Transmission swap
Thread Starter
8th Gear
Joined: Apr 2012
Posts: 8
Likes: 0
Transmission swap
I have a 79' L82 with 350 cu in motor and automatic 3 speed transmission.
I would like to install a 4 or 5 speed automatic transmission with overdrive.
Does anyone know if there is one that fits current torque converter and with out having to change drive shaft length?
Thanks
I would like to install a 4 or 5 speed automatic transmission with overdrive.
Does anyone know if there is one that fits current torque converter and with out having to change drive shaft length?
Thanks
Last edited by Dblancha; Apr 22, 2012 at 07:06 PM.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Melting Slicks
Joined: Dec 2009
Posts: 3,229
Likes: 656
From: Thunder Bay
I did the 700R-4 swap. Its nice because you can use a lot of factory parts if you get the right tailshaft housing, since the factory put them in these cars in '82. Oldalaskaman is right. Been discussed a gazillion times on this forum. Do a search.
Burning Brakes
Joined: Apr 2007
Posts: 1,039
Likes: 62
From: Kona Hawaii
Match your rear gears with the trans for best results......
From Bowtie OD:
The first gear ratio of a TH-700R4 is 3.06 to 1. This is 21% lower than the first gear ratio in a TH-350 ( 2.52 to 1). First gear ratio of the Th-700R4 is 23% lower than a TH-400 ( 2.48 to 1 ). Maybe the following example will help you make sense of this. These examples don't take into account any torque multiplication may be occurring through the torque converter, they are just to illustrate the numerical gear multiplication. The subject vehicle is a 1960s classic car with a 3.08:1 rear end. With a TH-350 you multiply the 2.52 first gear times the rear end ratio of 3.08 and you come up with a torque multiplication number of 7.76 to 1. If you are accelerating and your motor was developing 100 lbs. of torque at that moment, your rear tires have 776 lbs. of torque applied to it. (7.76 x 100 lbs = 776 lbs). With a TH-400 you multiply the 2.48 first gear ratio times the rear end ratio of 3.08 and you come up with a torque multiplication number of 7.64. If your motor were developing 100 lbs. of torque, your rear tire could have 764 lbs. of torque applied to it at that moment. (7.64 x 100 lbs = 764 lbs) With a TH-700R4 you multiply the 3.06 first gear ratio times the rear end ratio of 3.08 and you come up with a torque multiplication number of 9.42. If your motor were developing 100 lbs. of torque, your rear tire could have 942 lbs. of torque applied to it at that moment. (9.42 X 100 lbs = 9.42 lbs).
Conclusion
This car would feel 166 pounds more torque with the Th-700R4 transmission then a TH-350 in first gear and 178 pounds more torque than the TH-400 in first gear. To have the same torque multiplication with the TH-350 or TH-400 we would have to run a 3.73:1 rear end ratio. Now with the TH-350 first gear of 2.52 x 3.73 = 9.40 x 100 lbs of torque produced by the motor = 940 lbs felt at the tire. Also the TH-400 first gear of 2.48 x 3.73 = 9.25 x 100 lbs of torque produced by the motor = 925 lbs felt at the tire. If you have any Hot Rod blood running through your veins, this has to sound like fun running around town on Friday night. If you were looking to lower cruise RPM we just went the wrong way with this example. Running a 3.73 to 1 rear end gear ratio sure won't help gas mileage or lower your cruise RPM down the highway. With a 26" diameter tire and 3.73:1 rear end with the transmission in 1 to 1 third gear like the TH-350 or TH-400 in high gear, your engine would be turning approximately 2889 RPM at 60 MPH. This is not a pretty picture!
Solution
Install a TH-700R4 with these existing 3.08 rear end gears. This car will launch like a TH-350 or TH-400 with 3.73:1 rear end ears, so you can now have your stop light fun. When the Th-700R4 goes into fourth gear, your final drive ratio will be 2.16:1. (3.08:1 rear end ratio x .70:1 4th gear ratio in the Th-700R4 = 2.16:1 overall final drive ratio) With a 26" diameter tire, a 3.08:1 rear end ratio and the Th-700R4 in .70:1 fourth gear, your engine would be turning only 1670 RPM at 60 MPH. This is a pretty picture!
Automatic Transmission Gear Ratios
1st 2nd 3rd 4th Reverse
GM
Powerglide 1.76 1.00 1.76
TH350 2.52 1.52 1.00 1.93
TH400 2.48 1.48 1.00 2.00
200r4 2.74 1.57 1.00 0.67 2.07
700r4 3.06 1.62 1.00 0.70 2.29
4L60E 3.06 1.62 1.00 0.70 2.29
4L80E 2.48 1.48 1.00 0.75 2.08
What's your rear end ratio?
