Transmission advice.
Thread Starter
5th Gear
Joined: Apr 2013
Posts: 5
Likes: 0
Transmission advice.
Looking for some input. 1970 454 Muncie M20. All original #’s match, I mention this because of the couple questions i’m about to ask. I’v had the car for 25 years and it’s driven regularly. Finally have the time & money to get some things done. Motor was done 2 years ago and now time for trans. Looking for recommendations on a shop for rebuild. I’m in Chicago but have no problem driving 8-10 hours for a reputable shop.
Second question, I have been thinking about possibly going with a 5 speed trans kit. Curios to know just how difficult the install is. I’ve had the body off and done a lot of chassis work. If I go this route I would prefer not to pull the body again. I guess my question is, is it a nightmare or not that bad or somewhere in between? Any kit recommendations would be appreciated too. Finally pretty sure I remember reading somewhere this conversion requires cutting the tunnel, how bad will this effect the value do you guys think.
Second question, I have been thinking about possibly going with a 5 speed trans kit. Curios to know just how difficult the install is. I’ve had the body off and done a lot of chassis work. If I go this route I would prefer not to pull the body again. I guess my question is, is it a nightmare or not that bad or somewhere in between? Any kit recommendations would be appreciated too. Finally pretty sure I remember reading somewhere this conversion requires cutting the tunnel, how bad will this effect the value do you guys think.
Race Director
Joined: Mar 2017
Posts: 11,949
Likes: 4,507
From: Virginia
A TKX swap should not require cutting the tunnel, though you may want to, to get an oversized U-joint on the driveshaft. The driveshaft will likely need to be shortened.
Check out shiftsst.com for the kit. There are lots of videos on YouTube to give you an idea of how difficult it is. The biggest problem you face may be the welded transmission crossmember (which is not a problem for automatic cars, and all 80-82 cars).
Check out shiftsst.com for the kit. There are lots of videos on YouTube to give you an idea of how difficult it is. The biggest problem you face may be the welded transmission crossmember (which is not a problem for automatic cars, and all 80-82 cars).
Old Fart Pilot
Joined: Apr 2010
Posts: 1,921
Likes: 991
From: Spokane, WA
If you go with the 5-speed, would you do the swap or have a shop do it? I believe the 5-speed have fairly tight tolerances that might be hard to achieve with the body on. Haven't done it myself, so just be sure you know what you're getting into. As for value it really depends on what you want. The 5-speed will surely make it cruise easier but might lower the value to another buyer tyhat wants originality. If you go new, keep the M20 in case next owner wants it...
Melting Slicks
Joined: Nov 2006
Posts: 3,411
Likes: 1,821
From: Apple Valley, MN
As mentioned, you’ll need to decide what to do with the crossmember.
What differential ratio do you have? If you are running a 3:08 or 3:36, going through the motions of installing a 5 speed may not be worth it as the 5th gear is an overdrive. Very popular with a 3:70 ratio though.
What differential ratio do you have? If you are running a 3:08 or 3:36, going through the motions of installing a 5 speed may not be worth it as the 5th gear is an overdrive. Very popular with a 3:70 ratio though.
Racer
Joined: Dec 2022
Posts: 301
Likes: 87
As mentioned, you’ll need to decide what to do with the crossmember.
What differential ratio do you have? If you are running a 3:08 or 3:36, going through the motions of installing a 5 speed may not be worth it as the 5th gear is an overdrive. Very popular with a 3:70 ratio though.
What differential ratio do you have? If you are running a 3:08 or 3:36, going through the motions of installing a 5 speed may not be worth it as the 5th gear is an overdrive. Very popular with a 3:70 ratio though.
Melting Slicks
Joined: Aug 2016
Posts: 2,346
Likes: 1,174
From: CLEVELAND STUCK IN OHIO
2024 C3 of the Year Finalist- Modified
I installed the SST 5spd w/perfect fit kit and it fit perfectly . I modified the welded in crossmember myself, many options for that. New driveshaft came with the kit. Just double check your diff. and tire diameter to be sure your 454 likes the .68 O.D.
Forget the value aspect and enjoy the smiles per mile increase. Best cash I ever spent on mine….
.
Forget the value aspect and enjoy the smiles per mile increase. Best cash I ever spent on mine….
.
Melting Slicks
Joined: May 2004
Posts: 2,743
Likes: 843
From: Gulf of America
2023 C7 of the Year Finalist - Unmodified
2018 C3 of Year Finalist
Many years ago, I installed the Keisler TKO-600 5-speed with the .64 OD in my 4-speed '72.
That particular trans can be installed w/o cutting the crossmember. Don't know about the newer TKX.
Anyway, besides the new HP engine I installed, the 5-speed is the best thing I have done to my '72.
Did many Power Tours with my son and I can run with the newer Corvettes on the interstate.
That particular trans can be installed w/o cutting the crossmember. Don't know about the newer TKX.
