Shift Kit:
Thread Starter
Instructor
Joined: Jan 2009
Posts: 163
Likes: 1
From: Port Allen Louisiana
Shift Kit:
My transmission is needing to be rebuilt. Turbo auto 350. 1980 Corvette, L82.. Could I get some help on the Pros and Cons of rebuilding the transmission with a shift kit. I really know nothing about what a shift is and actually does for the transmission. Also, would anything have to be done about the torque convertor? I have a local guy who knows what he is doing with transmissions. Just looking for second opinions. Thanks for any help.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,112
From: Crossville TN
Instead of rebuilding that old THM-350, why not swap it out for an overdrive trans with lockup...i.e. 700R-4. You can have the 700 upgraded with a shift kit, if you want. But you will end up with a ride which will get 20+% better fuel mileage on the highway and will run at 2100 rpm at 70mph. It will be much more pleasant to drive at highway speeds!! 
If the trans needs a full rebuild, you will never have a better opportunity to upgrade the transmission in your car.
If the trans needs a full rebuild, you will never have a better opportunity to upgrade the transmission in your car.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,062
From: altered state
St. Jude Donor '05
used the B and M kit on my T350s, used the step below full comp mode, loved it.
Nice firm shift on normal driving, 1-2 always barked if I was getting into the pedal.
There are more advanced kits but that one is affordable, a monkey can install it, suited my needs.
Nice firm shift on normal driving, 1-2 always barked if I was getting into the pedal.
There are more advanced kits but that one is affordable, a monkey can install it, suited my needs.
Melting Slicks
Joined: Dec 2009
Posts: 3,195
Likes: 632
From: Thunder Bay
I had a shift kit in the TH350 in my '79 and I agree it was awesome. Transmission guys also tell me it's actually easier on the trans. But I do have to agree with 7T1vette. I swapped the 350 for a 700R4 and it was a huge improvement in driveability and mileage. My only complaint with that trans was that first gear was too low. I understand a 200-4R might be a better choice in a 4 speed automatic.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,062
From: altered state
St. Jude Donor '05
Heard the same also as the clutches slip a hair less ea shift.
Trans guy harped on me for yrs to only use D for around town driving with 700rs, 4l60e etc; only use OD on the highway.
I found my mpg on a heavy 1500 lb truck was exactly the same on the hwy at 60 in D vs OD...over that OD came in handy..
Less slippage and lasts longer, cooler is a plus
There are some good trans guys on the forum maybe they can pop in.
Trans guy harped on me for yrs to only use D for around town driving with 700rs, 4l60e etc; only use OD on the highway.
I found my mpg on a heavy 1500 lb truck was exactly the same on the hwy at 60 in D vs OD...over that OD came in handy..
Less slippage and lasts longer, cooler is a plus
There are some good trans guys on the forum maybe they can pop in.
Drifting
Joined: Aug 2019
Posts: 1,506
Likes: 495
the only con is if you get/.purchase a kit that shifts hard all the time , even when driving easy .
On my 1980 L82 I went with a 700R4 , the 700 has a 3.06 first gear that works great with the 3.08 rear gear in the 1980 differential and the 1980 Lock up wiring hardware works perfect on a 700R4 . A transmission crossmember , shifter modification , 3 inch shorter driveshaft and a TV cable will be required to switch over
On my 1980 L82 I went with a 700R4 , the 700 has a 3.06 first gear that works great with the 3.08 rear gear in the 1980 differential and the 1980 Lock up wiring hardware works perfect on a 700R4 . A transmission crossmember , shifter modification , 3 inch shorter driveshaft and a TV cable will be required to switch over
Thread Starter
Instructor
Joined: Jan 2009
Posts: 163
Likes: 1
From: Port Allen Louisiana
Instead of rebuilding that old THM-350, why not swap it out for an overdrive trans with lockup...i.e. 700R-4. You can have the 700 upgraded with a shift kit, if you want. But you will end up with a ride which will get 20+% better fuel mileage on the highway and will run at 2100 rpm at 70mph. It will be much more pleasant to drive at highway speeds!!
If the trans needs a full rebuild, you will never have a better opportunity to upgrade the transmission in your car.
If the trans needs a full rebuild, you will never have a better opportunity to upgrade the transmission in your car.
Melting Slicks
Joined: Dec 2015
Posts: 3,181
Likes: 732
From: Texas City, TX Texas
You can get a new 700R-4 for about a grand, I REALLY wish I had overdrive...
P.S. I have put shift kits in my automatic cars for many years, makes even a mild V8 much more fun to drive. Cheap and easy.
P.S. I have put shift kits in my automatic cars for many years, makes even a mild V8 much more fun to drive. Cheap and easy.
Last edited by Richard Daugird; Mar 26, 2021 at 04:44 PM.
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Race Director
Joined: Mar 2017
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From: Virginia
If you are looking at spending $2700 and pulling the transmission, consider spending a bit more (perhaps twice more), and adding a third pedal (and overdrive).
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,112
From: Crossville TN
Most transmission rebuild facilities will take your 350 in trade for a 700-R...so you will lessen the expense somewhat. They can rebuild your 350 and sell it to someone else.
Price of labor these days is more than seems reasonable...but time marches on. If you can do the swap, you can save a lot of $$$. If not, making the swap is still the best choice. It will make your car much more attractive, should you decide to sell it.
Price of labor these days is more than seems reasonable...but time marches on. If you can do the swap, you can save a lot of $$$. If not, making the swap is still the best choice. It will make your car much more attractive, should you decide to sell it.
Melting Slicks
Joined: Dec 2015
Posts: 3,181
Likes: 732
From: Texas City, TX Texas