From Bowtie OD:
The first gear ratio of a TH-700R4 is 3.06 to 1. This is 21% lower than the first gear ratio in a TH-350 ( 2.52 to 1). First gear ratio of the Th-700R4 is 23% lower than a TH-400 ( 2.48 to 1 ). Maybe the following example will help you make sense of this. These examples don't take into account any torque multiplication may be occurring through the torque converter, they are just to illustrate the numerical gear multiplication. The subject vehicle is a 1960s classic car with a 3.08:1 rear end. With a TH-350 you multiply the 2.52 first gear times the rear end ratio of 3.08 and you come up with a torque multiplication number of 7.76 to 1. If you are accelerating and your motor was developing 100 lbs. of torque at that moment, your rear tires have 776 lbs. of torque applied to it. (7.76 x 100 lbs = 776 lbs). With a TH-400 you multiply the 2.48 first gear ratio times the rear end ratio of 3.08 and you come up with a torque multiplication number of 7.64. If your motor were developing 100 lbs. of torque, your rear tire could have 764 lbs. of torque applied to it at that moment. (7.64 x 100 lbs = 764 lbs) With a TH-700R4 you multiply the 3.06 first gear ratio times the rear end ratio of 3.08 and you come up with a torque multiplication number of 9.42. If your motor were developing 100 lbs. of torque, your rear tire could have 942 lbs. of torque applied to it at that moment. (9.42 X 100 lbs = 9.42 lbs).
Conclusion
This car would feel 166 pounds more torque with the Th-700R4 transmission then a TH-350 in first gear and 178 pounds more torque than the TH-400 in first gear. To have the same torque multiplication with the TH-350 or TH-400 we would have to run a 3.73:1 rear end ratio. Now with the TH-350 first gear of 2.52 x 3.73 = 9.40 x 100 lbs of torque produced by the motor = 940 lbs felt at the tire. Also the TH-400 first gear of 2.48 x 3.73 = 9.25 x 100 lbs of torque produced by the motor = 925 lbs felt at the tire. If you have any Hot Rod blood running through your veins, this has to sound like fun running around town on Friday night. If you were looking to lower cruise RPM we just went the wrong way with this example. Running a 3.73 to 1 rear end gear ratio sure won't help gas mileage or lower your cruise RPM down the highway. With a 26" diameter tire and 3.73:1 rear end with the transmission in 1 to 1 third gear like the TH-350 or TH-400 in high gear, your engine would be turning approximately 2889 RPM at 60 MPH. This is not a pretty picture!
Solution
Install a TH-700R4 with these existing 3.08 rear end gears. This car will launch like a TH-350 or TH-400 with 3.73:1 rear end ears, so you can now have your stop light fun. When the Th-700R4 goes into fourth gear, your final drive ratio will be 2.16:1. (3.08:1 rear end ratio x .70:1 4th gear ratio in the Th-700R4 = 2.16:1 overall final drive ratio) With a 26" diameter tire, a 3.08:1 rear end ratio and the Th-700R4 in .70:1 fourth gear, your engine would be turning only 1670 RPM at 60 MPH. This is a pretty picture!
Automatic Transmission Gear Ratios
1st 2nd 3rd 4th Reverse
GM
Powerglide 1.76 1.00 1.76
TH350 2.52 1.52 1.00 1.93
TH400 2.48 1.48 1.00 2.00
200r4 2.74 1.57 1.00 0.67 2.07
700r4 3.06 1.62 1.00 0.70 2.29
4L60E 3.06 1.62 1.00 0.70 2.29
4L80E 2.48 1.48 1.00 0.75 2.08
What's your rear end ratio?
Last edited by iokepakai; Apr 23, 2012 at 04:05 PM.
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Thread Starter
8th Gear
Joined: Apr 2012
Posts: 8
Likes: 0
Match your rear gears with the trans for best results......
From Bowtie OD:
The first gear ratio of a TH-700R4 is 3.06 to 1. This is 21% lower than the first gear ratio in a TH-350 ( 2.52 to 1). First gear ratio of the Th-700R4 is 23% lower than a TH-400 ( 2.48 to 1 ). Maybe the following example will help you make sense of this. These examples don't take into account any torque multiplication may be occurring through the torque converter, they are just to illustrate the numerical gear multiplication. The subject vehicle is a 1960s classic car with a 3.08:1 rear end. With a TH-350 you multiply the 2.52 first gear times the rear end ratio of 3.08 and you come up with a torque multiplication number of 7.76 to 1. If you are accelerating and your motor was developing 100 lbs. of torque at that moment, your rear tires have 776 lbs. of torque applied to it. (7.76 x 100 lbs = 776 lbs). With a TH-400 you multiply the 2.48 first gear ratio times the rear end ratio of 3.08 and you come up with a torque multiplication number of 7.64. If your motor were developing 100 lbs. of torque, your rear tire could have 764 lbs. of torque applied to it at that moment. (7.64 x 100 lbs = 764 lbs) With a TH-700R4 you multiply the 3.06 first gear ratio times the rear end ratio of 3.08 and you come up with a torque multiplication number of 9.42. If your motor were developing 100 lbs. of torque, your rear tire could have 942 lbs. of torque applied to it at that moment. (9.42 X 100 lbs = 9.42 lbs).
