C3 transmission swap for overdrive. Advice from a mechanic.
10-17-2016, 08:38 PM
#1
Advanced
Thread Starter
C3 transmission swap for overdrive. Advice from a mechanic.
Hey ya'll.
Just wanted to pass along my experience in case anyone wants the information in the future but doesn't happen along a great mechanic like I have.
I decided to look for a transmission to swap into my 74 L82 in order to gain an overdrive. My goal would be to lower rpm at highway speed while not losing low speed 'fun factor'. I've read all the forums and do it yourself guides on 200R4 vs 700R4 swaps. I have a stock engine and decided to find a 200R4 because I am not making a ton of horsepower and I have a 4.11 rear diff (which allegedly lines up better with the 4.11).
I found a shop in my area that specifically works with performance classic cars and vettes and gave the guy a call. I told him that I had been shopping the transmissions listed above. He was receptive to what I had planned (in terms of goals) but then offered feedback. Yes the 200R4 would be a great transmission now, but if I ever decided to build horsepower into the engine then I would end up needing another swap. He recommended an 4L60E although he told me the price would be twice as much. As an alternative he agreed that the 700R4 would go into my car with minimal modification for a good price and that it should be paired with a 3.55 or 3.08 rear diff change over if I wanted to really have a good road car and had no need of racing application. Overall he has been in business for over 20 years and has built many corvettes for various purposes, but alleges that no one is ever truly happy with a 200R4 or 700R4.
He pointed me to his transmission source who I called next.
Upon calling the transmission guy I was initially told I would not buy a 200 or 700 transmission from his shop. Some numbers included the torque rating which on the TH400 I have now is 80 and the torque rating on the 200 and 700 is 60, therefore they are substandard transmissions. He then explained that over the years he has sold and allowed many of these remanufactured transmissions to be placed in street and performance applications. I was told that they would never shift correctly, however, and that in order to get their internals to shift in a manner that would be pleasing it would put the internal pressures at levels that result in fast breakdown of the components. These transmissions would never mate to my throttle correctly and would always seek internals on my motor that don't exist. Lastly, 4th gear lockouts are finicky and he said that most people end up with nonsensical 1st and 2nd gears and then issues going into 3rd or 4th gear. He pleaded that I listen to quotes for a 4L60E and so I did.
Maybe I turned a blind eye to the electronic transmissions because I thought they were too expensive when I began my research, but I have to say this has been eye opening. Both of these guys could have taken my money and dropped either of those transmissions in my car. Neither of them want to allow it and they have both pushed for a 4L60E if I must have an overdrive. It was also highly recommended that I simply swap out my 4.11 rear end for a 3.08 and keep the TH400. I think I'm going to go that route.
I know this subject is beating a dead horse, but I wanted to put my experience out there for others looking to read as much as possible.
Just wanted to pass along my experience in case anyone wants the information in the future but doesn't happen along a great mechanic like I have.
I decided to look for a transmission to swap into my 74 L82 in order to gain an overdrive. My goal would be to lower rpm at highway speed while not losing low speed 'fun factor'. I've read all the forums and do it yourself guides on 200R4 vs 700R4 swaps. I have a stock engine and decided to find a 200R4 because I am not making a ton of horsepower and I have a 4.11 rear diff (which allegedly lines up better with the 4.11).
I found a shop in my area that specifically works with performance classic cars and vettes and gave the guy a call. I told him that I had been shopping the transmissions listed above. He was receptive to what I had planned (in terms of goals) but then offered feedback. Yes the 200R4 would be a great transmission now, but if I ever decided to build horsepower into the engine then I would end up needing another swap. He recommended an 4L60E although he told me the price would be twice as much. As an alternative he agreed that the 700R4 would go into my car with minimal modification for a good price and that it should be paired with a 3.55 or 3.08 rear diff change over if I wanted to really have a good road car and had no need of racing application. Overall he has been in business for over 20 years and has built many corvettes for various purposes, but alleges that no one is ever truly happy with a 200R4 or 700R4.
He pointed me to his transmission source who I called next.
