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I've recently been thinking about swapping the stock TH350 in my 1980 to a Muncie 4 Speed transmission. Could people with experience doing swaps similar to this give me some insight into what exactly it would entail and where I could get the parts to do it? Is it even worth the time and money to do this swap? Thanks
I would do it. Rounding up all the correct parts may be challenging. Muncies come with to 2 input shaft sizes and 2 output sizes. If you are going to use your turbo 350 driveshaft you need a 27 spline output shaft. They also come with 32 spline which is the same as a turbo 400. Input sizes are 10 spline and 26 fine spline. The muncie is probably going to be an easy find. The correct shifter and linkage may be a little harder to find.
As the proud owner of one of the few 80s that came with a 4-speed, I wouldn't bother. A manual makes the car about a million times more fun to drive. But, for the same amount of effort and some more money, you could have a 5 speed instead, like a TKX, ot even a T56 6-speed.
I'm contemplating upgrading myself.
Take a look at Silver State Transmission's website (SST), and look for threads by @Gordonm, who has done a bunch of swaps.
As somebody who has done this to my 1980 I can say that replacing the Peddle assembly is a full 50 percent of the work involved. Make sure there is a working Clutch Switch before you install ! You will probably want to replace the Crossmember and put a real Duel Exhaust on at the same time.
For me, driving a Corvette mandates a manual transmission. It would not be as fun without it. Check out the Classified section. I am selling both a Borg Super T-10 out of my 77, and a Muncie M20 out of my 69. I am upgrading to Autogear M23 4 speeds because of the power and torque levels of the engine I am running. I considered TKX,.....but the cost is significantly higher, and I like the original shifter and character of the 4 speed transmissions.
Z-Bar (requires welding) or Hydraulic Throw out bearing
Clutch
Vette Bellhousing
11" flywheel
Transmission - Muncie M-20 or M-21 or Super T-10
Driveshaft with matching trans yoke
Shifter
Crossmember bracket and/or crossmember
Then there is the rear gear. What rear gear do you have? Many autos have 3.08 to 2.78 or so. Pick your trans carefully so first gear is not a dog. 1st gear ratios run from 2.20 to 2.87 or so. My factory BB gear setup is 2.20 (C.R.) x 3.36 rear and at only 7.4 total it feels like it is starting off in second all the time. I am changing that. 9:1 or 10:1 in 1st is much more "lively".
If all stock, you should have a 3.07 rear now, and the TH350 has a 2.5 1st, for an overall of 7.7 in first. If that is the case you do not want a M-21 close ratio (2.20) trans. The M-20 has a 2.52 1st. The Super T-10s were even better at around 2.88. That would be 8.8 overall which would feel great. That would handle a mild to medium motor. If you have a real strong engine consider the Autogear trans for strength.
You are starting with an auto which already has a bolt-in crossmember. So that's a plus.
But I agree Vettes and sticks just go together. It's worth the effort.
Last edited by leigh1322; Apr 21, 2022 at 08:06 AM.
Z-Bar (requires welding) or Hydraulic Throw out bearing
Clutch
Vette Bellhousing
11" flywheel
Transmission - Muncie M-20 or M-21 or Super T-10
Driveshaft with matching trans yoke
Shifter
Crossmember bracket and/or crossmember
Then there is the rear gear. What rear gear do you have? Many autos have 3.08 to 2.78 or so. Pick your trans carefully so first gear is not a dog. 1st gear ratios run from 2.20 to 2.87 or so. My factory BB gear setup is 2.20 (C.R.) x 3.36 rear and at only 7.4 total it feels like it is starting off in second all the time. I am changing that. 9:1 or 10:1 in 1st is much more "lively".
If all stock, you should have a 3.07 rear now, and the TH350 has a 2.5 1st, for an overall of 7.7 in first. If that is the case you do not want a M-21 close ratio (2.20) trans. The M-20 has a 2.52 1st. The Super T-10s were even better at around 2.88. That would be 8.8 overall which would feel great. That would handle a mild to medium motor. If you have a real strong engine consider the Autogear trans for strength.
You are starting with an auto which already has a bolt-in crossmember. So that's a plus.
But I agree Vettes and sticks just go together. It's worth the effort.
Much appreciated, this list is gonna help me out a ton if I decide to go through with this swap.
One word-OVERDRIVE!!! I wish I'd converted to O.D. when I had mine apart. I hate the high RPMs on the highway. Would NEVER consider a four speed again.
I have a 3.36 rear in my 1968 C3 and it is great as even on the highways as it is not screaming along. Now my buddies with their 4.11 rears have to deal with terrible gas mileage and the screaming engine at 70 mph. IF I were building a new system I would probably change the gears inside my Muncie and have 4th gear be a slight over-drive. At 70 mph I get good mileage and with the 427 my 0-60's can embarrass many European cars.
At at Drag strip I was able to beat several 4.11 rear Corvettes including a factory stock L89 with my 3.36. I drove 60 miles to the strip and raced all day and still had plenty of gas to drive home without visiting a gas station.