Conclusion
This car would feel 166 pounds more torque with the Th-700R4 transmission then a TH-350 in first gear and 178 pounds more torque than the TH-400 in first gear. To have the same torque multiplication with the TH-350 or TH-400 we would have to run a 3.73:1 rear end ratio. Now with the TH-350 first gear of 2.52 x 3.73 = 9.40 x 100 lbs of torque produced by the motor = 940 lbs felt at the tire. Also the TH-400 first gear of 2.48 x 3.73 = 9.25 x 100 lbs of torque produced by the motor = 925 lbs felt at the tire. If you have any Hot Rod blood running through your veins, this has to sound like fun running around town on Friday night. If you were looking to lower cruise RPM we just went the wrong way with this example. Running a 3.73 to 1 rear end gear ratio sure won't help gas mileage or lower your cruise RPM down the highway. With a 26" diameter tire and 3.73:1 rear end with the transmission in 1 to 1 third gear like the TH-350 or TH-400 in high gear, your engine would be turning approximately 2889 RPM at 60 MPH. This is not a pretty picture!
Solution
Install a TH-700R4 with these existing 3.08 rear end gears. This car will launch like a TH-350 or TH-400 with 3.73:1 rear end ears, so you can now have your stop light fun. When the Th-700R4 goes into fourth gear, your final drive ratio will be 2.16:1. (3.08:1 rear end ratio x .70:1 4th gear ratio in the Th-700R4 = 2.16:1 overall final drive ratio) With a 26" diameter tire, a 3.08:1 rear end ratio and the Th-700R4 in .70:1 fourth gear, your engine would be turning only 1670 RPM at 60 MPH. This is a pretty picture!
Automatic Transmission Gear Ratios
1st 2nd 3rd 4th Reverse
GM
Powerglide 1.76 1.00 1.76
TH350 2.52 1.52 1.00 1.93
TH400 2.48 1.48 1.00 2.00
200r4 2.74 1.57 1.00 0.67 2.07
700r4 3.06 1.62 1.00 0.70 2.29
4L60E 3.06 1.62 1.00 0.70 2.29
4L80E 2.48 1.48 1.00 0.75 2.08
What's your rear end ratio?
From Bowtie OD:
The first gear ratio of a TH-700R4 is 3.06 to 1. This is 21% lower than the first gear ratio in a TH-350 ( 2.52 to 1). First gear ratio of the Th-700R4 is 23% lower than a TH-400 ( 2.48 to 1 ). Maybe the following example will help you make sense of this. These examples don't take into account any torque multiplication may be occurring through the torque converter, they are just to illustrate the numerical gear multiplication. The subject vehicle is a 1960s classic car with a 3.08:1 rear end. With a TH-350 you multiply the 2.52 first gear times the rear end ratio of 3.08 and you come up with a torque multiplication number of 7.76 to 1. If you are accelerating and your motor was developing 100 lbs. of torque at that moment, your rear tires have 776 lbs. of torque applied to it. (7.76 x 100 lbs = 776 lbs). With a TH-400 you multiply the 2.48 first gear ratio times the rear end ratio of 3.08 and you come up with a torque multiplication number of 7.64. If your motor were developing 100 lbs. of torque, your rear tire could have 764 lbs. of torque applied to it at that moment. (7.64 x 100 lbs = 764 lbs) With a TH-700R4 you multiply the 3.06 first gear ratio times the rear end ratio of 3.08 and you come up with a torque multiplication number of 9.42. If your motor were developing 100 lbs. of torque, your rear tire could have 942 lbs. of torque applied to it at that moment. (9.42 X 100 lbs = 9.42 lbs).
