,2,3,4 ratios as a TKX, and the M23Z is nearly identical to a Tremec Magnum.
4 speeds works great for most of my fun driving. But sometimes, I like to blast down the highway at 70 mph (highway speed limit for much of Virginia) so I can drive back through the mountains in 2nd and 3rd gear. So, rather than do that at 2700 rpm, why wouldn't I do my highway run at 1700 rpm? I can always choose not to shift into 5th and 6th when I'm on the fun part of the drive.
Has anyone who has installed an overdrive transmission ever NOT considered it an upgrade?
I added a few lines to my Transmission ratio spreadsheet to show the differences between a few options.
The first two pairs are examples from my 80 4-speeds 3.07 rear diff. The final pair is @CorvettePassion's 3:55 rear diff. Note that my stock transmission has nearly identical 1,2,3,4 ratios as a TKX, and the M23Z is nearly identical to a Tremec Magnum.
4 speeds works great for most of my fun driving. But sometimes, I like to blast down the highway at 70 mph (highway speed limit for much of Virginia) so I can drive back through the mountains in 2nd and 3rd gear. So, rather than do that at 2700 rpm, why wouldn't I do my highway run at 1700 rpm? I can always choose not to shift into 5th and 6th when I'm on the fun part of the drive.
Has anyone who has installed an overdrive transmission ever NOT considered it an upgrade?
Your charts show interesting things......like some of these transmissions mimic 1st - 4th gear....and then just add fifth or sixth. I get it. You made your point. I am still not convinced.
And I don't feel like beating this dead horse any longer. I have simply added another perspective to the discussion for people to consider. I think my perspective is unique, and not very common.....but I simply do not want to modernize the car because of the effect it has on how I enjoy and percieve the car...For me, original design is very important to the character of the car. Opening the hood of a C3 and seeing an LS engine in the bay may be considered an "upgrade" to some....but for me, it just turns me off. Same with electric cooling fans, home-made cold air induction systems, turbochargers, back up cameras, late model rear view mirrors, overdrive transmissions, Fiero / late model Corvette seats, LED headlights, Hydroboost, Borgeson, etc etc. Any and all of these "upgrades" ruin the car in my opinion, and if I bought a car with any of these mods, they would be the first thing I removed and sold.
The term "upgrade" means that you are taking something, and making it "better". For me.....a modern, slick shifting, OD transmission is NOT better. It ruins the original character of the car just BECAUSE I know its not a Muncie type 4-speed. AND....then there is:
- cutting and modifying crossmembers
- slick tight shifter mechanism versus the feel of a factory shifter
- possible speedometer cable mods required
- tunnel mods required
- drive shaft mods required
- ugly
- double the cost
But hey......I know I am in the minority. Not the first time, and won't be the last. I typically don't follow the crowd. The crowd often fails to embrace the character of the machine and its meaning to the owner, ...others simply lack the capacity. My love for old cars is based on the fact that they are old cars. And MY old cars are very well built, with high quality versions of the original design......engine, transmission, etc. I don't mess with what Chevy designed when it comes to the rest. In fact, I really do not believe the original design NEEDS improvement......and why I love the car for exactly what it is.
If I wanted a modern Corvette.....I would have saved money by buying one. But I am pretty sure I would be bored with a modern Corvette?? Not sure. Maybe someday I will try one.
Last edited by Torqued Off; 08-05-2022 at 05:27 AM.
Whats the title of this thread? Transmission swap PERFORMANCE difference.... I think the OP who started this thread is more interested in feedback and engineering explanations of the advantages of a modern overdrive transmission, not opinions on why someone would rather a restoration of the original car in pure classic tech form. We all own these old cars for different reasons and the OP stated in the opening post he would like to upgrade this already I think this conversation is best answered by folks with actual experience with this upgrade on thier c3s.
I dont mean to be negative here in any way but I see a trend with multiple threads about multiple upgrades like electric fans, roller cams or even larger rims were someone against these things for their own personal reason starts more or less debating thier choice as the "correct one" when in fact there is no correct choice... But with machinery, technology and engineering in general there are improvements and upgrades and they remain as such whether they are the goal or not.