Upon calling the transmission guy I was initially told I would not buy a 200 or 700 transmission from his shop. Some numbers included the torque rating which on the TH400 I have now is 80 and the torque rating on the 200 and 700 is 60, therefore they are substandard transmissions. He then explained that over the years he has sold and allowed many of these remanufactured transmissions to be placed in street and performance applications. I was told that they would never shift correctly, however, and that in order to get their internals to shift in a manner that would be pleasing it would put the internal pressures at levels that result in fast breakdown of the components. These transmissions would never mate to my throttle correctly and would always seek internals on my motor that don't exist. Lastly, 4th gear lockouts are finicky and he said that most people end up with nonsensical 1st and 2nd gears and then issues going into 3rd or 4th gear. He pleaded that I listen to quotes for a 4L60E and so I did.
Maybe I turned a blind eye to the electronic transmissions because I thought they were too expensive when I began my research, but I have to say this has been eye opening. Both of these guys could have taken my money and dropped either of those transmissions in my car. Neither of them want to allow it and they have both pushed for a 4L60E if I must have an overdrive. It was also highly recommended that I simply swap out my 4.11 rear end for a 3.08 and keep the TH400. I think I'm going to go that route.
I know this subject is beating a dead horse, but I wanted to put my experience out there for others looking to read as much as possible.
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e009061 (08-04-2018)
10-18-2016, 09:27 AM
#2
Drifting
Member Since: Oct 2005
Location: Forth Worth TX
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It's your car and your money. Not sure how much you plan on driving your car or what the cost of switching to a 5spd(or OD) will be, but here's a quick and simple comparison of 4 vs. 5 speed.
4spd - 15mpg x 1k miles =66.6 gallons of gas x $2.00 per gallon = $133 to drive 1000 miles at highway speeds.
5spd - 20mpg x 1k miles = 50 gallons of gas x $2.00 per gallon = $100 to drive 1000 miles at highway speeds.
(An increase from 15mpg to 20mpg would be a 33% increase in fuel economy. Your results will most likely be less.)
A $33 difference for every 1000 miles at highway speeds(4th gear vs. 5th gear). When you drive around town and aren't in 5th gear there's virtually no savings.
If you're driving 20k miles per year, great. If you drive 1k miles per year....well?
4spd - 15mpg x 1k miles =66.6 gallons of gas x $2.00 per gallon = $133 to drive 1000 miles at highway speeds.
5spd - 20mpg x 1k miles = 50 gallons of gas x $2.00 per gallon = $100 to drive 1000 miles at highway speeds.
(An increase from 15mpg to 20mpg would be a 33% increase in fuel economy. Your results will most likely be less.)
A $33 difference for every 1000 miles at highway speeds(4th gear vs. 5th gear). When you drive around town and aren't in 5th gear there's virtually no savings.
If you're driving 20k miles per year, great. If you drive 1k miles per year....well?
10-18-2016, 07:20 PM
#3
Advanced
Thread Starter
It's your car and your money. Not sure how much you plan on driving your car or what the cost of switching to a 5spd(or OD) will be, but here's a quick and simple comparison of 4 vs. 5 speed.
4spd - 15mpg x 1k miles =66.6 gallons of gas x $2.00 per gallon = $133 to drive 1000 miles at highway speeds.
5spd - 20mpg x 1k miles = 50 gallons of gas x $2.00 per gallon = $100 to drive 1000 miles at highway speeds.
(An increase from 15mpg to 20mpg would be a 33% increase in fuel economy. Your results will most likely be less.)
A $33 difference for every 1000 miles at highway speeds(4th gear vs. 5th gear). When you drive around town and aren't in 5th gear there's virtually no savings.
If you're driving 20k miles per year, great. If you drive 1k miles per year....well?
4spd - 15mpg x 1k miles =66.6 gallons of gas x $2.00 per gallon = $133 to drive 1000 miles at highway speeds.
5spd - 20mpg x 1k miles = 50 gallons of gas x $2.00 per gallon = $100 to drive 1000 miles at highway speeds.
(An increase from 15mpg to 20mpg would be a 33% increase in fuel economy. Your results will most likely be less.)
A $33 difference for every 1000 miles at highway speeds(4th gear vs. 5th gear). When you drive around town and aren't in 5th gear there's virtually no savings.