If gas prices stay where they are (thanks to sleepy joe) it would be a great thing to have a serious over-drive. Starting from scratch I would agree with Bikespace!
Best regards,
Chris
The reason your '68 can perform with a 3.36 is because it has a big block! I'm guessing his '80 has no where near the torque you have. I only have 3.55s and even in the slow lane, with everyone passing me, I keep wishing I could grab another gear. If you are starting from scratch, there's no reason NOT to go with OD, except specific racing applications. The cost difference will be minimal. With OD, you can also then put in some 4.11s and it will feel like 100 extra horsepower.
My 80 has the stock 3.07 diff. First gear in the B&W Super T-10 is 2.88, for a total multiplication of 8.84 in first gear. That's plenty quick, and will easily spin tires if I want to (I never want to).
I strongly suggest the 5 or 6 speed because I still find myself reaching for 5th gear. The shifting is "classic", but very notchy, even with a Hurst shifter and synthetic gear oil. I'd prefer something better, with more gears.
The ratios are fine. I'd love a 0.8 OD gear (and possibly a 0.6 on top of that for 6th gear), with the other ratios as is. One of the three TKX ratios does exactly that: https://www.tremec.com/menu.php?m=184
I rarely exceed 60 mph in my Corvette. On the roads of PA, there is no need, or excuse, for doing so. So, a fifth gear does nothing for me, AND, for me, a modern transmission in my C3 Corvettes just takes away all the character of the car. If I wanted that modern technology, I would just by a C5 or C6. Maybe someday I will, but I doubt that those cars will ever be the experience I enjoy in my C3 Corvette. Others may disagree. But, its my world,....my car. The OP need to figure out his world. I'm also the guy who converted both brakes and steering from power to factory manual.....and would not have it any other way. The 77 is that way, the 69 will be that way.
And then there is the fact that a TKX tranmssion will cost me $1500 more than a Jody Haag Autogear M23 4 speed.
But heh......everybody likes different things. No right or wrong to it.
Alohas! Totally worth doing a manual swap.I have the Richmond six speed in mine with a 3.27 1st gear .With that first gear no need change my 3.08 rear gear.The car is pretty quick off the line .With the 6 speed trans I can always find the right gear.I would advise looking into a complete kit if you have the funds to do so.I did my parts list in increments ,it was costly and time consuming not to mention the shipping to Hawaii was stupid expensive.The Richmond trans fit perfectly and the driveshaft from the TH350 worked with the Richmond ,just needed to change the yoke.Not sure if the Richmond 6 speed is available anymore ,but there are some other 6 speeds or 5 speeds that might have that low 1st gear to work with your rear gear.Worst part of the job,as mentioned is the pedal bracket.Need to be patient and take breaks .After all said and done car is a blast to drive! https://www.corvetteforum.com/forums...am-change.html Good Luck with your swap if you choose to do so....
I've recently been thinking about swapping the stock TH350 in my 1980 to a Muncie 4 Speed transmission. Could people with experience doing swaps similar to this give me some insight into what exactly it would entail and where I could get the parts to do it? Is it even worth the time and money to do this swap? Thanks
I chose a different path and went with a Bow-Tie Overdrives 700R4 conversion. I got my '4-speed' but it is an automatic with overdrive. It has helped with acceleration.
If you do choose to go manual, consider the 5- or 6-speed Tremec conversions.
My 73 NEEDS a stick too. NEED. I will never enjoy driving an automatic. Only bought one because this was the only way into a steel bumper car with my welfare budget.
I'm leaning towards the Camaro T5 too. My budget is farcical, I spend a LOT ov time at speed (over 100mph), and gas is $7-8 a gallon here. There really is nothing else to think about. Should be a bit cheaper too.
I have been reading articles about transmission swaps for over a year off and on. It started when I was going to swap a 5-spd into the 82 CE I owned at the time. Ultimately decided and sold the CE then bought a 4-spd car. Now I am putting a T5 from a 1991 v-8 Firebird into my 75 4-spd car. T5 has 26 spline input and 27 spline output shafts. You will have more to do with the Auto to manual conversion and I am interested in your progress. I currently am over thinking the cutting of my welded in cross member for ease of the swap along with the t5 angled mount to cross member fit. I do have the Firebird tilted bellhousing, but I would prefer to use the straight one on my car to maintain clutch z bar the t-10 uses. My t-10 is making noise in 3 of the 4 gears and throw out bearing is also noisy. With the T5 having the internal rail shifter and able to handle 300 ft lbs torque, I think the T5 swap is a cleaner, easy, lowest price option as my stock motor is only running a true dual exhaust and 2101 intake with a quadrajet. Keep us updated!
you can't be effing around dry fitting that trans repeatedly over a fixed crossmember. it can be done bolt-in with a couple of short pieces of u-channel but better with a welder.. if you have a T5, like i do, by all means use it. they are getting like Fiero seats. few more out there. so i think looking for a T5 setup is a waste of time these days.
Last edited by derekderek; Apr 25, 2022 at 11:32 AM.
1980 Automatic to Manual Conversion