Jumping into a productive discussion defending personal choices that were never in question in the first place downplaying the advantages or negating them all together to justify those choices to oneself simply doesnt do the conversation any justice. We dont need to all see it the same way. No one tagged anyone into this conversation or called them out to explain their choice. there are DIFFERENT reasons why one choice could be better for one car or owner than another but it still could have nothing to do with the actual mechanical performance which is what this thread was for as I read it.
I totally get why some would want a restored collector type classic... but then I see pics of that persons very beautiful car and cant help but notice they made changes themselves to "Upgrade" things from stock to suite their tastes and it makes me go HMM..
Last edited by augiedoggy; 08-05-2022 at 07:54 AM.
Your charts show interesting things......like some of these transmissions mimic 1st - 4th gear....and then just add fifth or sixth. I get it. You made your point. I am still not convinced.
I'm glad you noticed this time. 😀
Hopefully this is helpful to the OP.
I have a quote for a Tremec Magnum from SST. It will be as much as the car cost me. But still worth it, if it improves the shifter feel. I don't mind the heavy clutch, but I've driven a LOT of manuals, and most felt better than what's in my car. The 1-4 skip shift in the T56 GTO ruined it for me, but it wasn't Tremec's fault, and that won't be a problem in the Vette.
Hopefully I can see SST's demo at Carlisle and decide.
I have a 4.11 rearend and 5 speed now being used as my daily driver. Really fun car to drive. Cost effective, better mpg, not at all 🤪
but the rumble of the motor and the body shaking even with 1200 rpm idle gets lots of attention
The ultimate build would need to be something like a t56 magnum 6 speed with a 4.56 or 4.88 rearend. Close up the gear spacing and make the. 50 sixth gear nice for the highway.
But hey......I know I am in the minority. Not the first time, and won't be the last. I typically don't follow the crowd. The crowd often fails to embrace the character of the machine and its meaning to the owner, ...others simply lack the capacity. My love for old cars is based on the fact that they are old cars. And MY old cars are very well built, with high quality versions of the original design......engine, transmission, etc. I don't mess with what Chevy designed when it comes to the rest. In fact, I really do not believe the original design NEEDS improvement......and why I love the car for exactly what it is.
If I wanted a modern Corvette.....I would have saved money by buying one. But I am pretty sure I would be bored with a modern Corvette?? Not sure. Maybe someday I will try one.
I understand where your head is at, man. I kind of agree with you, But maybe don't feel it as strongly as you do, but I get it. I don't know how much you know about firearms, but I have an M1 Garand rifle. People tell me I should put a scope on it, or a red dot sight, or a more modern polymer replacement stock, or any number of new-fangled doo-dads and gee-gaws on it. Nope! I like it just exactly the way it was when it was built in June of 1944! It's The Original Classic American Muscle Rifle, and I like it just the way it was when my grandads carried 'em back in The Big One! Speaking of my grandad, one of 'em used to say, "It would be an awfully boring world if we all liked the same things, Scotty." So, you do you, brother!
I have a 4.11 rearend and 5 speed now being used as my daily driver. Really fun car to drive. Cost effective, better mpg, not at all 🤪
but the rumble of the motor and the body shaking even with 1200 rpm idle gets lots of attention
The ultimate build would need to be something like a t56 magnum 6 speed with a 4.56 or 4.88 rearend. Close up the gear spacing and make the. 50 sixth gear nice for the highway.
But what would your MPG be in that same setup with just the 4 speed?
I understand where your head is at, man. I kind of agree with you, But maybe don't feel it as strongly as you do, but I get it. I don't know how much you know about firearms, but I have an M1 Garand rifle. People tell me I should put a scope on it, or a red dot sight, or a more modern polymer replacement stock, or any number of new-fangled doo-dads and gee-gaws on it. Nope! I like it just exactly the way it was when it was built in June of 1944! It's The Original Classic American Muscle Rifle, and I like it just the way it was when my grandads carried 'em back in The Big One! Speaking of my grandad, one of 'em used to say, "It would be an awfully boring world if we all liked the same things, Scotty." So, you do you, brother!
Scotty
Good example.