If you're driving 20k miles per year, great. If you drive 1k miles per year....well?
10-18-2016, 09:44 PM
#4
Drifting
Since you're considering spending significant bucks on a trans, why not change over to a manual transmission and increase your fun factor ten fold. You could go with an inexpensive T5 or go with a wide ratio 4 speed and a set of 3.08's, and have the best of both worlds.
10-18-2016, 10:09 PM
#5
Advanced
Thread Starter
Since you're considering spending significant bucks on a trans, why not change over to a manual transmission and increase your fun factor ten fold. You could go with an inexpensive T5 or go with a wide ratio 4 speed and a set of 3.08's, and have the best of both worlds.
Edit: apparently the wide ratio 4 speed has a 4th gear ratio of 1.0 which is the same as the 3rd gear on my TH400.
T5 from tremec is worth looking into. I requested a quote.
Last edited by Masonwader; 10-18-2016 at 10:36 PM.
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truckerlary (01-01-2019)
10-18-2016, 11:08 PM
#6
Le Mans Master
Hey hows it going. My guess is if they didn't like the 200 and 700 autos they aren't going to be to crazy about the T5 either....but its a nice little trans for a 5 speed swap.
I did an auto to T5 conversion also and couldn't be happier with the results.
For the $$$ you cant go wrong. Good luck.
I did an auto to T5 conversion also and couldn't be happier with the results.
For the $$$ you cant go wrong. Good luck.
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JediOsborn (10-07-2022)
10-19-2016, 01:08 AM
#7
Burning Brakes
FWIW, there are a ton of owners here with TH200R4 or 700R4 transmissions. There are cars with well over 500HP with them. Your experts aren't very expert.
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10-19-2016, 01:42 AM
#8
Race Director
My advice is to visit a several shops and talk to several experts. Go to car shows and not only talk to corvette owners but ask anyone with a GM product, even the hot rod guys who own drivers and not trailer queens towed into the shows. You've made a good couple of starts by posting a thread here and talking to an expert you trust. I'm going to swap out my TH400 for either a beefed up auto overdrive or a TKO600. I'm still researching, but don't want to run 3000 rpm once I've rebuilt my drive train. Good luck!
10-19-2016, 05:34 AM
#9
Burning Brakes
Hey ya'll.
Just wanted to pass along my experience in case anyone wants the information in the future but doesn't happen along a great mechanic like I have.
I decided to look for a transmission to swap into my 74 L82 in order to gain an overdrive. My goal would be to lower rpm at highway speed while not losing low speed 'fun factor'. I've read all the forums and do it yourself guides on 200R4 vs 700R4 swaps. I have a stock engine and decided to find a 200R4 because I am not making a ton of horsepower and I have a 4.11 rear diff (which allegedly lines up better with the 4.11).
I found a shop in my area that specifically works with performance classic cars and vettes and gave the guy a call. I told him that I had been shopping the transmissions listed above. He was receptive to what I had planned (in terms of goals) but then offered feedback. Yes the 200R4 would be a great transmission now, but if I ever decided to build horsepower into the engine then I would end up needing another swap. He recommended an 4L60E although he told me the price would be twice as much. As an alternative he agreed that the 700R4 would go into my car with minimal modification for a good price and that it should be paired with a 3.55 or 3.08 rear diff change over if I wanted to really have a good road car and had no need of racing application. Overall he has been in business for over 20 years and has built many corvettes for various purposes, but alleges that no one is ever truly happy with a 200R4 or 700R4.
He pointed me to his transmission source who I called next.
Upon calling the transmission guy I was initially told I would not buy a 200 or 700 transmission from his shop. Some numbers included the torque rating which on the TH400 I have now is 80 and the torque rating on the 200 and 700 is 60, therefore they are substandard transmissions. He then explained that over the years he has sold and allowed many of these remanufactured transmissions to be placed in street and performance applications. I was told that they would never shift correctly, however, and that in order to get their internals to shift in a manner that would be pleasing it would put the internal pressures at levels that result in fast breakdown of the components. These transmissions would never mate to my throttle correctly and would always seek internals on my motor that don't exist. Lastly, 4th gear lockouts are finicky and he said that most people end up with nonsensical 1st and 2nd gears and then issues going into 3rd or 4th gear. He pleaded that I listen to quotes for a 4L60E and so I did.