Anyway, besides the new HP engine I installed, the 5-speed is the best thing I have done to my '72.
Did many Power Tours with my son and I can run with the newer Corvettes on the interstate.
Drifting
Joined: Aug 2010
Posts: 1,797
Likes: 304
From: Charlotte Area North Carolina
If you decide to keep the Muncie and just have it rebuilt, Ed Harnett runs a family-owned business that only rebuild Muncie's (M20-M21-M22). He is out of Lansdowne, PA. Much further than the 8-10 hour drive you mentioned but worth it if you decide to go that route. Ed's work phone is (610) 623-9381.
I decided to have my original rebuilt, happy about that decision. Ed is and old-school craftsman. If I recall correctly, Ed told me he and his son(s) do about 400 Muncie's per year. I phone interviewed many tranny rebuilders and decided to go with Ed because of his "Muncie only" buisness model. I was looking for top quality, craftsmanship, and wanted it done right. I didn't want my tranny rebuilt by someone who was half the age of my tranny and just replaces parts. I drove my tranny to Ed from N. Carolina. I just did not trust shippers with an OEM, numbers matching, nearly impossible to replace dated M-21 original.
Finally, I went the rebuild OEM route because I thought it best protected the value of my 1969 and it maintained my all original drivetrain status. Nothing to cut. No mods necessary.
I decided to have my original rebuilt, happy about that decision. Ed is and old-school craftsman. If I recall correctly, Ed told me he and his son(s) do about 400 Muncie's per year. I phone interviewed many tranny rebuilders and decided to go with Ed because of his "Muncie only" buisness model. I was looking for top quality, craftsmanship, and wanted it done right. I didn't want my tranny rebuilt by someone who was half the age of my tranny and just replaces parts. I drove my tranny to Ed from N. Carolina. I just did not trust shippers with an OEM, numbers matching, nearly impossible to replace dated M-21 original.
Finally, I went the rebuild OEM route because I thought it best protected the value of my 1969 and it maintained my all original drivetrain status. Nothing to cut. No mods necessary.
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Drifting
Joined: Nov 2002
Posts: 1,787
Likes: 261
From: Blue Bell PA
2018 C3 of Year Finalist
Ed comes highly recommended here on the forum for years. He has done 2 for me ,just
a great person. You will be happy with his work. He always talks about retiring so I would call him soon.
if you need his number let me know. He lives 1/2 from me,I was lucky.
a great person. You will be happy with his work. He always talks about retiring so I would call him soon.
if you need his number let me know. He lives 1/2 from me,I was lucky.
Race Director
Joined: Mar 2016
Posts: 14,402
Likes: 8,211
From: Napa Valley California
I swapped from an TH400 to a Tremec TKO 5 speed.
I purchased the Silver Sport Transmission kit and did the installation myself.
It was a breeze.
The only difference for you would be modifying the transmission crossmember, which has been done by many members on this forum.
SST may already have the kit as an option.
I believe the late David Howard did a full thread which included each step to make the modification easy.
As far as gearing you can get the five speed transmissions in either a short ratio or wide ratio.
Basically it’s the difference between having a .64 ratio fifth gear or a .82 ratio fifth gear so you can better match the cruising rpm at highway speeds.
You don’t need to swap rear ring and pinion gearing.
The SST kit also provides the driveshaft set up with the proper size U joints and SST guarantees that you will not need to modify the trans tunnel.
Only if you plan on racing or installing a monster torque beast engine would you need to increase the size of the U joints.
If you haven’t already blown U joints, swapping to a five speed won’t cause you to do so.
I purchased the Silver Sport Transmission kit and did the installation myself.
It was a breeze.
The only difference for you would be modifying the transmission crossmember, which has been done by many members on this forum.
SST may already have the kit as an option.
I believe the late David Howard did a full thread which included each step to make the modification easy.
As far as gearing you can get the five speed transmissions in either a short ratio or wide ratio.
Basically it’s the difference between having a .64 ratio fifth gear or a .82 ratio fifth gear so you can better match the cruising rpm at highway speeds.
You don’t need to swap rear ring and pinion gearing.
The SST kit also provides the driveshaft set up with the proper size U joints and SST guarantees that you will not need to modify the trans tunnel.
Only if you plan on racing or installing a monster torque beast engine would you need to increase the size of the U joints.
If you haven’t already blown U joints, swapping to a five speed won’t cause you to do so.
Melting Slicks
Joined: Jul 2006
Posts: 2,291
Likes: 493
From: Salmon Arm, BC
I have to agree with the others that 5 speed fantastic. I put a TKO 600 in with the .64 overdrive and it's likely the best mod I've ever done to my car. I installed it myself ( bought a kit from now defunct Classic Chevy 5 speeds) and installed the engine and trans as one unit using an engine lift. It completely transformed my car into a perfect driver, and freeway speeds (80 MPH) are a breeze now at 2100 RPM.
You won't regret making this change....
You won't regret making this change....