I have a couple Mosin Nagants and I also chose to keep the pristine original example just that. I hunted with it once but didnt like having it in the woods and rain since It had a lot off crannies for rust to accumulate and well the folding bayonet was not so practical for hunting. But after a couple of years, like the car, I found an old cold war non matching serial numbered mess of a gun (with good rifling in the bore) which I cut down the long m91 barrel recrowned I added a turned down machined bolt walnut stock I modified the trigger and addded a scope and refinished the once pitted and painted black barrel I bought so the gun is a fantasic and more practical Deer hunting rifle I actually enjoy using.... The last deer I got with it no longer had an intact heart (or any heart Icould find) and dropped in its tracks with a perfect shot. The pristine M44 carbine? not so much... Its cool to look at but it just sits in my gun cabinet waiting to be passed on to its next caretaker some day. Maybe it will be worth something to another collect some day.. maybe not, but im getting the most use and enjoyment now out of the gun modified for my intended use.
Last edited by augiedoggy; 08-05-2022 at 10:35 AM.
But what would your MPG be in that same setup with just the 4 speed?
Like I said in an above post. If you got 2 more MPG with an OD tranny it would take a long time to recoup $5000 in cost.
Second of all I don't think that any Muncie m-20 or 21 would last one day. Modded m22 might last for a short period of time before the case breaks. I wouldn't ever buy one the TQ ratings are very low.
I have a quote for a Tremec Magnum from SST. It will be as much as the car cost me. But still worth it, if it improves the shifter feel. I don't mind the heavy clutch,
If you go with a Twin disc you loose the heavy clutch. Feels like a C5 / C6 corvette when shifting.
My 78 T56 Magnum started with a single disc and after 30 days I changed to a twin-disc and would never again recommend a single disc for a T56 Swap.
Like I said in an above post. If you got 2 more MPG with an OD tranny it would take a long time to recoup $5000 in cost.
Second of all I don't think that any Muncie m-20 or 21 would last one day. Modded m22 might last for a short period of time before the case breaks. I wouldn't ever buy one the TQ ratings are very low.
is it really 2mpg though? on my cars I notice a lot more than 2mpg when the rpms drop 700-900 rpms... Not doubting you but I think for a typical mild performance sbc the gains would be higher than 2mpg. I got 27mpg on my old crossfire car in overdrive... I realize it had a small cam and throttle body injection but... even my ram diesel mpg average jumps about 7mpg in overdrive.
anyone who has swapped their 4spd transmission with a 5 or 6spd, what was the fuel economy like before and after on any C3.
I am going to purchase my first corvette and have had my eyes on a 1978 stingray with a 4spd manual trans and I would like to upgrade it.
if someone could get back with me, that would be great!
To answer your question direct or almost direct, I didn't have a 4spd manual.
My Factory 78 corvette TH350 auto (3.08 rear diff) at best would get ~18 MPG ~ 15 US MPG
Engine change from Factory 350 to ZZ383 ~ 20 MPG ~ 16.67 US MPG This was due to Computer controlled timing curve and tuned carb using AFR Data logger.
Change to T56 Mag 6 speed with .63 6th gear. 27.8 MPG (23.4 MPH US)
Now just to compare I get ~ 8 MPG ( 6.6 MPG US) when driving on the track road course.
The 6 speed T56 Magnum choice was due to the torque rating of the transmission to support the ZZ383 & LS3 engines. Great shifting feel at the track (up & down shifting) better engine RPM driving everywhere.
The install for my 78 was simple except for adding the clutch pedal. Only mod required was to cut the tunnel for the shifter. Everything else used factory mounts. (worked because with a auto car the trans cross member is removeable)
Last edited by cagotzmann; 08-05-2022 at 04:45 PM.
16.67 US MPG This was due to Computer controlled timing curve and tuned carb using AFR Data logger. Change to T56 Mag 6 speed with .63 6th gear. (23.4 MPH US)
Now that is a nice gain! It also shows that going to modern LS motors might be just as cost effective as a OD tranny if you have something like a 3.08 rear end.
People have ask me at car events what kind of MPG does a 670 HP 434 get. My best answer is, "Time is Money" I can get there is less time than a Honda Fit!
To answer your question direct or almost direct, I didn't have a 4spd manual.
My Factory 78 corvette TH350 auto (3.08 rear diff) at best would get ~18 MPG ~ 15 US MPG
Engine change from Factory 350 to ZZ383 ~ 20 MPG ~ 16.67 US MPG This was due to Computer controlled timing curve and tuned carb using AFR Data logger.