Maybe I turned a blind eye to the electronic transmissions because I thought they were too expensive when I began my research, but I have to say this has been eye opening. Both of these guys could have taken my money and dropped either of those transmissions in my car. Neither of them want to allow it and they have both pushed for a 4L60E if I must have an overdrive. It was also highly recommended that I simply swap out my 4.11 rear end for a 3.08 and keep the TH400. I think I'm going to go that route.
I know this subject is beating a dead horse, but I wanted to put my experience out there for others looking to read as much as possible.
Just wanted to pass along my experience in case anyone wants the information in the future but doesn't happen along a great mechanic like I have.
I decided to look for a transmission to swap into my 74 L82 in order to gain an overdrive. My goal would be to lower rpm at highway speed while not losing low speed 'fun factor'. I've read all the forums and do it yourself guides on 200R4 vs 700R4 swaps. I have a stock engine and decided to find a 200R4 because I am not making a ton of horsepower and I have a 4.11 rear diff (which allegedly lines up better with the 4.11).
I found a shop in my area that specifically works with performance classic cars and vettes and gave the guy a call. I told him that I had been shopping the transmissions listed above. He was receptive to what I had planned (in terms of goals) but then offered feedback. Yes the 200R4 would be a great transmission now, but if I ever decided to build horsepower into the engine then I would end up needing another swap. He recommended an 4L60E although he told me the price would be twice as much. As an alternative he agreed that the 700R4 would go into my car with minimal modification for a good price and that it should be paired with a 3.55 or 3.08 rear diff change over if I wanted to really have a good road car and had no need of racing application. Overall he has been in business for over 20 years and has built many corvettes for various purposes, but alleges that no one is ever truly happy with a 200R4 or 700R4.
He pointed me to his transmission source who I called next.
Upon calling the transmission guy I was initially told I would not buy a 200 or 700 transmission from his shop. Some numbers included the torque rating which on the TH400 I have now is 80 and the torque rating on the 200 and 700 is 60, therefore they are substandard transmissions. He then explained that over the years he has sold and allowed many of these remanufactured transmissions to be placed in street and performance applications. I was told that they would never shift correctly, however, and that in order to get their internals to shift in a manner that would be pleasing it would put the internal pressures at levels that result in fast breakdown of the components. These transmissions would never mate to my throttle correctly and would always seek internals on my motor that don't exist. Lastly, 4th gear lockouts are finicky and he said that most people end up with nonsensical 1st and 2nd gears and then issues going into 3rd or 4th gear. He pleaded that I listen to quotes for a 4L60E and so I did.
Maybe I turned a blind eye to the electronic transmissions because I thought they were too expensive when I began my research, but I have to say this has been eye opening. Both of these guys could have taken my money and dropped either of those transmissions in my car. Neither of them want to allow it and they have both pushed for a 4L60E if I must have an overdrive. It was also highly recommended that I simply swap out my 4.11 rear end for a 3.08 and keep the TH400. I think I'm going to go that route.
I know this subject is beating a dead horse, but I wanted to put my experience out there for others looking to read as much as possible.
Remember, your 'great mechanics' are in business to make money, and selling up is a time honored way of making the next boat payment.
10-19-2016, 07:08 AM
#10
Drifting
Your mechanic is sadly mistaken....700r4s just need a little upgrade to handle big power.... I have had a 700r4 behind my 525HP 383 for 9 years... you need a qualified trans guy who can build it correctly [ stick with 87 or later models] for you or just order one from any of the experienced rebuilders like Bow-Tie Overdrives, or Monster Transmissions , TCI, etc ...with a 3 yr warrenty .... Not a difficult conversion..You will love it
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Stormin_Normin (10-12-2022)
10-19-2016, 10:07 AM
#11
Safety Car
THE PERFECT IS THE ENEMY OF THE GOOD. The 4L60E with appropriate controller is the "perfect". It can be made to do a great many things, BUT, it will require the same modifications to your C3 as the 700R4 and the whole thing is $$$$$$$$$$. You can put a late 700R4 in and it will perform well, AND replace the 4.11 rear with 3.36 or 3.55 all for less than the "perfect. OR you can drop in a beefed 200R4 without chassis mods, change your 4.11's to 3.55 or 3.70 and it will perform well. Remember, the 700R4 was used in many C4's (which put out huge torque numbers) and the 200R4 was used in the Buick Grand National, which also had more performance than your C3.