Conclusion
This car would feel 166 pounds more torque with the Th-700R4 transmission then a TH-350 in first gear and 178 pounds more torque than the TH-400 in first gear. To have the same torque multiplication with the TH-350 or TH-400 we would have to run a 3.73:1 rear end ratio. Now with the TH-350 first gear of 2.52 x 3.73 = 9.40 x 100 lbs of torque produced by the motor = 940 lbs felt at the tire. Also the TH-400 first gear of 2.48 x 3.73 = 9.25 x 100 lbs of torque produced by the motor = 925 lbs felt at the tire. If you have any Hot Rod blood running through your veins, this has to sound like fun running around town on Friday night. If you were looking to lower cruise RPM we just went the wrong way with this example. Running a 3.73 to 1 rear end gear ratio sure won't help gas mileage or lower your cruise RPM down the highway. With a 26" diameter tire and 3.73:1 rear end with the transmission in 1 to 1 third gear like the TH-350 or TH-400 in high gear, your engine would be turning approximately 2889 RPM at 60 MPH. This is not a pretty picture!
Solution
Install a TH-700R4 with these existing 3.08 rear end gears. This car will launch like a TH-350 or TH-400 with 3.73:1 rear end ears, so you can now have your stop light fun. When the Th-700R4 goes into fourth gear, your final drive ratio will be 2.16:1. (3.08:1 rear end ratio x .70:1 4th gear ratio in the Th-700R4 = 2.16:1 overall final drive ratio) With a 26" diameter tire, a 3.08:1 rear end ratio and the Th-700R4 in .70:1 fourth gear, your engine would be turning only 1670 RPM at 60 MPH. This is a pretty picture!
Automatic Transmission Gear Ratios
1st 2nd 3rd 4th Reverse
GM
Powerglide 1.76 1.00 1.76
TH350 2.52 1.52 1.00 1.93
TH400 2.48 1.48 1.00 2.00
200r4 2.74 1.57 1.00 0.67 2.07
700r4 3.06 1.62 1.00 0.70 2.29
4L60E 3.06 1.62 1.00 0.70 2.29
4L80E 2.48 1.48 1.00 0.75 2.08
What's your rear end ratio?
Melting Slicks
Joined: Dec 2009
Posts: 3,229
Likes: 656
From: Thunder Bay
Funny you should say that...
I have 3.55 gears in my '79 with the 700R4. First gear is a little too deep. From a pure gear ratio standpoint, you might be better off with the 200-4R. I can't say how it fits, although others on this forum swear by it. I just like the 700R-4 because it is a nice clean installation. If you get the factory parts its a bolt in and I like stuff that looks factory.
Great info from iokepakai. I learned a few things.
I have 3.55 gears in my '79 with the 700R4. First gear is a little too deep. From a pure gear ratio standpoint, you might be better off with the 200-4R. I can't say how it fits, although others on this forum swear by it. I just like the 700R-4 because it is a nice clean installation. If you get the factory parts its a bolt in and I like stuff that looks factory.
Great info from iokepakai. I learned a few things.
Burning Brakes
Joined: Apr 2007
Posts: 1,039
Likes: 62
From: Kona Hawaii
With that 3.55 ratio a 200r4 would be a good choice.Check out Bowtie Overdrives,they have a tubular crossmember for the C3 that bolts up.I think you can use your existing driveshaft with no mods.Did the trans swap thing last year.After much research decided to go Richmond 6 spd due to my 3.08 rear gears and I liked the idea of a manual over an automatic.The gear spacing is just about perfect no large drops of rpm's.Fuel mileage has improved to 20 mpg's on the highway.
Just about the best change with the Vette so far.....
Just about the best change with the Vette so far.....
Melting Slicks
Joined: Dec 2009
Posts: 3,229
Likes: 656
From: Thunder Bay
With that 3.55 ratio a 200r4 would be a good choice.Check out Bowtie Overdrives,they have a tubular crossmember for the C3 that bolts up.I think you can use your existing driveshaft with no mods.Did the trans swap thing last year.After much research decided to go Richmond 6 spd due to my 3.08 rear gears and I liked the idea of a manual over an automatic.The gear spacing is just about perfect no large drops of rpm's.Fuel mileage has improved to 20 mpg's on the highway.
Just about the best change with the Vette so far.....
Just about the best change with the Vette so far.....
Melting Slicks
Joined: Mar 2008
Posts: 2,989
Likes: 198
From: Meriden CT
With that 3.55 ratio a 200r4 would be a good choice.Check out Bowtie Overdrives,they have a tubular crossmember for the C3 that bolts up.I think you can use your existing driveshaft with no mods.Did the trans swap thing last year.After much research decided to go Richmond 6 spd due to my 3.08 rear gears and I liked the idea of a manual over an automatic.The gear spacing is just about perfect no large drops of rpm's.Fuel mileage has improved to 20 mpg's on the highway.
Just about the best change with the Vette so far.....
Just about the best change with the Vette so far.....