Change to T56 Mag 6 speed with .63 6th gear. 27.8 MPG (23.4 MPH US)
Now just to compare I get ~ 8 MPG ( 6.6 MPG US) when driving on the track road course.
The 6 speed T56 Magnum choice was due to the torque rating of the transmission to support the ZZ383 & LS3 engines. Great shifting feel at the track (up & down shifting) better engine RPM driving everywhere.
The install for my 78 was simple except for adding the clutch pedal. Only mod required was to cut the tunnel for the shifter. Everything else used factory mounts. (worked because with a auto car the trans cross member is removeable)
Theres the 7mpg ballpark I would expect to see even with a carbed sbc
Whats the title of this thread? Transmission swap PERFORMANCE difference.... I think the OP who started this thread is more interested in feedback and engineering explanations of the advantages of a modern overdrive transmission, not opinions on why someone would rather a restoration of the original car in pure classic tech form. We all own these old cars for different reasons and the OP stated in the opening post he would like to upgrade this already I think this conversation is best answered by folks with actual experience with this upgrade on thier c3s.
I dont mean to be negative here in any way but I see a trend with multiple threads about multiple upgrades like electric fans, roller cams or even larger rims were someone against these things for their own personal reason starts more or less debating thier choice as the "correct one" when in fact there is no correct choice... But with machinery, technology and engineering in general there are improvements and upgrades and they remain as such whether they are the goal or not.
Jumping into a productive discussion defending personal choices that were never in question in the first place downplaying the advantages or negating them all together to justify those choices to oneself simply doesnt do the conversation any justice. We dont need to all see it the same way. No one tagged anyone into this conversation or called them out to explain their choice. there are DIFFERENT reasons why one choice could be better for one car or owner than another but it still could have nothing to do with the actual mechanical performance which is what this thread was for as I read it.
I totally get why some would want a restored collector type classic... but then I see pics of that persons very beautiful car and cant help but notice they made changes themselves to "Upgrade" things from stock to suite their tastes and it makes me go HMM..
Its called a FORUM.....and I think it is relevant to comment on transmission choices,....as well as PERFORMANCE versions of the original 4 speed. But, I guess you don't want to hear it....so don't read it. I will move....so you can all discuss what you want without alternative ideas.
As for the other things you quality as "upgrades".....yeah we have had those conversations as well....electic fans, Borgeson, etc. Problem is the crowd is NEVER satisfied unless they consider these things "better".....when all they are is different. IT HAS TO BE BETTER. IT MUST BE BETTER. I got it.
But....again...I will sign off this thread and let you all talk about your OD transmissions.
To answer the original poster.
YES. A 5 or 6 Speed transmission with overdrive is a wonderful UPGRADE. Your car will be a lot more pleasant all the way around. If and/or when you get the opportunity, then GO for it.
Originally Posted by C3Garner1
anyone who has swapped their 4spd transmission with a 5 or 6spd, what was the fuel economy like before and after on any C3.
I am going to purchase my first corvette and have had my eyes on a 1978 stingray with a 4spd manual trans and I would like to upgrade it.
if someone could get back with me, that would be great!
- cutting and modifying crossmembers
- slick tight shifter mechanism versus the feel of a factory shifter
- possible speedometer cable mods required
- tunnel mods required
- drive shaft mods required
- ugly
- double the cost
.
Not trying to change anyone's mind, just need to clarify a few things... I've had a TKO600 for 16 years.
- cutting and modifying crossmembers
Not Required
- slick tight shifter mechanism versus the feel of a factory shifter
I don't see much difference
- possible speedometer cable mods required
No Mods, just install the correct speedo cable
- tunnel mods required
Not Required
- drive shaft mods required New Driveshaft
- ugly
Ahhh, have not seen anyone "slither" under my car lately to check out the looks of my transmission.
- double the cost Can't take it with you !
My '70 is close to 100% original, including paint & the owner. At car shows, etc., no one knows the transmission is a 5-speed.
Three factors for me in choosing a TKO600 5- speed
- Better 1 st gear, 2:20 vs 2:87
- With side exhaust and 3:70 gears, highway speed was noisy. With 5-speed, drop 1K rpm in 5th, dramatic drop in exhaust noise.
- Improved MPG ( In imperial gallons - gained 10 mpg) If I live to be 150 years old, improved mileage will pay for the transmission.
08-04-2022, 06:00 PM