Remember, your 'great mechanics' are in business to make money, and selling up is a time honored way of making the next boat payment.
Remember, your 'great mechanics' are in business to make money, and selling up is a time honored way of making the next boat payment.
But I would keep the 4.11 and see how it turns out. I think a TH2004R can handle a 4.11
If not, then replace it.
I would never go from 4.11 to 3.08 with a std. L82
You will for sure loss performance.
If it's was my car, then a TH2004R and 4.11 (or 3.70)
10-19-2016, 09:38 PM
#12
Drifting
I certainly considered this and maybe I will one day. For now my wife has to be able to back it out the driveway (she refused to learn stick when I had a standard 2011 camaro). I guess I really need to look into it more. Maybe I could get away with it if the price were right. I wouldn't be against doing the work to make it happen that's for sure. You've queued a whole new line of phone calls to all the guys above, haha.
Edit: apparently the wide ratio 4 speed has a 4th gear ratio of 1.0 which is the same as the 3rd gear on my TH400.
T5 from tremec is worth looking into. I requested a quote.
Edit: apparently the wide ratio 4 speed has a 4th gear ratio of 1.0 which is the same as the 3rd gear on my TH400.
T5 from tremec is worth looking into. I requested a quote.
10-20-2016, 11:14 AM
#13
Safety Car
My car is at the transmission shop right now getting a 700R4 installed to replace the Turbo 400 that works flawlessly.
The past 30 years of overdrive automatics have spoiled me... while I once never gave a passing thought to 3000 to 4000 rpm cruise speeds, now anything over 2000 rpm at cruise has been feeling like I'm wasting gas and wearing out my engine.
I'm looking forward to the additional gear reduction of the R4 in first and of course the overdrive in 4th. It should be a nice combination for my otherwise anemic L48/350 (which is also on the chopping block soon).
Anybody looking for a nice Turbo 400?
mardyn
The past 30 years of overdrive automatics have spoiled me... while I once never gave a passing thought to 3000 to 4000 rpm cruise speeds, now anything over 2000 rpm at cruise has been feeling like I'm wasting gas and wearing out my engine.
I'm looking forward to the additional gear reduction of the R4 in first and of course the overdrive in 4th. It should be a nice combination for my otherwise anemic L48/350 (which is also on the chopping block soon).
Anybody looking for a nice Turbo 400?
mardyn
10-20-2016, 11:54 AM
#14
Le Mans Master
10-20-2016, 05:49 PM
#16
Team Owner
If you have a stock '74 L-82 engine, there is nothing with a properly rebuilt 200-4R or 700-R4 transmission that should give you any trouble. Both are very capable of handling the torque of your engine.
If you want to drag race with it, you might want to order one that is built with some stronger parts and with a sturdier torque converter. If not, don't worry about any big upgrades. Any standard rebuilt unit will have the basic upgrades in it already. Either unit will require a lockup-clutch controller to manage the lockup clutch operating. DO NOT BUY INTO THE USE OF A TOGGLE SWITCH TO DO THIS!
Either of these transmissions can be set up to shift wherever you want by someone who knows what they are doing. Your mechanic might be good at many things, but his cautions about shift point setup convince me that he has no GOOD knowledge of setting up a hydraulic transmission correctly. I also believe that for 'general use', a 3.55 rear gear is as steep as you want to go with an overdrive transmission. Any higher than that and you will be back in the situation of having high rpm's at highway speed. I have a 3.36 rear gear with a 700-R4 and run 70 mph at 2050 rpm. It would run about 2200 or so with a 3.55 gear. I like the comfort and engine ease at 2000 rpm at highway speeds.
Lastly, putting a 4L60E unit in your car might meet the mechanic's goals, but it would be very costly, require some modification to the tunnel in your floor and would need a computer to manage it...not to mention needing electronic speed signals to have it operate properly.
I think it would be best for you to search out a more qualified installer for your transmission project. Putting a 4L60E in your car is overkill, IMO.
If you want to drag race with it, you might want to order one that is built with some stronger parts and with a sturdier torque converter. If not, don't worry about any big upgrades. Any standard rebuilt unit will have the basic upgrades in it already. Either unit will require a lockup-clutch controller to manage the lockup clutch operating. DO NOT BUY INTO THE USE OF A TOGGLE SWITCH TO DO THIS!
Either of these transmissions can be set up to shift wherever you want by someone who knows what they are doing. Your mechanic might be good at many things, but his cautions about shift point setup convince me that he has no GOOD knowledge of setting up a hydraulic transmission correctly. I also believe that for 'general use', a 3.55 rear gear is as steep as you want to go with an overdrive transmission. Any higher than that and you will be back in the situation of having high rpm's at highway speed. I have a 3.36 rear gear with a 700-R4 and run 70 mph at 2050 rpm. It would run about 2200 or so with a 3.55 gear. I like the comfort and engine ease at 2000 rpm at highway speeds.
Lastly, putting a 4L60E unit in your car might meet the mechanic's goals, but it would be very costly, require some modification to the tunnel in your floor and would need a computer to manage it...not to mention needing electronic speed signals to have it operate properly.
I think it would be best for you to search out a more qualified installer for your transmission project. Putting a 4L60E in your car is overkill, IMO.
Last edited by 7T1vette; 10-20-2016 at 05:52 PM.
10-21-2016, 12:24 PM
#17
Burning Brakes
no clue what your "trans guy" meant about torque being 80 and 60 and therefore substandard, seems like gibberish.
that said, the 4L60E has had it's share of problems over the production life, and is based almost entirely on the 700R4....so what you mainly gain is the electronics over using a TV cable...and a fatter shop bill.
that said, the 4L60E has had it's share of problems over the production life, and is based almost entirely on the 700R4....so what you mainly gain is the electronics over using a TV cable...and a fatter shop bill.
10-21-2016, 01:28 PM
#18
Safety Car
If a TH2004R will be installed with 3.08 gears then you have a drive line @ 8.4
In my mind, that is very low if I'm driving a Corvette.
And I also don't want to go down to "just over idle" when driving 70mph.
But we all wants something different, and that is cool :- )
09-22-2018, 02:39 PM
#19
Cruising
I'm currently talking to a local trans shop who does a lot of hot rod automatics her in town about replacing the 4-speed in my 73 big block car with a 700R4 because a disability has made using a clutch difficult and dangerous for me. My mechanic offered both the 4L60E and 700R4 as options for me with no cost difference between the two for my application. I'm going to settle on the 700R4 because I'm used to it's quirks in my 82 Collectors. Plus I want to keep away from possible electrical problems and stick with mechanical controls that I understand. I do find that the 700R4 seems to have a ridiculously small ratio difference between 1st and 2nd gear but I'm familure with the 700 now so this makes it a no brainer choice for me. Maybe this is because over the years I was used to skipping gears altogether when shifting my 4-speed. I'd often skip 2nd and do first to third or skip 3rd and go 2nd to 4th. I'll be mating the auto to a mildly built 454 with 3:36 rear gears and the my mechanic insures me that the 700r4 he will build won't have any problem in my setup.
One final comment. My mechanic here in Oregon told me that it's getting hard to find 700R4 cases out here anymore but he had just found and bought a number of the from back east so he'd have a good case for me this winter.
One final comment. My mechanic here in Oregon told me that it's getting hard to find 700R4 cases out here anymore but he had just found and bought a number of the from back east so he'd have a good case for me this winter.
09-22-2018, 08:56 PM
#20
Drifting
Money saved on gas is one thing and does help justify a transmission swap. My biggest concern is wanting to take the car a 70 mile drive on the interstate to see family which I like to do every few weekends. I don't think screaming at 3500 rpm + at 70 mph for over an hour is good for the longevity of the car (or so I've been advised).
Try a gear change to 3:73s, This will keep the fun factor, plus drop the rpm's a few. might make it enjoyable for you.